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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 Libav 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 Libav 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 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:
564
@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 Libav with --enable-frei0r.
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The filter supports the syntax:
581
@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
587
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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The number and kind of parameters depend on the loaded effect. If an
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effect parameter is not specified the default value is set.
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Some examples follow:
606
@example
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# apply the distort0r effect, set the first two double parameters
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frei0r=distort0r:0.5:0.01
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# apply the colordistance effect, takes a color as first parameter
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frei0r=colordistance:0.2/0.3/0.4
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frei0r=colordistance:violet
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frei0r=colordistance:0x112233
614

    
615
# apply the perspective effect, specify the top left and top right
616
# image positions
617
frei0r=perspective:0.2/0.2:0.8/0.2
618
@end example
619

    
620
For more information see:
621
@url{http://piksel.org/frei0r}
622

    
623
@section gradfun
624

    
625
Fix the banding artifacts that are sometimes introduced into nearly flat
626
regions by truncation to 8bit colordepth.
627
Interpolate the gradients that should go where the bands are, and
628
dither them.
629

    
630
This filter is designed for playback only.  Do not use it prior to
631
lossy compression, because compression tends to lose the dither and
632
bring back the bands.
633

    
634
The filter takes two optional parameters, separated by ':':
635
@var{strength}:@var{radius}
636

    
637
@var{strength} is the maximum amount by which the filter will change
638
any one pixel. Also the threshold for detecting nearly flat
639
regions. Acceptable values range from .51 to 255, default value is
640
1.2, out-of-range values will be clipped to the valid range.
641

    
642
@var{radius} is the neighborhood to fit the gradient to. A larger
643
radius makes for smoother gradients, but also prevents the filter from
644
modifying the pixels near detailed regions. Acceptable values are
645
8-32, default value is 16, out-of-range values will be clipped to the
646
valid range.
647

    
648
@example
649
# default parameters
650
gradfun=1.2:16
651

    
652
# omitting radius
653
gradfun=1.2
654
@end example
655

    
656
@section hflip
657

    
658
Flip the input video horizontally.
659

    
660
For example to horizontally flip the video in input with
661
@file{ffmpeg}:
662
@example
663
ffmpeg -i in.avi -vf "hflip" out.avi
664
@end example
665

    
666
@section hqdn3d
667

    
668
High precision/quality 3d denoise filter. This filter aims to reduce
669
image noise producing smooth images and making still images really
670
still. It should enhance compressibility.
671

    
672
It accepts the following optional parameters:
673
@var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
674

    
675
@table @option
676
@item luma_spatial
677
a non-negative float number which specifies spatial luma strength,
678
defaults to 4.0
679

    
680
@item chroma_spatial
681
a non-negative float number which specifies spatial chroma strength,
682
defaults to 3.0*@var{luma_spatial}/4.0
683

    
684
@item luma_tmp
685
a float number which specifies luma temporal strength, defaults to
686
6.0*@var{luma_spatial}/4.0
687

    
688
@item chroma_tmp
689
a float number which specifies chroma temporal strength, defaults to
690
@var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
691
@end table
692

    
693
@section noformat
694

    
695
Force libavfilter not to use any of the specified pixel formats for the
696
input to the next filter.
697

    
698
The filter accepts a list of pixel format names, separated by ":",
699
for example "yuv420p:monow:rgb24".
700

    
701
Some examples follow:
702
@example
703
# force libavfilter to use a format different from "yuv420p" for the
704
# input to the vflip filter
705
noformat=yuv420p,vflip
706

    
707
# convert the input video to any of the formats not contained in the list
708
noformat=yuv420p:yuv444p:yuv410p
709
@end example
710

