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@chapter Filtergraph description
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@c man begin FILTERGRAPH DESCRIPTION
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A filtergraph is a directed graph of connected filters. It can contain
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cycles, and there can be multiple links between a pair of
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filters. Each link has one input pad on one side connecting it to one
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filter from which it takes its input, and one output pad on the other
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side connecting it to the one filter accepting its output.
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Each filter in a filtergraph is an instance of a filter class
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registered in the application, which defines the features and the
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number of input and output pads of the filter.
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A filter with no input pads is called a "source", a filter with no
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output pads is called a "sink".
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@section Filtergraph syntax
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A filtergraph can be represented using a textual representation, which
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is recognized by the @code{-vf} and @code{-af} options of the ff*
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tools, and by the @code{av_parse_graph()} function defined in
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@file{libavfilter/avfiltergraph}.
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A filterchain consists of a sequence of connected filters, each one
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connected to the previous one in the sequence. A filterchain is
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represented by a list of ","-separated filter descriptions.
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A filtergraph consists of a sequence of filterchains. A sequence of
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filterchains is represented by a list of ";"-separated filterchain
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descriptions.
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A filter is represented by a string of the form:
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[@var{in_link_1}]...[@var{in_link_N}]@var{filter_name}=@var{arguments}[@var{out_link_1}]...[@var{out_link_M}]
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@var{filter_name} is the name of the filter class of which the
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described filter is an instance of, and has to be the name of one of
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the filter classes registered in the program.
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The name of the filter class is optionally followed by a string
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"=@var{arguments}".
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@var{arguments} is a string which contains the parameters used to
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initialize the filter instance, and are described in the filter
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descriptions below.
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The list of arguments can be quoted using the character "'" as initial
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and ending mark, and the character '\' for escaping the characters
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within the quoted text; otherwise the argument string is considered
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terminated when the next special character (belonging to the set
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"[]=;,") is encountered.
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The name and arguments of the filter are optionally preceded and
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followed by a list of link labels.
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A link label allows to name a link and associate it to a filter output
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or input pad. The preceding labels @var{in_link_1}
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... @var{in_link_N}, are associated to the filter input pads,
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the following labels @var{out_link_1} ... @var{out_link_M}, are
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associated to the output pads.
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When two link labels with the same name are found in the
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filtergraph, a link between the corresponding input and output pad is
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created.
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If an output pad is not labelled, it is linked by default to the first
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unlabelled input pad of the next filter in the filterchain.
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For example in the filterchain:
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@example
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nullsrc, split[L1], [L2]overlay, nullsink
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@end example
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the split filter instance has two output pads, and the overlay filter
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instance two input pads. The first output pad of split is labelled
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"L1", the first input pad of overlay is labelled "L2", and the second
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output pad of split is linked to the second input pad of overlay,
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which are both unlabelled.
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In a complete filterchain all the unlabelled filter input and output
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pads must be connected. A filtergraph is considered valid if all the
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filter input and output pads of all the filterchains are connected.
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Follows a BNF description for the filtergraph syntax:
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@example
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@var{NAME}             ::= sequence of alphanumeric characters and '_'
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@var{LINKLABEL}        ::= "[" @var{NAME} "]"
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@var{LINKLABELS}       ::= @var{LINKLABEL} [@var{LINKLABELS}]
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@var{FILTER_ARGUMENTS} ::= sequence of chars (eventually quoted)
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@var{FILTER}           ::= [@var{LINKNAMES}] @var{NAME} ["=" @var{ARGUMENTS}] [@var{LINKNAMES}]
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@var{FILTERCHAIN}      ::= @var{FILTER} [,@var{FILTERCHAIN}]
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@var{FILTERGRAPH}      ::= @var{FILTERCHAIN} [;@var{FILTERGRAPH}]
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@end example
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@c man end FILTERGRAPH DESCRIPTION
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@chapter Audio Filters
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@c man begin AUDIO FILTERS
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When you configure your FFmpeg build, you can disable any of the
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existing filters using --disable-filters.
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The configure output will show the audio filters included in your
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build.
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Below is a description of the currently available audio filters.
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@section anull
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Pass the audio source unchanged to the output.
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@c man end AUDIO FILTERS
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@chapter Audio Sources
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@c man begin AUDIO SOURCES
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Below is a description of the currently available audio sources.
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@section anullsrc
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Null audio source, never return audio frames. It is mainly useful as a
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template and to be employed in analysis / debugging tools.
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It accepts as optional parameter a string of the form
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@var{sample_rate}:@var{channel_layout}.
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@var{sample_rate} specify the sample rate, and defaults to 44100.
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@var{channel_layout} specify the channel layout, and can be either an
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integer or a string representing a channel layout. The default value
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of @var{channel_layout} is 3, which corresponds to CH_LAYOUT_STEREO.
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Check the channel_layout_map definition in
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@file{libavcodec/audioconvert.c} for the mapping between strings and
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channel layout values.
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Follow some examples:
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@example
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#  set the sample rate to 48000 Hz and the channel layout to CH_LAYOUT_MONO.
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anullsrc=48000:4
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# same as
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anullsrc=48000:mono
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@end example
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@c man end AUDIO SOURCES
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@chapter Audio Sinks
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@c man begin AUDIO SINKS
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Below is a description of the currently available audio sinks.
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@section anullsink
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Null audio sink, do absolutely nothing with the input audio. It is
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mainly useful as a template and to be employed in analysis / debugging
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tools.
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@c man end AUDIO SINKS
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@chapter Video Filters
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@c man begin VIDEO FILTERS
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When you configure your FFmpeg build, you can disable any of the
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existing filters using --disable-filters.
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The configure output will show the video filters included in your
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build.
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Below is a description of the currently available video filters.
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@section blackframe
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Detect frames that are (almost) completely black. Can be useful to
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detect chapter transitions or commercials. Output lines consist of
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the frame number of the detected frame, the percentage of blackness,
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the position in the file if known or -1 and the timestamp in seconds.
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In order to display the output lines, you need to set the loglevel at
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least to the AV_LOG_INFO value.
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The filter accepts the syntax:
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@example
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blackframe[=@var{amount}:[@var{threshold}]]
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@end example
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@var{amount} is the percentage of the pixels that have to be below the
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threshold, and defaults to 98.
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@var{threshold} is the threshold below which a pixel value is
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considered black, and defaults to 32.
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@section copy
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Copy the input source unchanged to the output. Mainly useful for
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testing purposes.
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@section crop
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Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}.
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The parameters are expressions containing the following constants:
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@table @option
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@item E, PI, PHI
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the corresponding mathematical approximated values for e
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(euler number), pi (greek PI), PHI (golden ratio)
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@item x, y
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the computed values for @var{x} and @var{y}. They are evaluated for
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each new frame.
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@item in_w, in_h
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the input width and heigth
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@item iw, ih
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same as @var{in_w} and @var{in_h}
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@item out_w, out_h
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the output (cropped) width and heigth
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@item ow, oh
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same as @var{out_w} and @var{out_h}
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@item n
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the number of input frame, starting from 0
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@item pos
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the position in the file of the input frame, NAN if unknown
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@item t
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timestamp expressed in seconds, NAN if the input timestamp is unknown
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@end table
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The @var{out_w} and @var{out_h} parameters specify the expressions for
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the width and height of the output (cropped) video. They are
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evaluated just at the configuration of the filter.
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The default value of @var{out_w} is "in_w", and the default value of
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@var{out_h} is "in_h".
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The expression for @var{out_w} may depend on the value of @var{out_h},
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and the expression for @var{out_h} may depend on @var{out_w}, but they
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cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
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evaluated after @var{out_w} and @var{out_h}.
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The @var{x} and @var{y} parameters specify the expressions for the
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position of the top-left corner of the output (non-cropped) area. They
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are evaluated for each frame. If the evaluated value is not valid, it
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is approximated to the nearest valid value.
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The default value of @var{x} is "(in_w-out_w)/2", and the default
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value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
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the center of the input image.
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The expression for @var{x} may depend on @var{y}, and the expression
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for @var{y} may depend on @var{x}.
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Follow some examples:
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@example
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# crop the central input area with size 100x100
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crop=100:100
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# crop the central input area with size 2/3 of the input video
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"crop=2/3*in_w:2/3*in_h"
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# crop the input video central square
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crop=in_h
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# delimit the rectangle with the top-left corner placed at position
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# 100:100 and the right-bottom corner corresponding to the right-bottom
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# corner of the input image.
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crop=in_w-100:in_h-100:100:100
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# crop 10 pixels from the left and right borders, and 20 pixels from
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# the top and bottom borders
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"crop=in_w-2*10:in_h-2*20"
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# keep only the bottom right quarter of the input image
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"crop=in_w/2:in_h/2:in_w/2:in_h/2"
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# crop height for getting Greek harmony
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"crop=in_w:1/PHI*in_w"
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# trembling effect
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"crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)"
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# erratic camera effect depending on timestamp
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"crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
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# set x depending on the value of y
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"crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
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@end example
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@section cropdetect
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Auto-detect crop size.
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Calculate necessary cropping parameters and prints the recommended
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parameters through the logging system. The detected dimensions
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correspond to the non-black area of the input video.
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It accepts the syntax:
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@example
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cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]
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@end example
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@table @option
