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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 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 Libav 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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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:
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@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
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# apply the perspective effect, specify the top left and top right
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# image positions
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frei0r=perspective:0.2/0.2:0.8/0.2
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@end example
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For more information see:
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@url{http://piksel.org/frei0r}
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@section gradfun
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Fix the banding artifacts that are sometimes introduced into nearly flat
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regions by truncation to 8bit colordepth.
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Interpolate the gradients that should go where the bands are, and
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dither them.
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This filter is designed for playback only.  Do not use it prior to
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lossy compression, because compression tends to lose the dither and
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bring back the bands.
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The filter takes two optional parameters, separated by ':':
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@var{strength}:@var{radius}
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@var{strength} is the maximum amount by which the filter will change
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any one pixel. Also the threshold for detecting nearly flat
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regions. Acceptable values range from .51 to 255, default value is
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1.2, out-of-range values will be clipped to the valid range.
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@var{radius} is the neighborhood to fit the gradient to. A larger
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radius makes for smoother gradients, but also prevents the filter from
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modifying the pixels near detailed regions. Acceptable values are
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8-32, default value is 16, out-of-range values will be clipped to the
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valid range.
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@example
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# default parameters
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gradfun=1.2:16
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# omitting radius
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gradfun=1.2
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@end example
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@section hflip
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Flip the input video horizontally.
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For example to horizontally flip the video in input with
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@file{ffmpeg}:
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@example
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ffmpeg -i in.avi -vf "hflip" out.avi
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@end example
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@section hqdn3d
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High precision/quality 3d denoise filter. This filter aims to reduce
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image noise producing smooth images and making still images really
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still. It should enhance compressibility.
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It accepts the following optional parameters:
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@var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
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@table @option
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@item luma_spatial
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a non-negative float number which specifies spatial luma strength,
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defaults to 4.0
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@item chroma_spatial
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a non-negative float number which specifies spatial chroma strength,
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defaults to 3.0*@var{luma_spatial}/4.0
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@item luma_tmp
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a float number which specifies luma temporal strength, defaults to
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6.0*@var{luma_spatial}/4.0
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@item chroma_tmp
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a float number which specifies chroma temporal strength, defaults to
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@var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
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@end table
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@section noformat
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Force libavfilter not to use any of the specified pixel formats for the
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input to 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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# force libavfilter to use a format different from "yuv420p" for the
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# input to the vflip filter
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noformat=yuv420p,vflip
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# convert the input video to any of the formats not contained in the list
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noformat=yuv420p:yuv444p:yuv410p
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@end example
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@section null
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Pass the video source unchanged to the output.
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@section ocv
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Apply video transform using libopencv.
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To enable this filter install libopencv library and headers and
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configure Libav with --enable-libopencv.
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The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
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@var{filter_name} is the name of the libopencv filter to apply.
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@var{filter_params} specifies the parameters to pass to the libopencv
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filter. If not specified the default values are assumed.
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Refer to the official libopencv documentation for more precise
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informations:
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@url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
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Follows the list of supported libopencv filters.
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@anchor{dilate}
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@subsection dilate
614

    
615
Dilate an image by using a specific structuring element.
616
This filter corresponds to the libopencv function @code{cvDilate}.
617

    
618
It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
619

    
620
@var{struct_el} represents a structuring element, and has the syntax:
621
@var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
622

    
623
@var{cols} and @var{rows} represent the number of colums and rows of
624
the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
625
point, and @var{shape} the shape for the structuring element, and
626
can be one of the values "rect", "cross", "ellipse", "custom".
627

    
628
If the value for @var{shape} is "custom", it must be followed by a
629
string of the form "=@var{filename}". The file with name
630
@var{filename} is assumed to represent a binary image, with each
631
printable character corresponding to a bright pixel. When a custom
632
@var{shape} is used, @var{cols} and @var{rows} are ignored, the number
633
or columns and rows of the read file are assumed instead.
634

    
635
The default value for @var{struct_el} is "3x3+0x0/rect".
636

    
637
@var{nb_iterations} specifies the number of times the transform is
638
applied to the image, and defaults to 1.
639