    
711
@section null
712

    
713
Pass the video source unchanged to the output.
714

    
715
@section ocv
716

    
717
Apply video transform using libopencv.
718

    
719
To enable this filter install libopencv library and headers and
720
configure Libav with --enable-libopencv.
721

    
722
The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
723

    
724
@var{filter_name} is the name of the libopencv filter to apply.
725

    
726
@var{filter_params} specifies the parameters to pass to the libopencv
727
filter. If not specified the default values are assumed.
728

    
729
Refer to the official libopencv documentation for more precise
730
informations:
731
@url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
732

    
733
Follows the list of supported libopencv filters.
734

    
735
@anchor{dilate}
736
@subsection dilate
737

    
738
Dilate an image by using a specific structuring element.
739
This filter corresponds to the libopencv function @code{cvDilate}.
740

    
741
It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
742

    
743
@var{struct_el} represents a structuring element, and has the syntax:
744
@var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
745

    
746
@var{cols} and @var{rows} represent the number of colums and rows of
747
the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
748
point, and @var{shape} the shape for the structuring element, and
749
can be one of the values "rect", "cross", "ellipse", "custom".
750

    
751
If the value for @var{shape} is "custom", it must be followed by a
752
string of the form "=@var{filename}". The file with name
753
@var{filename} is assumed to represent a binary image, with each
754
printable character corresponding to a bright pixel. When a custom
755
@var{shape} is used, @var{cols} and @var{rows} are ignored, the number
756
or columns and rows of the read file are assumed instead.
757

    
758
The default value for @var{struct_el} is "3x3+0x0/rect".
759

    
760
@var{nb_iterations} specifies the number of times the transform is
761
applied to the image, and defaults to 1.
762

    
763
Follow some example:
764
@example
765
# use the default values
766
ocv=dilate
767

    
768
# dilate using a structuring element with a 5x5 cross, iterate two times
769
ocv=dilate=5x5+2x2/cross:2
770

    
771
# read the shape from the file diamond.shape, iterate two times
772
# the file diamond.shape may contain a pattern of characters like this:
773
#   *
774
#  ***
775
# *****
776
#  ***
777
#   *
778
# the specified cols and rows are ignored (but not the anchor point coordinates)
779
ocv=0x0+2x2/custom=diamond.shape:2
780
@end example
781

    
782
@subsection erode
783

    
784
Erode an image by using a specific structuring element.
785
This filter corresponds to the libopencv function @code{cvErode}.
786

    
787
The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
788
with the same meaning and use of those of the dilate filter
789
(@pxref{dilate}).
790

    
791
@subsection smooth
792

    
793
Smooth the input video.
794

    
795
The filter takes the following parameters:
796
@var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
797

    
798
@var{type} is the type of smooth filter to apply, and can be one of
799
the following values: "blur", "blur_no_scale", "median", "gaussian",
800
"bilateral". The default value is "gaussian".
801

    
802
@var{param1}, @var{param2}, @var{param3}, and @var{param4} are
803
parameters whose meanings depend on smooth type. @var{param1} and
804
@var{param2} accept integer positive values or 0, @var{param3} and
805
@var{param4} accept float values.
806

    
807
The default value for @var{param1} is 3, the default value for the
808
other parameters is 0.
809

    
810
These parameters correspond to the parameters assigned to the
811
libopencv function @code{cvSmooth}.
812

    
813
@section overlay
814

    
815
Overlay one video on top of another.
816

    
817
It takes two inputs and one output, the first input is the "main"
818
video on which the second input is overlayed.
819

    
820
It accepts the parameters: @var{x}:@var{y}.
821

    
822
@var{x} is the x coordinate of the overlayed video on the main video,
823
@var{y} is the y coordinate. The parameters are expressions containing
824
the following parameters:
825

    
826
@table @option
827
@item main_w, main_h
828
main input width and height
829

    
830
@item W, H
831
same as @var{main_w} and @var{main_h}
832

    
833
@item overlay_w, overlay_h
834
overlay input width and height
835

    
836
@item w, h
837
same as @var{overlay_w} and @var{overlay_h}
838
@end table
839