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@item limit
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Threshold, which can be optionally specified from nothing (0) to
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everything (255), defaults to 24.
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@item round
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Value which the width/height should be divisible by, defaults to
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16. The offset is automatically adjusted to center the video. Use 2 to
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get only even dimensions (needed for 4:2:2 video). 16 is best when
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encoding to most video codecs.
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@item reset
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Counter that determines after how many frames cropdetect will reset
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the previously detected largest video area and start over to detect
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the current optimal crop area. Defaults to 0.
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This can be useful when channel logos distort the video area. 0
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indicates never reset and return the largest area encountered during
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playback.
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@end table
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@section drawbox
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Draw a colored box on the input image.
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It accepts the syntax:
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@example
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drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}
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@end example
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@table @option
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@item x, y
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Specify the top left corner coordinates of the box. Default to 0.
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@item width, height
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Specify the width and height of the box, if 0 they are interpreted as
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the input width and height. Default to 0.
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@item color
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Specify the color of the box to write, it can be the name of a color
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(case insensitive match) or a 0xRRGGBB[AA] sequence.
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@end table
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Follow some examples:
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@example
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# draw a black box around the edge of the input image
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drawbox
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# draw a box with color red and an opacity of 50%
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drawbox=10:20:200:60:red@@0.5"
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@end example
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@section drawtext
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Draw text string or text from specified file on top of video using the
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libfreetype library.
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To enable compilation of this filter you need to configure FFmpeg with
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@code{--enable-libfreetype}.
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The filter also recognizes strftime() sequences in the provided text
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and expands them accordingly. Check the documentation of strftime().
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The filter accepts parameters as a list of @var{key}=@var{value} pairs,
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separated by ":".
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The description of the accepted parameters follows.
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@table @option
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@item fontfile
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The font file to be used for drawing text. Path must be included.
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This parameter is mandatory.
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@item text
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The text string to be drawn. The text must be a sequence of UTF-8
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encoded characters.
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This parameter is mandatory if no file is specified with the parameter
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@var{textfile}.
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@item textfile
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A text file containing text to be drawn. The text must be a sequence
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of UTF-8 encoded characters.
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This parameter is mandatory if no text string is specified with the
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parameter @var{text}.
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If both text and textfile are specified, an error is thrown.
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@item x, y
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The offsets where text will be drawn within the video frame.
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Relative to the top/left border of the output image.
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The default value of @var{x} and @var{y} is 0.
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@item fontsize
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The font size to be used for drawing text.
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The default value of @var{fontsize} is 16.
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@item fontcolor
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The color to be used for drawing fonts.
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Either a string (e.g. "red") or in 0xRRGGBB[AA] format
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(e.g. "0xff000033"), possibly followed by an alpha specifier.
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The default value of @var{fontcolor} is "black".
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@item boxcolor
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The color to be used for drawing box around text.
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Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
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(e.g. "0xff00ff"), possibly followed by an alpha specifier.
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The default value of @var{boxcolor} is "white".
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@item box
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Used to draw a box around text using background color.
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Value should be either 1 (enable) or 0 (disable).
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The default value of @var{box} is 0.
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@item shadowx, shadowy
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The x and y offsets for the text shadow position with respect to the
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position of the text. They can be either positive or negative
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values. Default value for both is "0".
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@item shadowcolor
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The color to be used for drawing a shadow behind the drawn text.  It
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can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
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form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
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The default value of @var{shadowcolor} is "black".
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@item ft_load_flags
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Flags to be used for loading the fonts.
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The flags map the corresponding flags supported by libfreetype, and are
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a combination of the following values:
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@table @var
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@item default
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@item no_scale
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@item no_hinting
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@item render
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@item no_bitmap
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@item vertical_layout
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@item force_autohint
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@item crop_bitmap
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@item pedantic
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@item ignore_global_advance_width
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@item no_recurse
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@item ignore_transform
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@item monochrome
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@item linear_design
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@item no_autohint
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@item end table
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@end table
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Default value is "render".
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For more information consult the documentation for the FT_LOAD_*
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libfreetype flags.
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@item tabsize
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The size in number of spaces to use for rendering the tab.
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Default value is 4.
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@end table
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For example the command:
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@example
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drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
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@end example
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will draw "Test Text" with font FreeSerif, using the default values
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for the optional parameters.
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The command:
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@example
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drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
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          x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
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@end example
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will draw 'Test Text' with font FreeSerif of size 24 at position x=100
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and y=50 (counting from the top-left corner of the screen), text is
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yellow with a red box around it. Both the text and the box have an
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opacity of 20%.
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Note that the double quotes are not necessary if spaces are not used
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within the parameter list.
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For more information about libfreetype, check:
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@url{http://www.freetype.org/}.
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@section fade
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Apply fade-in/out effect to input video.
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It accepts the parameters:
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@var{type}:@var{start_frame}:@var{nb_frames}
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@var{type} specifies if the effect type, can be either "in" for
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fade-in, or "out" for a fade-out effect.
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@var{start_frame} specifies the number of the start frame for starting
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to apply the fade effect.
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@var{nb_frames} specifies the number of frames for which the fade
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effect has to last. At the end of the fade-in effect the output video
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will have the same intensity as the input video, at the end of the
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fade-out transition the output video will be completely black.
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A few usage examples follow, usable too as test scenarios.
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@example
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# fade in first 30 frames of video
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fade=in:0:30
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# fade out last 45 frames of a 200-frame video
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fade=out:155:45
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# fade in first 25 frames and fade out last 25 frames of a 1000-frame video
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fade=in:0:25, fade=out:975:25
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# make first 5 frames black, then fade in from frame 5-24
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fade=in:5:20
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@end example
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@section fieldorder
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Transform the field order of the input video.
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It accepts one parameter which specifies the required field order that
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the input interlaced video will be transformed to. The parameter can
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assume one of the following values:
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@table @option
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@item 0 or bff
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output bottom field first
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@item 1 or tff
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output top field first
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@end table
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Default value is "tff".
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Transformation is achieved by shifting the picture content up or down
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by one line, and filling the remaining line with appropriate picture content.
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This method is consistent with most broadcast field order converters.
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If the input video is not flagged as being interlaced, or it is already
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flagged as being of the required output field order then this filter does
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not alter the incoming video.
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This filter is very useful when converting to or from PAL DV material,
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which is bottom field first.
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For example:
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@example
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./ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
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@end example
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@section fifo
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Buffer input images and send them when they are requested.
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This filter is mainly useful when auto-inserted by the libavfilter
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framework.
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The filter does not take parameters.
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@section format
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Convert the input video to one of the specified pixel formats.
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Libavfilter will try to pick one that is supported for the input to
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the next filter.
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The filter accepts a list of pixel format names, separated by ":",
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for example "yuv420p:monow:rgb24".
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Some examples follow:
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@example
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# convert the input video to the format "yuv420p"
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format=yuv420p
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# convert the input video to any of the formats in the list
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format=yuv420p:yuv444p:yuv410p
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@end example
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@anchor{frei0r}
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@section frei0r
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Apply a frei0r effect to the input video.
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To enable compilation of this filter you need to install the frei0r
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header and configure FFmpeg with --enable-frei0r.
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The filter supports the syntax:
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@example
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@var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]
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@end example
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@var{filter_name} is the name to the frei0r effect to load. If the
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environment variable @env{FREI0R_PATH} is defined, the frei0r effect
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is searched in each one of the directories specified by the colon
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separated list in @env{FREIOR_PATH}, otherwise in the standard frei0r
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paths, which are in this order: @file{HOME/.frei0r-1/lib/},
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@file{/usr/local/lib/frei0r-1/}, @file{/usr/lib/frei0r-1/}.
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@var{param1}, @var{param2}, ... , @var{paramN} specify the parameters
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for the frei0r effect.
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A frei0r effect parameter can be a boolean (whose values are specified
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with "y" and "n"), a double, a color (specified by the syntax
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@var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
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numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
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description), a position (specified by the syntax @var{X}/@var{Y},
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@var{X} and @var{Y} being float numbers) and a string.
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613
The number and kind of parameters depend on the loaded effect. If an
614
effect parameter is not specified the default value is set.
615