    
640
Follow some example:
641
@example
642
# use the default values
643
ocv=dilate
644

    
645
# dilate using a structuring element with a 5x5 cross, iterate two times
646
ocv=dilate=5x5+2x2/cross:2
647

    
648
# read the shape from the file diamond.shape, iterate two times
649
# the file diamond.shape may contain a pattern of characters like this:
650
#   *
651
#  ***
652
# *****
653
#  ***
654
#   *
655
# the specified cols and rows are ignored (but not the anchor point coordinates)
656
ocv=0x0+2x2/custom=diamond.shape:2
657
@end example
658

    
659
@subsection erode
660

    
661
Erode an image by using a specific structuring element.
662
This filter corresponds to the libopencv function @code{cvErode}.
663

    
664
The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
665
with the same meaning and use of those of the dilate filter
666
(@pxref{dilate}).
667

    
668
@subsection smooth
669

    
670
Smooth the input video.
671

    
672
The filter takes the following parameters:
673
@var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
674

    
675
@var{type} is the type of smooth filter to apply, and can be one of
676
the following values: "blur", "blur_no_scale", "median", "gaussian",
677
"bilateral". The default value is "gaussian".
678

    
679
@var{param1}, @var{param2}, @var{param3}, and @var{param4} are
680
parameters whose meanings depend on smooth type. @var{param1} and
681
@var{param2} accept integer positive values or 0, @var{param3} and
682
@var{param4} accept float values.
683

    
684
The default value for @var{param1} is 3, the default value for the
685
other parameters is 0.
686

    
687
These parameters correspond to the parameters assigned to the
688
libopencv function @code{cvSmooth}.
689

    
690
@section overlay
691

    
692
Overlay one video on top of another.
693

    
694
It takes two inputs and one output, the first input is the "main"
695
video on which the second input is overlayed.
696

    
697
It accepts the parameters: @var{x}:@var{y}.
698

    
699
@var{x} is the x coordinate of the overlayed video on the main video,
700
@var{y} is the y coordinate. The parameters are expressions containing
701
the following parameters:
702

    
703
@table @option
704
@item main_w, main_h
705
main input width and height
706

    
707
@item W, H
708
same as @var{main_w} and @var{main_h}
709

    
710
@item overlay_w, overlay_h
711
overlay input width and height
712

    
713
@item w, h
714
same as @var{overlay_w} and @var{overlay_h}
715
@end table
716

    
717
Be aware that frames are taken from each input video in timestamp
718
order, hence, if their initial timestamps differ, it is a a good idea
719
to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
720
have them begin in the same zero timestamp, as it does the example for
721
the @var{movie} filter.
722

    
723
Follow some examples:
724
@example
725
# draw the overlay at 10 pixels from the bottom right
726
# corner of the main video.
727
overlay=main_w-overlay_w-10:main_h-overlay_h-10
728

    
729
# insert a transparent PNG logo in the bottom left corner of the input
730
movie=logo.png [logo];
731
[in][logo] overlay=10:main_h-overlay_h-10 [out]
732

    
733
# insert 2 different transparent PNG logos (second logo on bottom
734
# right corner):
735
movie=logo1.png [logo1];
736
movie=logo2.png [logo2];
737
[in][logo1]       overlay=10:H-h-10 [in+logo1];
738
[in+logo1][logo2] overlay=W-w-10:H-h-10 [out]
739

    
740
# add a transparent color layer on top of the main video,
741
# WxH specifies the size of the main input to the overlay filter
742
color=red@.3:WxH [over]; [in][over] overlay [out]
743
@end example
744

    
745
You can chain togheter more overlays but the efficiency of such
746
approach is yet to be tested.
747

    
748
@section pad
749

    
750
Add paddings to the input image, and places the original input at the
751
given coordinates @var{x}, @var{y}.
752

    
753
It accepts the following parameters:
754
@var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
755

    
756
The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
757
expressions containing the following constants:
758

    
759
@table @option
760
@item E, PI, PHI
761
the corresponding mathematical approximated values for e
762
(euler number), pi (greek PI), phi (golden ratio)
763