    
840
Be aware that frames are taken from each input video in timestamp
841
order, hence, if their initial timestamps differ, it is a a good idea
842
to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
843
have them begin in the same zero timestamp, as it does the example for
844
the @var{movie} filter.
845

    
846
Follow some examples:
847
@example
848
# draw the overlay at 10 pixels from the bottom right
849
# corner of the main video.
850
overlay=main_w-overlay_w-10:main_h-overlay_h-10
851

    
852
# insert a transparent PNG logo in the bottom left corner of the input
853
movie=logo.png [logo];
854
[in][logo] overlay=10:main_h-overlay_h-10 [out]
855

    
856
# insert 2 different transparent PNG logos (second logo on bottom
857
# right corner):
858
movie=logo1.png [logo1];
859
movie=logo2.png [logo2];
860
[in][logo1]       overlay=10:H-h-10 [in+logo1];
861
[in+logo1][logo2] overlay=W-w-10:H-h-10 [out]
862

    
863
# add a transparent color layer on top of the main video,
864
# WxH specifies the size of the main input to the overlay filter
865
color=red@.3:WxH [over]; [in][over] overlay [out]
866
@end example
867

    
868
You can chain togheter more overlays but the efficiency of such
869
approach is yet to be tested.
870

    
871
@section pad
872

    
873
Add paddings to the input image, and places the original input at the
874
given coordinates @var{x}, @var{y}.
875

    
876
It accepts the following parameters:
877
@var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
878

    
879
The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
880
expressions containing the following constants:
881

    
882
@table @option
883
@item E, PI, PHI
884
the corresponding mathematical approximated values for e
885
(euler number), pi (greek PI), phi (golden ratio)
886

    
887
@item in_w, in_h
888
the input video width and heigth
889

    
890
@item iw, ih
891
same as @var{in_w} and @var{in_h}
892

    
893
@item out_w, out_h
894
the output width and heigth, that is the size of the padded area as
895
specified by the @var{width} and @var{height} expressions
896

    
897
@item ow, oh
898
same as @var{out_w} and @var{out_h}
899

    
900
@item x, y
901
x and y offsets as specified by the @var{x} and @var{y}
902
expressions, or NAN if not yet specified
903

    
904
@item a
905
input display aspect ratio, same as @var{iw} / @var{ih}
906

    
907
@item hsub, vsub
908
horizontal and vertical chroma subsample values. For example for the
909
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
910
@end table
911

    
912
Follows the description of the accepted parameters.
913

    
914
@table @option
915
@item width, height
916

    
917
Specify the size of the output image with the paddings added. If the
918
value for @var{width} or @var{height} is 0, the corresponding input size
919
is used for the output.
920

    
921
The @var{width} expression can reference the value set by the
922
@var{height} expression, and viceversa.
923

    
924
The default value of @var{width} and @var{height} is 0.
925

    
926
@item x, y
927

    
928
Specify the offsets where to place the input image in the padded area
929
with respect to the top/left border of the output image.
930

    
931
The @var{x} expression can reference the value set by the @var{y}
932
expression, and viceversa.
933

    
934
The default value of @var{x} and @var{y} is 0.
935

    
936
@item color
937

    
938
Specify the color of the padded area, it can be the name of a color
939
(case insensitive match) or a 0xRRGGBB[AA] sequence.
940

    
941
The default value of @var{color} is "black".
942

    
943
@end table
944

    
945
Some examples follow:
946

    
947
@example
948
# Add paddings with color "violet" to the input video. Output video
949
# size is 640x480, the top-left corner of the input video is placed at
950
# column 0, row 40.
951
pad=640:480:0:40:violet
952

    
953
# pad the input to get an output with dimensions increased bt 3/2,
954
# and put the input video at the center of the padded area
955
pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
956

    
957
# pad the input to get a squared output with size equal to the maximum
958
# value between the input width and height, and put the input video at
959
# the center of the padded area
960
pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
961