    
616
Some examples follow:
617
@example
618
# apply the distort0r effect, set the first two double parameters
619
frei0r=distort0r:0.5:0.01
620

    
621
# apply the colordistance effect, takes a color as first parameter
622
frei0r=colordistance:0.2/0.3/0.4
623
frei0r=colordistance:violet
624
frei0r=colordistance:0x112233
625

    
626
# apply the perspective effect, specify the top left and top right
627
# image positions
628
frei0r=perspective:0.2/0.2:0.8/0.2
629
@end example
630

    
631
For more information see:
632
@url{http://piksel.org/frei0r}
633

    
634
@section gradfun
635

    
636
Fix the banding artifacts that are sometimes introduced into nearly flat
637
regions by truncation to 8bit colordepth.
638
Interpolate the gradients that should go where the bands are, and
639
dither them.
640

    
641
This filter is designed for playback only.  Do not use it prior to
642
lossy compression, because compression tends to lose the dither and
643
bring back the bands.
644

    
645
The filter takes two optional parameters, separated by ':':
646
@var{strength}:@var{radius}
647

    
648
@var{strength} is the maximum amount by which the filter will change
649
any one pixel. Also the threshold for detecting nearly flat
650
regions. Acceptable values range from .51 to 255, default value is
651
1.2, out-of-range values will be clipped to the valid range.
652

    
653
@var{radius} is the neighborhood to fit the gradient to. A larger
654
radius makes for smoother gradients, but also prevents the filter from
655
modifying the pixels near detailed regions. Acceptable values are
656
8-32, default value is 16, out-of-range values will be clipped to the
657
valid range.
658