    
764
@item in_w, in_h
765
the input video width and heigth
766

    
767
@item iw, ih
768
same as @var{in_w} and @var{in_h}
769

    
770
@item out_w, out_h
771
the output width and heigth, that is the size of the padded area as
772
specified by the @var{width} and @var{height} expressions
773

    
774
@item ow, oh
775
same as @var{out_w} and @var{out_h}
776

    
777
@item x, y
778
x and y offsets as specified by the @var{x} and @var{y}
779
expressions, or NAN if not yet specified
780

    
781
@item a
782
input display aspect ratio, same as @var{iw} / @var{ih}
783

    
784
@item hsub, vsub
785
horizontal and vertical chroma subsample values. For example for the
786
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
787
@end table
788

    
789
Follows the description of the accepted parameters.
790

    
791
@table @option
792
@item width, height
793

    
794
Specify the size of the output image with the paddings added. If the
795
value for @var{width} or @var{height} is 0, the corresponding input size
796
is used for the output.
797

    
798
The @var{width} expression can reference the value set by the
799
@var{height} expression, and viceversa.
800

    
801
The default value of @var{width} and @var{height} is 0.
802

    
803
@item x, y
804

    
805
Specify the offsets where to place the input image in the padded area
806
with respect to the top/left border of the output image.
807

    
808
The @var{x} expression can reference the value set by the @var{y}
809
expression, and viceversa.
810

    
811
The default value of @var{x} and @var{y} is 0.
812

    
813
@item color
814

    
815
Specify the color of the padded area, it can be the name of a color
816
(case insensitive match) or a 0xRRGGBB[AA] sequence.
817

    
818
The default value of @var{color} is "black".
819

    
820
@end table
821

    
822
Some examples follow:
823

    
824
@example
825
# Add paddings with color "violet" to the input video. Output video
826
# size is 640x480, the top-left corner of the input video is placed at
827
# column 0, row 40.
828
pad=640:480:0:40:violet
829

    
830
# pad the input to get an output with dimensions increased bt 3/2,
831
# and put the input video at the center of the padded area
832
pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
833

    
834
# pad the input to get a squared output with size equal to the maximum
835
# value between the input width and height, and put the input video at
836
# the center of the padded area
837
pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
838

    
839
# pad the input to get a final w/h ratio of 16:9
840
pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
841

    
842
# double output size and put the input video in the bottom-right
843
# corner of the output padded area
844
pad="2*iw:2*ih:ow-iw:oh-ih"
845
@end example
846

    
847
@section pixdesctest
848

    
849
Pixel format descriptor test filter, mainly useful for internal
850
testing. The output video should be equal to the input video.
851

    
852
For example:
853
@example
854
format=monow, pixdesctest
855
@end example
856

    
857
can be used to test the monowhite pixel format descriptor definition.
858

    
859
@section scale
860

    
861
Scale the input video to @var{width}:@var{height} and/or convert the image format.
862

    
863
The parameters @var{width} and @var{height} are expressions containing
864
the following constants:
865

    
866
@table @option
867
@item E, PI, PHI
868
the corresponding mathematical approximated values for e
869
(euler number), pi (greek PI), phi (golden ratio)
870

    
871
@item in_w, in_h
872
the input width and heigth
873

    
874
@item iw, ih
875
same as @var{in_w} and @var{in_h}
876

    
877
@item out_w, out_h
878
the output (cropped) width and heigth
879

    
880
@item ow, oh
881
same as @var{out_w} and @var{out_h}
882

    
883
@item a
884
input display aspect ratio, same as @var{iw} / @var{ih}
885

    
886
@item hsub, vsub
887
horizontal and vertical chroma subsample values. For example for the
888
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
889
@end table
890

    
891
If the input image format is different from the format requested by
892
the next filter, the scale filter will convert the input to the
893
requested format.
894

    
895
If the value for @var{width} or @var{height} is 0, the respective input
896
size is used for the output.
897

    
898
If the value for @var{width} or @var{height} is -1, the scale filter will
899
use, for the respective output size, a value that maintains the aspect
900
ratio of the input image.
901