    
962
# pad the input to get a final w/h ratio of 16:9
963
pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
964

    
965
# double output size and put the input video in the bottom-right
966
# corner of the output padded area
967
pad="2*iw:2*ih:ow-iw:oh-ih"
968
@end example
969

    
970
@section pixdesctest
971

    
972
Pixel format descriptor test filter, mainly useful for internal
973
testing. The output video should be equal to the input video.
974

    
975
For example:
976
@example
977
format=monow, pixdesctest
978
@end example
979

    
980
can be used to test the monowhite pixel format descriptor definition.
981

    
982
@section scale
983

    
984
Scale the input video to @var{width}:@var{height} and/or convert the image format.
985

    
986
The parameters @var{width} and @var{height} are expressions containing
987
the following constants:
988

    
989
@table @option
990
@item E, PI, PHI
991
the corresponding mathematical approximated values for e
992
(euler number), pi (greek PI), phi (golden ratio)
993

    
994
@item in_w, in_h
995
the input width and heigth
996

    
997
@item iw, ih
998
same as @var{in_w} and @var{in_h}
999

    
1000
@item out_w, out_h
1001
the output (cropped) width and heigth
1002

    
1003
@item ow, oh
1004
same as @var{out_w} and @var{out_h}
1005

    
1006
@item a
1007
input display aspect ratio, same as @var{iw} / @var{ih}
1008

    
1009
@item hsub, vsub
1010
horizontal and vertical chroma subsample values. For example for the
1011
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1012
@end table
1013

    
1014
If the input image format is different from the format requested by
1015
the next filter, the scale filter will convert the input to the
1016
requested format.
1017

    
1018
If the value for @var{width} or @var{height} is 0, the respective input
1019
size is used for the output.
1020

    
1021
If the value for @var{width} or @var{height} is -1, the scale filter will
1022
use, for the respective output size, a value that maintains the aspect
1023
ratio of the input image.
1024

    
1025
The default value of @var{width} and @var{height} is 0.
1026

    
1027
Some examples follow:
1028
@example
1029
# scale the input video to a size of 200x100.
1030
scale=200:100
1031

    
1032
# scale the input to 2x
1033
scale=2*iw:2*ih
1034
# the above is the same as
1035
scale=2*in_w:2*in_h
1036

    
1037
# scale the input to half size
1038
scale=iw/2:ih/2
1039

    
1040
# increase the width, and set the height to the same size
1041
scale=3/2*iw:ow
1042

    
1043
# seek for Greek harmony
1044
scale=iw:1/PHI*iw
1045
scale=ih*PHI:ih
1046

    
1047
# increase the height, and set the width to 3/2 of the height
1048
scale=3/2*oh:3/5*ih
1049

    
1050
# increase the size, but make the size a multiple of the chroma
1051
scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
1052

    
1053
# increase the width to a maximum of 500 pixels, keep the same input aspect ratio
1054
scale='min(500\, iw*3/2):-1'
1055
@end example
1056

    
1057
@anchor{setdar}
1058
@section setdar
1059

    
1060
Set the Display Aspect Ratio for the filter output video.
1061

    
1062
This is done by changing the specified Sample (aka Pixel) Aspect
1063
Ratio, according to the following equation:
1064
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
1065

    
1066
Keep in mind that this filter does not modify the pixel dimensions of
1067
the video frame. Also the display aspect ratio set by this filter may
1068
be changed by later filters in the filterchain, e.g. in case of
1069
scaling or if another "setdar" or a "setsar" filter is applied.
1070

    
1071
The filter accepts a parameter string which represents the wanted
1072
display aspect ratio.
1073
The parameter can be a floating point number string, or an expression
1074
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
1075
numerator and denominator of the aspect ratio.
1076
If the parameter is not specified, it is assumed the value "0:1".
1077