    
659
@example
660
# default parameters
661
gradfun=1.2:16
662

    
663
# omitting radius
664
gradfun=1.2
665
@end example
666

    
667
@section hflip
668

    
669
Flip the input video horizontally.
670

    
671
For example to horizontally flip the video in input with
672
@file{ffmpeg}:
673
@example
674
ffmpeg -i in.avi -vf "hflip" out.avi
675
@end example
676

    
677
@section hqdn3d
678

    
679
High precision/quality 3d denoise filter. This filter aims to reduce
680
image noise producing smooth images and making still images really
681
still. It should enhance compressibility.
682

    
683
It accepts the following optional parameters:
684
@var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
685

    
686
@table @option
687
@item luma_spatial
688
a non-negative float number which specifies spatial luma strength,
689
defaults to 4.0
690

    
691
@item chroma_spatial
692
a non-negative float number which specifies spatial chroma strength,
693
defaults to 3.0*@var{luma_spatial}/4.0
694

    
695
@item luma_tmp
696
a float number which specifies luma temporal strength, defaults to
697
6.0*@var{luma_spatial}/4.0
698

    
699
@item chroma_tmp
700
a float number which specifies chroma temporal strength, defaults to
701
@var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
702
@end table
703

    
704
@section mp
705

    
706
Apply an MPlayer filter to the input video.
707

    
708
This filter provides a wrapper around most of the filters of
709
MPlayer/MEncoder.
710

    
711
This wrapper is considered experimental. Some of the wrapped filters
712
may not work properly and we may drop support for them, as they will
713
be implemented natively into FFmpeg. Thus you should avoid
714
depending on them when writing portable scripts.
715

    
716
The filters accepts the parameters:
717
@var{filter_name}[:=]@var{filter_params}
718

    
719
@var{filter_name} is the name of a supported MPlayer filter,
720
@var{filter_params} is a string containing the parameters accepted by
721
the named filter.
722

    
723
The list of the currently supported filters follows:
724
@table @var
725
@item 2xsai
726
@item blackframe
727
@item boxblur
728
@item cropdetect
729
@item decimate
730
@item delogo
731
@item denoise3d
732
@item detc
733
@item dint
734
@item divtc
735
@item down3dright
736
@item dsize
737
@item eq2
738
@item eq
739
@item field
740
@item fil
741
@item fixpts
742
@item framestep
743
@item fspp
744
@item geq
745
@item gradfun
746
@item harddup
747
@item hqdn3d
748
@item hue
749
@item il
750
@item ilpack
751
@item ivtc
752
@item kerndeint
753
@item mcdeint
754
@item mirror
755
@item noise
756
@item ow
757
@item palette
758
@item perspective
759
@item phase
760
@item pp7
761
@item pullup
762
@item qp
763
@item rectangle
764
@item remove_logo
765
@item rgbtest
766
@item rotate
767
@item sab
768
@item screenshot
769
@item smartblur
770
@item softpulldown
771
@item softskip
772
@item spp
773
@item swapuv
774
@item telecine
775
@item test
776
@item tile
777
@item tinterlace
778
@item unsharp
779
@item uspp
780
@item yuvcsp
781
@item yvu9
782
@end table
783

    
784
The parameter syntax and behavior for the listed filters are the same
785
of the corresponding MPlayer filters. For detailed instructions check
786
the "VIDEO FILTERS" section in the MPlayer manual.
787

    
788
Some examples follow:
789
@example
790
# remove a logo by interpolating the surrounding pixels
791
mp=delogo=200:200:80:20:1
792

    
793
# adjust gamma, brightness, contrast
794
mp=eq2=1.0:2:0.5
795

    
796
# tweak hue and saturation
797
mp=hue=100:-10
798
@end example
799

    
800
See also mplayer(1), @url{http://www.mplayerhq.hu/}.
801

    
802
@section noformat
803

    
804
Force libavfilter not to use any of the specified pixel formats for the
805
input to the next filter.
806

    
807
The filter accepts a list of pixel format names, separated by ":",
808
for example "yuv420p:monow:rgb24".
809

    
810
Some examples follow:
811
@example
812
# force libavfilter to use a format different from "yuv420p" for the
813
# input to the vflip filter
814
noformat=yuv420p,vflip
815

    
816
# convert the input video to any of the formats not contained in the list
817
noformat=yuv420p:yuv444p:yuv410p
818
@end example
819

    
820
@section null
821

    
822
Pass the video source unchanged to the output.
823

    
824
@section ocv
825

    
826
Apply video transform using libopencv.
827

    
828
To enable this filter install libopencv library and headers and
829
configure FFmpeg with --enable-libopencv.
830

    
831
The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
832

    
833
@var{filter_name} is the name of the libopencv filter to apply.
834

    
835
@var{filter_params} specifies the parameters to pass to the libopencv
836
filter. If not specified the default values are assumed.
837

    
838
Refer to the official libopencv documentation for more precise
839
informations:
840
@url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
841

    
842
Follows the list of supported libopencv filters.
843

    
844
@anchor{dilate}
845
@subsection dilate
846

    
847
Dilate an image by using a specific structuring element.
848
This filter corresponds to the libopencv function @code{cvDilate}.
849

    
850
It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
851

    
852
@var{struct_el} represents a structuring element, and has the syntax:
853
@var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
854

    
855
@var{cols} and @var{rows} represent the number of colums and rows of
856
the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
857
point, and @var{shape} the shape for the structuring element, and
858
can be one of the values "rect", "cross", "ellipse", "custom".
859

    
860
If the value for @var{shape} is "custom", it must be followed by a
861
string of the form "=@var{filename}". The file with name
862
@var{filename} is assumed to represent a binary image, with each
863
printable character corresponding to a bright pixel. When a custom
864
@var{shape} is used, @var{cols} and @var{rows} are ignored, the number
865
or columns and rows of the read file are assumed instead.
866

    
867
The default value for @var{struct_el} is "3x3+0x0/rect".
868

    
869
@var{nb_iterations} specifies the number of times the transform is
870
applied to the image, and defaults to 1.
871

    
872
Follow some example:
873
@example
874
# use the default values
875
ocv=dilate
876

    
877
# dilate using a structuring element with a 5x5 cross, iterate two times
878
ocv=dilate=5x5+2x2/cross:2
879