    
902
The default value of @var{width} and @var{height} is 0.
903

    
904
Some examples follow:
905
@example
906
# scale the input video to a size of 200x100.
907
scale=200:100
908

    
909
# scale the input to 2x
910
scale=2*iw:2*ih
911
# the above is the same as
912
scale=2*in_w:2*in_h
913

    
914
# scale the input to half size
915
scale=iw/2:ih/2
916

    
917
# increase the width, and set the height to the same size
918
scale=3/2*iw:ow
919

    
920
# seek for Greek harmony
921
scale=iw:1/PHI*iw
922
scale=ih*PHI:ih
923

    
924
# increase the height, and set the width to 3/2 of the height
925
scale=3/2*oh:3/5*ih
926

    
927
# increase the size, but make the size a multiple of the chroma
928
scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
929

    
930
# increase the width to a maximum of 500 pixels, keep the same input aspect ratio
931
scale='min(500\, iw*3/2):-1'
932
@end example
933

    
934
@anchor{setdar}
935
@section setdar
936

    
937
Set the Display Aspect Ratio for the filter output video.
938

    
939
This is done by changing the specified Sample (aka Pixel) Aspect
940
Ratio, according to the following equation:
941
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
942

    
943
Keep in mind that this filter does not modify the pixel dimensions of
944
the video frame. Also the display aspect ratio set by this filter may
945
be changed by later filters in the filterchain, e.g. in case of
946
scaling or if another "setdar" or a "setsar" filter is applied.
947

    
948
The filter accepts a parameter string which represents the wanted
949
display aspect ratio.
950
The parameter can be a floating point number string, or an expression
951
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
952
numerator and denominator of the aspect ratio.
953
If the parameter is not specified, it is assumed the value "0:1".
954

    
955
For example to change the display aspect ratio to 16:9, specify:
956
@example
957
setdar=16:9
958
# the above is equivalent to
959
setdar=1.77777
960
@end example
961

    
962
See also the "setsar" filter documentation (@pxref{setsar}).
963

    
964
@section setpts
965

    
966
Change the PTS (presentation timestamp) of the input video frames.
967

    
968
Accept in input an expression evaluated through the eval API, which
969
can contain the following constants:
970

    
971
@table @option
972
@item PTS
973
the presentation timestamp in input
974

    
975
@item PI
976
Greek PI
977

    
978
@item PHI
979
golden ratio
980

    
981
@item E
982
Euler number
983

    
984
@item N
985
the count of the input frame, starting from 0.
986

    
987
@item STARTPTS
988
the PTS of the first video frame
989

    
990
@item INTERLACED
991
tell if the current frame is interlaced
992

    
993
@item POS
994
original position in the file of the frame, or undefined if undefined
995
for the current frame
996

    
997
@item PREV_INPTS
998
previous input PTS
999

    
1000
@item PREV_OUTPTS
1001
previous output PTS
1002

    
1003
@end table
1004

    
1005
Some examples follow:
1006

    
1007
@example
1008
# start counting PTS from zero
1009
setpts=PTS-STARTPTS
1010

    
1011
# fast motion
1012
setpts=0.5*PTS
1013

    
1014
# slow motion
1015
setpts=2.0*PTS
1016

    
1017
# fixed rate 25 fps
1018
setpts=N/(25*TB)
1019

    
1020
# fixed rate 25 fps with some jitter
1021
setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
1022
@end example
1023

    
1024
@anchor{setsar}
1025
@section setsar
1026

    
1027
Set the Sample (aka Pixel) Aspect Ratio for the filter output video.
1028

    
1029
Note that as a consequence of the application of this filter, the
1030
output display aspect ratio will change according to the following
1031
equation:
1032
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
1033

    
1034
Keep in mind that the sample aspect ratio set by this filter may be
1035
changed by later filters in the filterchain, e.g. if another "setsar"
1036
or a "setdar" filter is applied.
1037

    
1038
The filter accepts a parameter string which represents the wanted
1039
sample aspect ratio.
1040
The parameter can be a floating point number string, or an expression
1041
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
1042
numerator and denominator of the aspect ratio.
1043
If the parameter is not specified, it is assumed the value "0:1".
1044