    
1078
For example to change the display aspect ratio to 16:9, specify:
1079
@example
1080
setdar=16:9
1081
# the above is equivalent to
1082
setdar=1.77777
1083
@end example
1084

    
1085
See also the "setsar" filter documentation (@pxref{setsar}).
1086

    
1087
@section setpts
1088

    
1089
Change the PTS (presentation timestamp) of the input video frames.
1090

    
1091
Accept in input an expression evaluated through the eval API, which
1092
can contain the following constants:
1093

    
1094
@table @option
1095
@item PTS
1096
the presentation timestamp in input
1097

    
1098
@item PI
1099
Greek PI
1100

    
1101
@item PHI
1102
golden ratio
1103

    
1104
@item E
1105
Euler number
1106

    
1107
@item N
1108
the count of the input frame, starting from 0.
1109

    
1110
@item STARTPTS
1111
the PTS of the first video frame
1112

    
1113
@item INTERLACED
1114
tell if the current frame is interlaced
1115

    
1116
@item POS
1117
original position in the file of the frame, or undefined if undefined
1118
for the current frame
1119

    
1120
@item PREV_INPTS
1121
previous input PTS
1122

    
1123
@item PREV_OUTPTS
1124
previous output PTS
1125

    
1126
@end table
1127

    
1128
Some examples follow:
1129

    
1130
@example
1131
# start counting PTS from zero
1132
setpts=PTS-STARTPTS
1133

    
1134
# fast motion
1135
setpts=0.5*PTS
1136

    
1137
# slow motion
1138
setpts=2.0*PTS
1139

    
1140
# fixed rate 25 fps
1141
setpts=N/(25*TB)
1142

    
1143
# fixed rate 25 fps with some jitter
1144
setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
1145
@end example
1146

    
1147
@anchor{setsar}
1148
@section setsar
1149

    
1150
Set the Sample (aka Pixel) Aspect Ratio for the filter output video.
1151

    
1152
Note that as a consequence of the application of this filter, the
1153
output display aspect ratio will change according to the following
1154
equation:
1155
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
1156

    
1157
Keep in mind that the sample aspect ratio set by this filter may be
1158
changed by later filters in the filterchain, e.g. if another "setsar"
1159
or a "setdar" filter is applied.
1160

    
1161
The filter accepts a parameter string which represents the wanted
1162
sample aspect ratio.
1163
The parameter can be a floating point number string, or an expression
1164
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
1165
numerator and denominator of the aspect ratio.
1166
If the parameter is not specified, it is assumed the value "0:1".
1167

    
1168
For example to change the sample aspect ratio to 10:11, specify:
1169
@example
1170
setsar=10:11
1171
@end example
1172

    
1173
@section settb
1174

    
1175
Set the timebase to use for the output frames timestamps.
1176
It is mainly useful for testing timebase configuration.
1177

    
1178
It accepts in input an arithmetic expression representing a rational.
1179
The expression can contain the constants "PI", "E", "PHI", "AVTB" (the
1180
default timebase), and "intb" (the input timebase).
1181

    
1182
The default value for the input is "intb".
1183

    
1184
Follow some examples.
1185

    
1186
@example
1187
# set the timebase to 1/25
1188
settb=1/25
1189

    
1190
# set the timebase to 1/10
1191
settb=0.1
1192

    
1193
#set the timebase to 1001/1000
1194
settb=1+0.001
1195

    
1196
#set the timebase to 2*intb
1197
settb=2*intb
1198

    
1199
#set the default timebase value
1200
settb=AVTB
1201
@end example
1202

    
1203
@section slicify
1204

    
1205
Pass the images of input video on to next video filter as multiple
1206
slices.
1207

    
1208
@example
1209
./ffmpeg -i in.avi -vf "slicify=32" out.avi
1210
@end example
1211

    
1212
The filter accepts the slice height as parameter. If the parameter is
1213
not specified it will use the default value of 16.
1214