    
880
# read the shape from the file diamond.shape, iterate two times
881
# the file diamond.shape may contain a pattern of characters like this:
882
#   *
883
#  ***
884
# *****
885
#  ***
886
#   *
887
# the specified cols and rows are ignored (but not the anchor point coordinates)
888
ocv=0x0+2x2/custom=diamond.shape:2
889
@end example
890

    
891
@subsection erode
892

    
893
Erode an image by using a specific structuring element.
894
This filter corresponds to the libopencv function @code{cvErode}.
895

    
896
The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
897
with the same meaning and use of those of the dilate filter
898
(@pxref{dilate}).
899

    
900
@subsection smooth
901

    
902
Smooth the input video.
903

    
904
The filter takes the following parameters:
905
@var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
906

    
907
@var{type} is the type of smooth filter to apply, and can be one of
908
the following values: "blur", "blur_no_scale", "median", "gaussian",
909
"bilateral". The default value is "gaussian".
910

    
911
@var{param1}, @var{param2}, @var{param3}, and @var{param4} are
912
parameters whose meanings depend on smooth type. @var{param1} and
913
@var{param2} accept integer positive values or 0, @var{param3} and
914
@var{param4} accept float values.
915

    
916
The default value for @var{param1} is 3, the default value for the
917
other parameters is 0.
918

    
919
These parameters correspond to the parameters assigned to the
920
libopencv function @code{cvSmooth}.
921

    
922
@section overlay
923

    
924
Overlay one video on top of another.
925

    
926
It takes two inputs and one output, the first input is the "main"
927
video on which the second input is overlayed.
928

    
929
It accepts the parameters: @var{x}:@var{y}.
930

    
931
@var{x} is the x coordinate of the overlayed video on the main video,
932
@var{y} is the y coordinate. The parameters are expressions containing
933
the following parameters:
934

    
935
@table @option
936
@item main_w, main_h
937
main input width and height
938

    
939
@item W, H
940
same as @var{main_w} and @var{main_h}
941

    
942
@item overlay_w, overlay_h
943
overlay input width and height
944

    
945
@item w, h
946
same as @var{overlay_w} and @var{overlay_h}
947
@end table
948

    
949
Be aware that frames are taken from each input video in timestamp
950
order, hence, if their initial timestamps differ, it is a a good idea
951
to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
952
have them begin in the same zero timestamp, as it does the example for
953
the @var{movie} filter.
954

    
955
Follow some examples:
956
@example
957
# draw the overlay at 10 pixels from the bottom right
958
# corner of the main video.
959
overlay=main_w-overlay_w-10:main_h-overlay_h-10
960

    
961
# insert a transparent PNG logo in the bottom left corner of the input
962
movie=logo.png [logo];
963
[in][logo] overlay=10:main_h-overlay_h-10 [out]
964

    
965
# insert 2 different transparent PNG logos (second logo on bottom
966
# right corner):
967
movie=logo1.png [logo1];
968
movie=logo2.png [logo2];
969
[in][logo1]       overlay=10:H-h-10 [in+logo1];
970
[in+logo1][logo2] overlay=W-w-10:H-h-10 [out]
971

    
972
# add a transparent color layer on top of the main video,
973
# WxH specifies the size of the main input to the overlay filter
974
color=red@.3:WxH [over]; [in][over] overlay [out]
975
@end example
976

    
977
You can chain togheter more overlays but the efficiency of such
978
approach is yet to be tested.
979

    
980
@section pad
981

    
982
Add paddings to the input image, and places the original input at the
983
given coordinates @var{x}, @var{y}.
984

    
985
It accepts the following parameters:
986
@var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
987

    
988
The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
989
expressions containing the following constants:
990

    
991
@table @option
992
@item E, PI, PHI
993
the corresponding mathematical approximated values for e
994
(euler number), pi (greek PI), phi (golden ratio)
995

    
996
@item in_w, in_h
997
the input video width and heigth
998

    
999
@item iw, ih
1000
same as @var{in_w} and @var{in_h}
1001

    
1002
@item out_w, out_h
1003
the output width and heigth, that is the size of the padded area as
1004
specified by the @var{width} and @var{height} expressions
1005

    
1006
@item ow, oh
1007
same as @var{out_w} and @var{out_h}
1008

    
1009
@item x, y
1010
x and y offsets as specified by the @var{x} and @var{y}
1011
expressions, or NAN if not yet specified
1012

    
1013
@item a
1014
input display aspect ratio, same as @var{iw} / @var{ih}
1015

    
1016
@item hsub, vsub
1017
horizontal and vertical chroma subsample values. For example for the
1018
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1019
@end table
1020

    
1021
Follows the description of the accepted parameters.
1022

    
1023
@table @option
1024
@item width, height
1025

    
1026
Specify the size of the output image with the paddings added. If the
1027
value for @var{width} or @var{height} is 0, the corresponding input size
1028
is used for the output.
1029

    
1030
The @var{width} expression can reference the value set by the
1031
@var{height} expression, and viceversa.
1032

    
1033
The default value of @var{width} and @var{height} is 0.
1034

    
1035
@item x, y
1036

    
1037
Specify the offsets where to place the input image in the padded area
1038
with respect to the top/left border of the output image.
1039

    
1040
The @var{x} expression can reference the value set by the @var{y}
1041
expression, and viceversa.
1042

    
1043
The default value of @var{x} and @var{y} is 0.
1044

    
1045
@item color
1046

    
1047
Specify the color of the padded area, it can be the name of a color
1048
(case insensitive match) or a 0xRRGGBB[AA] sequence.
1049

    
1050
The default value of @var{color} is "black".
1051

    
1052
@end table
1053

    
1054
Some examples follow:
1055

    
1056
@example
1057
# Add paddings with color "violet" to the input video. Output video
1058
# size is 640x480, the top-left corner of the input video is placed at
1059
# column 0, row 40.
1060
pad=640:480:0:40:violet
1061

    
1062
# pad the input to get an output with dimensions increased bt 3/2,
1063
# and put the input video at the center of the padded area
1064
pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
1065

    
1066
# pad the input to get a squared output with size equal to the maximum
1067
# value between the input width and height, and put the input video at
1068
# the center of the padded area
1069
pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
1070

    
1071
# pad the input to get a final w/h ratio of 16:9
1072
pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
1073