    
1045
For example to change the sample aspect ratio to 10:11, specify:
1046
@example
1047
setsar=10:11
1048
@end example
1049

    
1050
@section settb
1051

    
1052
Set the timebase to use for the output frames timestamps.
1053
It is mainly useful for testing timebase configuration.
1054

    
1055
It accepts in input an arithmetic expression representing a rational.
1056
The expression can contain the constants "PI", "E", "PHI", "AVTB" (the
1057
default timebase), and "intb" (the input timebase).
1058

    
1059
The default value for the input is "intb".
1060

    
1061
Follow some examples.
1062

    
1063
@example
1064
# set the timebase to 1/25
1065
settb=1/25
1066

    
1067
# set the timebase to 1/10
1068
settb=0.1
1069

    
1070
#set the timebase to 1001/1000
1071
settb=1+0.001
1072

    
1073
#set the timebase to 2*intb
1074
settb=2*intb
1075

    
1076
#set the default timebase value
1077
settb=AVTB
1078
@end example
1079

    
1080
@section slicify
1081

    
1082
Pass the images of input video on to next video filter as multiple
1083
slices.
1084

    
1085
@example
1086
./ffmpeg -i in.avi -vf "slicify=32" out.avi
1087
@end example
1088

    
1089
The filter accepts the slice height as parameter. If the parameter is
1090
not specified it will use the default value of 16.
1091

    
1092
Adding this in the beginning of filter chains should make filtering
1093
faster due to better use of the memory cache.
1094

    
1095
@section transpose
1096

    
1097
Transpose rows with columns in the input video and optionally flip it.
1098

    
1099
It accepts a parameter representing an integer, which can assume the
1100
values:
1101

    
1102
@table @samp
1103
@item 0
1104
Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
1105
@example
1106
L.R     L.l
1107
. . ->  . .
1108
l.r     R.r
1109
@end example
1110

    
1111
@item 1
1112
Rotate by 90 degrees clockwise, that is:
1113
@example
1114
L.R     l.L
1115
. . ->  . .
1116
l.r     r.R
1117
@end example
1118

    
1119
@item 2
1120
Rotate by 90 degrees counterclockwise, that is:
1121
@example
1122
L.R     R.r
1123
. . ->  . .
1124
l.r     L.l
1125
@end example
1126

    
1127
@item 3
1128
Rotate by 90 degrees clockwise and vertically flip, that is:
1129
@example
1130
L.R     r.R
1131
. . ->  . .
1132
l.r     l.L
1133
@end example
1134
@end table
1135

    
1136
@section unsharp
1137

    
1138
Sharpen or blur the input video.
1139

    
1140
It accepts the following parameters:
1141
@var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
1142

    
1143
Negative values for the amount will blur the input video, while positive
1144
values will sharpen. All parameters are optional and default to the
1145
equivalent of the string '5:5:1.0:0:0:0.0'.
1146

    
1147
@table @option
1148

    
1149
@item luma_msize_x
1150
Set the luma matrix horizontal size. It can be an integer between 3
1151
and 13, default value is 5.
1152

    
1153
@item luma_msize_y
1154
Set the luma matrix vertical size. It can be an integer between 3
1155
and 13, default value is 5.
1156

    
1157
@item luma_amount
1158
Set the luma effect strength. It can be a float number between -2.0
1159
and 5.0, default value is 1.0.
1160

    
1161
@item chroma_msize_x
1162
Set the chroma matrix horizontal size. It can be an integer between 3
1163
and 13, default value is 0.
1164

    
1165
@item chroma_msize_y
1166
Set the chroma matrix vertical size. It can be an integer between 3
1167
and 13, default value is 0.
1168

    
1169
@item luma_amount
1170
Set the chroma effect strength. It can be a float number between -2.0
1171
and 5.0, default value is 0.0.
1172

    
1173
@end table
1174

    
1175
@example
1176
# Strong luma sharpen effect parameters
1177
unsharp=7:7:2.5
1178

    
1179
# Strong blur of both luma and chroma parameters
1180
unsharp=7:7:-2:7:7:-2
1181