    
1215
Adding this in the beginning of filter chains should make filtering
1216
faster due to better use of the memory cache.
1217

    
1218
@section transpose
1219

    
1220
Transpose rows with columns in the input video and optionally flip it.
1221

    
1222
It accepts a parameter representing an integer, which can assume the
1223
values:
1224

    
1225
@table @samp
1226
@item 0
1227
Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
1228
@example
1229
L.R     L.l
1230
. . ->  . .
1231
l.r     R.r
1232
@end example
1233

    
1234
@item 1
1235
Rotate by 90 degrees clockwise, that is:
1236
@example
1237
L.R     l.L
1238
. . ->  . .
1239
l.r     r.R
1240
@end example
1241

    
1242
@item 2
1243
Rotate by 90 degrees counterclockwise, that is:
1244
@example
1245
L.R     R.r
1246
. . ->  . .
1247
l.r     L.l
1248
@end example
1249

    
1250
@item 3
1251
Rotate by 90 degrees clockwise and vertically flip, that is:
1252
@example
1253
L.R     r.R
1254
. . ->  . .
1255
l.r     l.L
1256
@end example
1257
@end table
1258

    
1259
@section unsharp
1260

    
1261
Sharpen or blur the input video.
1262

    
1263
It accepts the following parameters:
1264
@var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
1265

    
1266
Negative values for the amount will blur the input video, while positive
1267
values will sharpen. All parameters are optional and default to the
1268
equivalent of the string '5:5:1.0:0:0:0.0'.
1269

    
1270
@table @option
1271

    
1272
@item luma_msize_x
1273
Set the luma matrix horizontal size. It can be an integer between 3
1274
and 13, default value is 5.
1275

    
1276
@item luma_msize_y
1277
Set the luma matrix vertical size. It can be an integer between 3
1278
and 13, default value is 5.
1279

    
1280
@item luma_amount
1281
Set the luma effect strength. It can be a float number between -2.0
1282
and 5.0, default value is 1.0.
1283

    
1284
@item chroma_msize_x
1285
Set the chroma matrix horizontal size. It can be an integer between 3
1286
and 13, default value is 0.
1287

    
1288
@item chroma_msize_y
1289
Set the chroma matrix vertical size. It can be an integer between 3
1290
and 13, default value is 0.
1291

    
1292
@item luma_amount
1293
Set the chroma effect strength. It can be a float number between -2.0
1294
and 5.0, default value is 0.0.
1295

    
1296
@end table
1297

    
1298
@example
1299
# Strong luma sharpen effect parameters
1300
unsharp=7:7:2.5
1301

    
1302
# Strong blur of both luma and chroma parameters
1303
unsharp=7:7:-2:7:7:-2
1304

    
1305
# Use the default values with @command{ffmpeg}
1306
./ffmpeg -i in.avi -vf "unsharp" out.mp4
1307
@end example
1308

    
1309
@section vflip
1310

    
1311
Flip the input video vertically.
1312

    
1313
@example
1314
./ffmpeg -i in.avi -vf "vflip" out.avi
1315
@end example
1316

    
1317
@section yadif
1318

    
1319
Deinterlace the input video ("yadif" means "yet another deinterlacing
1320
filter").
1321

    
1322
It accepts the optional parameters: @var{mode}:@var{parity}.
1323

    
1324
@var{mode} specifies the interlacing mode to adopt, accepts one of the
1325
following values:
1326

    
1327
@table @option
1328
@item 0
1329
output 1 frame for each frame
1330
@item 1
1331
output 1 frame for each field
1332
@item 2
1333
like 0 but skips spatial interlacing check
1334
@item 3
1335
like 1 but skips spatial interlacing check
1336
@end table
1337

    
1338
Default value is 0.
1339

    
1340
@var{parity} specifies the picture field parity assumed for the input
1341
interlaced video, accepts one of the following values:
1342