    
1074
# double output size and put the input video in the bottom-right
1075
# corner of the output padded area
1076
pad="2*iw:2*ih:ow-iw:oh-ih"
1077
@end example
1078

    
1079
@section pixdesctest
1080

    
1081
Pixel format descriptor test filter, mainly useful for internal
1082
testing. The output video should be equal to the input video.
1083

    
1084
For example:
1085
@example
1086
format=monow, pixdesctest
1087
@end example
1088

    
1089
can be used to test the monowhite pixel format descriptor definition.
1090

    
1091
@section scale
1092

    
1093
Scale the input video to @var{width}:@var{height} and/or convert the image format.
1094

    
1095
The parameters @var{width} and @var{height} are expressions containing
1096
the following constants:
1097

    
1098
@table @option
1099
@item E, PI, PHI
1100
the corresponding mathematical approximated values for e
1101
(euler number), pi (greek PI), phi (golden ratio)
1102

    
1103
@item in_w, in_h
1104
the input width and heigth
1105

    
1106
@item iw, ih
1107
same as @var{in_w} and @var{in_h}
1108

    
1109
@item out_w, out_h
1110
the output (cropped) width and heigth
1111

    
1112
@item ow, oh
1113
same as @var{out_w} and @var{out_h}
1114

    
1115
@item a
1116
input display aspect ratio, same as @var{iw} / @var{ih}
1117

    
1118
@item hsub, vsub
1119
horizontal and vertical chroma subsample values. For example for the
1120
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1121
@end table
1122

    
1123
If the input image format is different from the format requested by
1124
the next filter, the scale filter will convert the input to the
1125
requested format.
1126

    
1127
If the value for @var{width} or @var{height} is 0, the respective input
1128
size is used for the output.
1129

    
1130
If the value for @var{width} or @var{height} is -1, the scale filter will
1131
use, for the respective output size, a value that maintains the aspect
1132
ratio of the input image.
1133

    
1134
The default value of @var{width} and @var{height} is 0.
1135

    
1136
Some examples follow:
1137
@example
1138
# scale the input video to a size of 200x100.
1139
scale=200:100
1140

    
1141
# scale the input to 2x
1142
scale=2*iw:2*ih
1143
# the above is the same as
1144
scale=2*in_w:2*in_h
1145

    
1146
# scale the input to half size
1147
scale=iw/2:ih/2
1148

    
1149
# increase the width, and set the height to the same size
1150
scale=3/2*iw:ow
1151

    
1152
# seek for Greek harmony
1153
scale=iw:1/PHI*iw
1154
scale=ih*PHI:ih
1155

    
1156
# increase the height, and set the width to 3/2 of the height
1157
scale=3/2*oh:3/5*ih
1158

    
1159
# increase the size, but make the size a multiple of the chroma
1160
scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
1161

    
1162
# increase the width to a maximum of 500 pixels, keep the same input aspect ratio
1163
scale='min(500\, iw*3/2):-1'
1164
@end example
1165

    
1166
@anchor{setdar}
1167
@section setdar
1168

    
1169
Set the Display Aspect Ratio for the filter output video.
1170

    
1171
This is done by changing the specified Sample (aka Pixel) Aspect
1172
Ratio, according to the following equation:
1173
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
1174

    
1175
Keep in mind that this filter does not modify the pixel dimensions of
1176
the video frame. Also the display aspect ratio set by this filter may
1177
be changed by later filters in the filterchain, e.g. in case of
1178
scaling or if another "setdar" or a "setsar" filter is applied.
1179

    
1180
The filter accepts a parameter string which represents the wanted
1181
display aspect ratio.
1182
The parameter can be a floating point number string, or an expression
1183
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
1184
numerator and denominator of the aspect ratio.
1185
If the parameter is not specified, it is assumed the value "0:1".
1186

    
1187
For example to change the display aspect ratio to 16:9, specify:
1188
@example
1189
setdar=16:9
1190
# the above is equivalent to
1191
setdar=1.77777
1192
@end example
1193

    
1194
See also the "setsar" filter documentation (@pxref{setsar}).
1195

    
1196
@section setpts
1197

    
1198
Change the PTS (presentation timestamp) of the input video frames.
1199

    
1200
Accept in input an expression evaluated through the eval API, which
1201
can contain the following constants:
1202

    
1203
@table @option
1204
@item PTS
1205
the presentation timestamp in input
1206

    
1207
@item PI
1208
Greek PI
1209

    
1210
@item PHI
1211
golden ratio
1212

    
1213
@item E
1214
Euler number
1215

    
1216
@item N
1217
the count of the input frame, starting from 0.
1218

    
1219
@item STARTPTS
1220
the PTS of the first video frame
1221

    
1222
@item INTERLACED
1223
tell if the current frame is interlaced
1224

    
1225
@item POS
1226
original position in the file of the frame, or undefined if undefined
1227
for the current frame
1228

    
1229
@item PREV_INPTS
1230
previous input PTS
1231

    
1232
@item PREV_OUTPTS
1233
previous output PTS
1234

    
1235
@end table
1236

    
1237
Some examples follow:
1238

    
1239
@example
1240
# start counting PTS from zero
1241
setpts=PTS-STARTPTS
1242

    
1243
# fast motion
1244
setpts=0.5*PTS
1245

    
1246
# slow motion
1247
setpts=2.0*PTS
1248

    
1249
# fixed rate 25 fps
1250
setpts=N/(25*TB)
1251

    
1252
# fixed rate 25 fps with some jitter
1253
setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
1254
@end example
1255

    
1256
@anchor{setsar}
1257
@section setsar
1258

    
1259
Set the Sample (aka Pixel) Aspect Ratio for the filter output video.
1260

    
1261
Note that as a consequence of the application of this filter, the
1262
output display aspect ratio will change according to the following
1263
equation:
1264
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
1265

    
1266
Keep in mind that the sample aspect ratio set by this filter may be
1267
changed by later filters in the filterchain, e.g. if another "setsar"
1268
or a "setdar" filter is applied.
1269

    
1270
The filter accepts a parameter string which represents the wanted
1271
sample aspect ratio.
1272
The parameter can be a floating point number string, or an expression
1273
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
1274
numerator and denominator of the aspect ratio.
1275
If the parameter is not specified, it is assumed the value "0:1".
1276

    
1277
For example to change the sample aspect ratio to 10:11, specify:
1278
@example
1279
setsar=10:11
1280
@end example
1281