    
1182
# Use the default values with @command{ffmpeg}
1183
./ffmpeg -i in.avi -vf "unsharp" out.mp4
1184
@end example
1185

    
1186
@section vflip
1187

    
1188
Flip the input video vertically.
1189

    
1190
@example
1191
./ffmpeg -i in.avi -vf "vflip" out.avi
1192
@end example
1193

    
1194
@section yadif
1195

    
1196
Deinterlace the input video ("yadif" means "yet another deinterlacing
1197
filter").
1198

    
1199
It accepts the optional parameters: @var{mode}:@var{parity}.
1200

    
1201
@var{mode} specifies the interlacing mode to adopt, accepts one of the
1202
following values:
1203

    
1204
@table @option
1205
@item 0
1206
output 1 frame for each frame
1207
@item 1
1208
output 1 frame for each field
1209
@item 2
1210
like 0 but skips spatial interlacing check
1211
@item 3
1212
like 1 but skips spatial interlacing check
1213
@end table
1214

    
1215
Default value is 0.
1216

    
1217
@var{parity} specifies the picture field parity assumed for the input
1218
interlaced video, accepts one of the following values:
1219

    
1220
@table @option
1221
@item 0
1222
assume bottom field first
1223
@item 1
1224
assume top field first
1225
@item -1
1226
enable automatic detection
1227
@end table
1228

    
1229
Default value is -1.
1230
If interlacing is unknown or decoder does not export this information,
1231
top field first will be assumed.
1232

    
1233
@c man end VIDEO FILTERS
1234

    
1235
@chapter Video Sources
1236
@c man begin VIDEO SOURCES
1237

    
1238
Below is a description of the currently available video sources.
1239

    
1240
@section buffer
1241

    
1242
Buffer video frames, and make them available to the filter chain.
1243

    
1244
This source is mainly intended for a programmatic use, in particular
1245
through the interface defined in @file{libavfilter/vsrc_buffer.h}.
1246

    
1247
It accepts the following parameters:
1248
@var{width}:@var{height}:@var{pix_fmt_string}:@var{timebase_num}:@var{timebase_den}:@var{sample_aspect_ratio_num}:@var{sample_aspect_ratio.den}
1249

    
1250
All the parameters need to be explicitely defined.
1251

    
1252
Follows the list of the accepted parameters.
1253

    
1254
@table @option
1255

    
1256
@item width, height
1257
Specify the width and height of the buffered video frames.
1258

    
1259
@item pix_fmt_string
1260
A string representing the pixel format of the buffered video frames.
1261
It may be a number corresponding to a pixel format, or a pixel format
1262
name.
1263

    
1264
@item timebase_num, timebase_den
1265
Specify numerator and denomitor of the timebase assumed by the
1266
timestamps of the buffered frames.
1267

    
1268
@item sample_aspect_ratio.num, sample_aspect_ratio.den
1269
Specify numerator and denominator of the sample aspect ratio assumed
1270
by the video frames.
1271
@end table
1272

    
1273
For example:
1274
@example
1275
buffer=320:240:yuv410p:1:24:1:1
1276
@end example
1277

    
1278
will instruct the source to accept video frames with size 320x240 and
1279
with format "yuv410p", assuming 1/24 as the timestamps timebase and
1280
square pixels (1:1 sample aspect ratio).
1281
Since the pixel format with name "yuv410p" corresponds to the number 6
1282
(check the enum PixelFormat definition in @file{libavutil/pixfmt.h}),
1283
this example corresponds to:
1284
@example
1285
buffer=320:240:6:1:24
1286
@end example
1287

    
1288
@section color
1289

    
1290
Provide an uniformly colored input.
1291

    
1292
It accepts the following parameters:
1293
@var{color}:@var{frame_size}:@var{frame_rate}
1294

    
1295
Follows the description of the accepted parameters.
1296

    
1297
@table @option
1298

    
1299
@item color
1300
Specify the color of the source. It can be the name of a color (case
1301
insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an
1302
alpha specifier. The default value is "black".
1303

    
1304
@item frame_size
1305
Specify the size of the sourced video, it may be a string of the form
1306
@var{width}x@var{heigth}, or the name of a size abbreviation. The
1307
default value is "320x240".
1308