    
1343
@table @option
1344
@item 0
1345
assume bottom field first
1346
@item 1
1347
assume top field first
1348
@item -1
1349
enable automatic detection
1350
@end table
1351

    
1352
Default value is -1.
1353
If interlacing is unknown or decoder does not export this information,
1354
top field first will be assumed.
1355

    
1356
@c man end VIDEO FILTERS
1357

    
1358
@chapter Video Sources
1359
@c man begin VIDEO SOURCES
1360

    
1361
Below is a description of the currently available video sources.
1362

    
1363
@section buffer
1364

    
1365
Buffer video frames, and make them available to the filter chain.
1366

    
1367
This source is mainly intended for a programmatic use, in particular
1368
through the interface defined in @file{libavfilter/vsrc_buffer.h}.
1369

    
1370
It accepts the following parameters:
1371
@var{width}:@var{height}:@var{pix_fmt_string}:@var{timebase_num}:@var{timebase_den}:@var{sample_aspect_ratio_num}:@var{sample_aspect_ratio.den}
1372

    
1373
All the parameters need to be explicitely defined.
1374

    
1375
Follows the list of the accepted parameters.
1376

    
1377
@table @option
1378

    
1379
@item width, height
1380
Specify the width and height of the buffered video frames.
1381

    
1382
@item pix_fmt_string
1383
A string representing the pixel format of the buffered video frames.
1384
It may be a number corresponding to a pixel format, or a pixel format
1385
name.
1386

    
1387
@item timebase_num, timebase_den
1388
Specify numerator and denomitor of the timebase assumed by the
1389
timestamps of the buffered frames.
1390

    
1391
@item sample_aspect_ratio.num, sample_aspect_ratio.den
1392
Specify numerator and denominator of the sample aspect ratio assumed
1393
by the video frames.
1394
@end table
1395

    
1396
For example:
1397
@example
1398
buffer=320:240:yuv410p:1:24:1:1
1399
@end example
1400

    
1401
will instruct the source to accept video frames with size 320x240 and
1402
with format "yuv410p", assuming 1/24 as the timestamps timebase and
1403
square pixels (1:1 sample aspect ratio).
1404
Since the pixel format with name "yuv410p" corresponds to the number 6
1405
(check the enum PixelFormat definition in @file{libavutil/pixfmt.h}),
1406
this example corresponds to:
1407
@example
1408
buffer=320:240:6:1:24
1409
@end example
1410

    
1411
@section color
1412

    
1413
Provide an uniformly colored input.
1414

    
1415
It accepts the following parameters:
1416
@var{color}:@var{frame_size}:@var{frame_rate}
1417

    
1418
Follows the description of the accepted parameters.
1419

    
1420
@table @option
1421

    
1422
@item color
1423
Specify the color of the source. It can be the name of a color (case
1424
insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an
1425
alpha specifier. The default value is "black".
1426

    
1427
@item frame_size
1428
Specify the size of the sourced video, it may be a string of the form
1429
@var{width}x@var{heigth}, or the name of a size abbreviation. The
1430
default value is "320x240".
1431

    
1432
@item frame_rate
1433
Specify the frame rate of the sourced video, as the number of frames
1434
generated per second. It has to be a string in the format
1435
@var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
1436
number or a valid video frame rate abbreviation. The default value is
1437
"25".
1438

    
1439
@end table
1440

    
1441
For example the following graph description will generate a red source
1442
with an opacity of 0.2, with size "qcif" and a frame rate of 10
1443
frames per second, which will be overlayed over the source connected
1444
to the pad with identifier "in".
1445

    
1446
@example
1447
"color=red@@0.2:qcif:10 [color]; [in][color] overlay [out]"
1448
@end example
1449