    
1282
@section settb
1283

    
1284
Set the timebase to use for the output frames timestamps.
1285
It is mainly useful for testing timebase configuration.
1286

    
1287
It accepts in input an arithmetic expression representing a rational.
1288
The expression can contain the constants "PI", "E", "PHI", "AVTB" (the
1289
default timebase), and "intb" (the input timebase).
1290

    
1291
The default value for the input is "intb".
1292

    
1293
Follow some examples.
1294

    
1295
@example
1296
# set the timebase to 1/25
1297
settb=1/25
1298

    
1299
# set the timebase to 1/10
1300
settb=0.1
1301

    
1302
#set the timebase to 1001/1000
1303
settb=1+0.001
1304

    
1305
#set the timebase to 2*intb
1306
settb=2*intb
1307

    
1308
#set the default timebase value
1309
settb=AVTB
1310
@end example
1311

    
1312
@section slicify
1313

    
1314
Pass the images of input video on to next video filter as multiple
1315
slices.
1316

    
1317
@example
1318
./ffmpeg -i in.avi -vf "slicify=32" out.avi
1319
@end example
1320

    
1321
The filter accepts the slice height as parameter. If the parameter is
1322
not specified it will use the default value of 16.
1323

    
1324
Adding this in the beginning of filter chains should make filtering
1325
faster due to better use of the memory cache.
1326

    
1327
@section transpose
1328

    
1329
Transpose rows with columns in the input video and optionally flip it.
1330

    
1331
It accepts a parameter representing an integer, which can assume the
1332
values:
1333

    
1334
@table @samp
1335
@item 0
1336
Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
1337
@example
1338
L.R     L.l
1339
. . ->  . .
1340
l.r     R.r
1341
@end example
1342

    
1343
@item 1
1344
Rotate by 90 degrees clockwise, that is:
1345
@example
1346
L.R     l.L
1347
. . ->  . .
1348
l.r     r.R
1349
@end example
1350

    
1351
@item 2
1352
Rotate by 90 degrees counterclockwise, that is:
1353
@example
1354
L.R     R.r
1355
. . ->  . .
1356
l.r     L.l
1357
@end example
1358

    
1359
@item 3
1360
Rotate by 90 degrees clockwise and vertically flip, that is:
1361
@example
1362
L.R     r.R
1363
. . ->  . .
1364
l.r     l.L
1365
@end example
1366
@end table
1367

    
1368
@section unsharp
1369

    
1370
Sharpen or blur the input video.
1371

    
1372
It accepts the following parameters:
1373
@var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
1374

    
1375
Negative values for the amount will blur the input video, while positive
1376
values will sharpen. All parameters are optional and default to the
1377
equivalent of the string '5:5:1.0:0:0:0.0'.
1378

    
1379
@table @option
1380

    
1381
@item luma_msize_x
1382
Set the luma matrix horizontal size. It can be an integer between 3
1383
and 13, default value is 5.
1384

    
1385
@item luma_msize_y
1386
Set the luma matrix vertical size. It can be an integer between 3
1387
and 13, default value is 5.
1388

    
1389
@item luma_amount
1390
Set the luma effect strength. It can be a float number between -2.0
1391
and 5.0, default value is 1.0.
1392

    
1393
@item chroma_msize_x
1394
Set the chroma matrix horizontal size. It can be an integer between 3
1395
and 13, default value is 0.
1396

    
1397
@item chroma_msize_y
1398
Set the chroma matrix vertical size. It can be an integer between 3
1399
and 13, default value is 0.
1400

    
1401
@item luma_amount
1402
Set the chroma effect strength. It can be a float number between -2.0
1403
and 5.0, default value is 0.0.
1404

    
1405
@end table
1406

    
1407
@example
1408
# Strong luma sharpen effect parameters
1409
unsharp=7:7:2.5
1410

    
1411
# Strong blur of both luma and chroma parameters
1412
unsharp=7:7:-2:7:7:-2
1413

    
1414
# Use the default values with @command{ffmpeg}
1415
./ffmpeg -i in.avi -vf "unsharp" out.mp4
1416
@end example
1417

    
1418
@section vflip
1419

    
1420
Flip the input video vertically.
1421

    
1422
@example
1423
./ffmpeg -i in.avi -vf "vflip" out.avi
1424
@end example
1425

    
1426
@section yadif
1427

    
1428
Deinterlace the input video ("yadif" means "yet another deinterlacing
1429
filter").
1430

    
1431
It accepts the optional parameters: @var{mode}:@var{parity}.
1432

    
1433
@var{mode} specifies the interlacing mode to adopt, accepts one of the
1434
following values:
1435

    
1436
@table @option
1437
@item 0
1438
output 1 frame for each frame
1439
@item 1
1440
output 1 frame for each field
1441
@item 2
1442
like 0 but skips spatial interlacing check
1443
@item 3
1444
like 1 but skips spatial interlacing check
1445
@end table
1446

    
1447
Default value is 0.
1448

    
1449
@var{parity} specifies the picture field parity assumed for the input
1450
interlaced video, accepts one of the following values:
1451

    
1452
@table @option
1453
@item 0
1454
assume bottom field first
1455
@item 1
1456
assume top field first
1457
@item -1
1458
enable automatic detection
1459
@end table
1460

    
1461
Default value is -1.
1462
If interlacing is unknown or decoder does not export this information,
1463
top field first will be assumed.
1464

    
1465
@c man end VIDEO FILTERS
1466

    
1467
@chapter Video Sources
1468
@c man begin VIDEO SOURCES
1469

    
1470
Below is a description of the currently available video sources.
1471

    
1472
@section buffer
1473

    
1474
Buffer video frames, and make them available to the filter chain.
1475

    
1476
This source is mainly intended for a programmatic use, in particular
1477
through the interface defined in @file{libavfilter/vsrc_buffer.h}.
1478

    
1479
It accepts the following parameters:
1480
@var{width}:@var{height}:@var{pix_fmt_string}:@var{timebase_num}:@var{timebase_den}:@var{sample_aspect_ratio_num}:@var{sample_aspect_ratio.den}
1481

    
1482
All the parameters need to be explicitely defined.
1483

    
1484
Follows the list of the accepted parameters.
1485

    
1486
@table @option
1487

    
1488
@item width, height
1489
Specify the width and height of the buffered video frames.
1490

    
1491
@item pix_fmt_string
1492
A string representing the pixel format of the buffered video frames.
1493
It may be a number corresponding to a pixel format, or a pixel format
1494
name.
1495

    
1496
@item timebase_num, timebase_den
1497
Specify numerator and denomitor of the timebase assumed by the
1498
timestamps of the buffered frames.
1499

    
1500
@item sample_aspect_ratio.num, sample_aspect_ratio.den
1501
Specify numerator and denominator of the sample aspect ratio assumed
1502
by the video frames.
1503
@end table
1504

    
1505
For example:
1506
@example
1507
buffer=320:240:yuv410p:1:24:1:1
1508
@end example
1509

    
1510
will instruct the source to accept video frames with size 320x240 and
1511
with format "yuv410p", assuming 1/24 as the timestamps timebase and
1512
square pixels (1:1 sample aspect ratio).
1513
Since the pixel format with name "yuv410p" corresponds to the number 6
1514
(check the enum PixelFormat definition in @file{libavutil/pixfmt.h}),
1515
this example corresponds to:
1516
@example
1517
buffer=320:240:6:1:24
1518
@end example
1519

    
1520
@section color
1521

    
1522
Provide an uniformly colored input.
1523

    
1524
It accepts the following parameters:
1525
@var{color}:@var{frame_size}:@var{frame_rate}
1526

    
1527
Follows the description of the accepted parameters.
1528

    
1529
@table @option
1530

    
1531
@item color
1532
Specify the color of the source. It can be the name of a color (case
1533
insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an
1534
alpha specifier. The default value is "black".
1535

    
1536
@item frame_size
1537
Specify the size of the sourced video, it may be a string of the form
1538
@var{width}x@var{heigth}, or the name of a size abbreviation. The
1539
default value is "320x240".
1540

    
1541
@item frame_rate
1542
Specify the frame rate of the sourced video, as the number of frames
1543
generated per second. It has to be a string in the format
1544
@var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
1545
number or a valid video frame rate abbreviation. The default value is
1546
"25".
1547

    
1548
@end table
1549

    
1550
For example the following graph description will generate a red source
1551
with an opacity of 0.2, with size "qcif" and a frame rate of 10
1552
frames per second, which will be overlayed over the source connected
1553
to the pad with identifier "in".
1554

    
1555
@example
1556
"color=red@@0.2:qcif:10 [color]; [in][color] overlay [out]"
1557
@end example
1558

    
1559
@section movie
1560

    
1561
Read a video stream from a movie container.
1562

    
1563
It accepts the syntax: @var{movie_name}[:@var{options}] where
1564
@var{movie_name} is the name of the resource to read (not necessarily
1565
a file but also a device or a stream accessed through some protocol),
1566
and @var{options} is an optional sequence of @var{key}=@var{value}
1567
pairs, separated by ":".
1568

    
1569
The description of the accepted options follows.
1570

    
1571
@table @option
1572

    
1573
@item format_name, f
1574
Specifies the format assumed for the movie to read, and can be either
1575
the name of a container or an input device. If not specified the
1576
format is guessed from @var{movie_name} or by probing.
1577

    
1578
@item seek_point, sp
1579
Specifies the seek point in seconds, the frames will be output
1580
starting from this seek point, the parameter is evaluated with
1581
@code{av_strtod} so the numerical value may be suffixed by an IS
1582
postfix. Default value is "0".
1583

    
1584
@item stream_index, si
1585
Specifies the index of the video stream to read. If the value is -1,
1586
the best suited video stream will be automatically selected. Default
1587
value is "-1".
1588

    
1589
@end table
1590

    
1591
This filter allows to overlay a second video on top of main input of
1592
a filtergraph as shown in this graph:
1593
@example
1594
input -----------> deltapts0 --> overlay --> output
1595
                                    ^
1596
                                    |
1597
movie --> scale--> deltapts1 -------+
1598
@end example
1599

    
1600
Some examples follow:
1601
@example
1602
# skip 3.2 seconds from the start of the avi file in.avi, and overlay it
1603
# on top of the input labelled as "in".
1604
movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1605
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1606

    
1607
# read from a video4linux2 device, and overlay it on top of the input
1608
# labelled as "in"
1609
movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1610
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1611

    
1612
@end example
1613

    
1614
@section nullsrc
1615

    
1616
Null video source, never return images. It is mainly useful as a
1617
template and to be employed in analysis / debugging tools.
1618

    
1619
It accepts as optional parameter a string of the form
1620
@var{width}:@var{height}:@var{timebase}.
1621

    
1622
@var{width} and @var{height} specify the size of the configured
1623
source. The default values of @var{width} and @var{height} are
1624
respectively 352 and 288 (corresponding to the CIF size format).
1625

    
1626
@var{timebase} specifies an arithmetic expression representing a
1627
timebase. The expression can contain the constants "PI", "E", "PHI",
1628
"AVTB" (the default timebase), and defaults to the value "AVTB".
1629

    
1630
@section frei0r_src
1631

    
1632
Provide a frei0r source.
1633

    
1634
To enable compilation of this filter you need to install the frei0r
1635
header and configure FFmpeg with --enable-frei0r.
1636

    
1637
The source supports the syntax:
1638
@example
1639
@var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
1640
@end example
1641

    
1642
@var{size} is the size of the video to generate, may be a string of the
1643
form @var{width}x@var{height} or a frame size abbreviation.
1644
@var{rate} is the rate of the video to generate, may be a string of
1645
the form @var{num}/@var{den} or a frame rate abbreviation.
1646
@var{src_name} is the name to the frei0r source to load. For more
1647
information regarding frei0r and how to set the parameters read the
1648
section "frei0r" (@pxref{frei0r}) in the description of the video
1649
filters.
1650

    
1651
Some examples follow:
1652
@example
1653
# generate a frei0r partik0l source with size 200x200 and framerate 10
1654
# which is overlayed on the overlay filter main input
1655
frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
1656
@end example
1657

    
1658
@c man end VIDEO SOURCES
1659

    
1660
@chapter Video Sinks
1661
@c man begin VIDEO SINKS
1662

    
1663
Below is a description of the currently available video sinks.
1664

    
1665
@section nullsink
1666

    
1667
Null video sink, do absolutely nothing with the input video. It is
1668
mainly useful as a template and to be employed in analysis / debugging
1669
tools.
1670

    
1671
@c man end VIDEO SINKS
1672