    
1450
@section movie
1451

    
1452
Read a video stream from a movie container.
1453

    
1454
It accepts the syntax: @var{movie_name}[:@var{options}] where
1455
@var{movie_name} is the name of the resource to read (not necessarily
1456
a file but also a device or a stream accessed through some protocol),
1457
and @var{options} is an optional sequence of @var{key}=@var{value}
1458
pairs, separated by ":".
1459

    
1460
The description of the accepted options follows.
1461

    
1462
@table @option
1463

    
1464
@item format_name, f
1465
Specifies the format assumed for the movie to read, and can be either
1466
the name of a container or an input device. If not specified the
1467
format is guessed from @var{movie_name} or by probing.
1468

    
1469
@item seek_point, sp
1470
Specifies the seek point in seconds, the frames will be output
1471
starting from this seek point, the parameter is evaluated with
1472
@code{av_strtod} so the numerical value may be suffixed by an IS
1473
postfix. Default value is "0".
1474

    
1475
@item stream_index, si
1476
Specifies the index of the video stream to read. If the value is -1,
1477
the best suited video stream will be automatically selected. Default
1478
value is "-1".
1479

    
1480
@end table
1481

    
1482
This filter allows to overlay a second video on top of main input of
1483
a filtergraph as shown in this graph:
1484
@example
1485
input -----------> deltapts0 --> overlay --> output
1486
                                    ^
1487
                                    |
1488
movie --> scale--> deltapts1 -------+
1489
@end example
1490

    
1491
Some examples follow:
1492
@example
1493
# skip 3.2 seconds from the start of the avi file in.avi, and overlay it
1494
# on top of the input labelled as "in".
1495
movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1496
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1497

    
1498
# read from a video4linux2 device, and overlay it on top of the input
1499
# labelled as "in"
1500
movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1501
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1502

    
1503
@end example
1504

    
1505
@section nullsrc
1506

    
1507
Null video source, never return images. It is mainly useful as a
1508
template and to be employed in analysis / debugging tools.
1509

    
1510
It accepts as optional parameter a string of the form
1511
@var{width}:@var{height}:@var{timebase}.
1512

    
1513
@var{width} and @var{height} specify the size of the configured
1514
source. The default values of @var{width} and @var{height} are
1515
respectively 352 and 288 (corresponding to the CIF size format).
1516

    
1517
@var{timebase} specifies an arithmetic expression representing a
1518
timebase. The expression can contain the constants "PI", "E", "PHI",
1519
"AVTB" (the default timebase), and defaults to the value "AVTB".
1520

    
1521
@section frei0r_src
1522

    
1523
Provide a frei0r source.
1524

    
1525
To enable compilation of this filter you need to install the frei0r
1526
header and configure Libav with --enable-frei0r.
1527

    
1528
The source supports the syntax:
1529
@example
1530
@var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
1531
@end example
1532

    
1533
@var{size} is the size of the video to generate, may be a string of the
1534
form @var{width}x@var{height} or a frame size abbreviation.
1535
@var{rate} is the rate of the video to generate, may be a string of
1536
the form @var{num}/@var{den} or a frame rate abbreviation.
1537
@var{src_name} is the name to the frei0r source to load. For more
1538
information regarding frei0r and how to set the parameters read the
1539
section "frei0r" (@pxref{frei0r}) in the description of the video
1540
filters.
1541

    
1542
Some examples follow:
1543
@example
1544
# generate a frei0r partik0l source with size 200x200 and framerate 10
1545
# which is overlayed on the overlay filter main input
1546
frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
1547
@end example
1548

    
1549
@c man end VIDEO SOURCES
1550

    
1551
@chapter Video Sinks
1552
@c man begin VIDEO SINKS
1553

    
1554
Below is a description of the currently available video sinks.
1555

    
1556
@section nullsink
1557

    
1558
Null video sink, do absolutely nothing with the input video. It is
1559
mainly useful as a template and to be employed in analysis / debugging
1560
tools.
1561

    
1562
@c man end VIDEO SINKS
1563