    
1309
@item frame_rate
1310
Specify the frame rate of the sourced video, as the number of frames
1311
generated per second. It has to be a string in the format
1312
@var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
1313
number or a valid video frame rate abbreviation. The default value is
1314
"25".
1315

    
1316
@end table
1317

    
1318
For example the following graph description will generate a red source
1319
with an opacity of 0.2, with size "qcif" and a frame rate of 10
1320
frames per second, which will be overlayed over the source connected
1321
to the pad with identifier "in".
1322

    
1323
@example
1324
"color=red@@0.2:qcif:10 [color]; [in][color] overlay [out]"
1325
@end example
1326

    
1327
@section movie
1328

    
1329
Read a video stream from a movie container.
1330

    
1331
It accepts the syntax: @var{movie_name}[:@var{options}] where
1332
@var{movie_name} is the name of the resource to read (not necessarily
1333
a file but also a device or a stream accessed through some protocol),
1334
and @var{options} is an optional sequence of @var{key}=@var{value}
1335
pairs, separated by ":".
1336

    
1337
The description of the accepted options follows.
1338

    
1339
@table @option
1340

    
1341
@item format_name, f
1342
Specifies the format assumed for the movie to read, and can be either
1343
the name of a container or an input device. If not specified the
1344
format is guessed from @var{movie_name} or by probing.
1345

    
1346
@item seek_point, sp
1347
Specifies the seek point in seconds, the frames will be output
1348
starting from this seek point, the parameter is evaluated with
1349
@code{av_strtod} so the numerical value may be suffixed by an IS
1350
postfix. Default value is "0".
1351

    
1352
@item stream_index, si
1353
Specifies the index of the video stream to read. If the value is -1,
1354
the best suited video stream will be automatically selected. Default
1355
value is "-1".
1356

    
1357
@end table
1358

    
1359
This filter allows to overlay a second video on top of main input of
1360
a filtergraph as shown in this graph:
1361
@example
1362
input -----------> deltapts0 --> overlay --> output
1363
                                    ^
1364
                                    |
1365
movie --> scale--> deltapts1 -------+
1366
@end example
1367

    
1368
Some examples follow:
1369
@example
1370
# skip 3.2 seconds from the start of the avi file in.avi, and overlay it
1371
# on top of the input labelled as "in".
1372
movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1373
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1374

    
1375
# read from a video4linux2 device, and overlay it on top of the input
1376
# labelled as "in"
1377
movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1378
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1379

    
1380
@end example
1381

    
1382
@section nullsrc
1383

    
1384
Null video source, never return images. It is mainly useful as a
1385
template and to be employed in analysis / debugging tools.
1386

    
1387
It accepts as optional parameter a string of the form
1388
@var{width}:@var{height}:@var{timebase}.
1389

    
1390
@var{width} and @var{height} specify the size of the configured
1391
source. The default values of @var{width} and @var{height} are
1392
respectively 352 and 288 (corresponding to the CIF size format).
1393

    
1394
@var{timebase} specifies an arithmetic expression representing a
1395
timebase. The expression can contain the constants "PI", "E", "PHI",
1396
"AVTB" (the default timebase), and defaults to the value "AVTB".
1397

    
1398
@section frei0r_src
1399

    
1400
Provide a frei0r source.
1401

    
1402
To enable compilation of this filter you need to install the frei0r
1403
header and configure Libav with --enable-frei0r.
1404

    
1405
The source supports the syntax:
1406
@example
1407
@var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
1408
@end example
1409

    
1410
@var{size} is the size of the video to generate, may be a string of the
1411
form @var{width}x@var{height} or a frame size abbreviation.
1412
@var{rate} is the rate of the video to generate, may be a string of
1413
the form @var{num}/@var{den} or a frame rate abbreviation.
1414
@var{src_name} is the name to the frei0r source to load. For more
1415
information regarding frei0r and how to set the parameters read the
1416
section "frei0r" (@pxref{frei0r}) in the description of the video
1417
filters.
1418

    
1419
Some examples follow:
1420
@example
1421
# generate a frei0r partik0l source with size 200x200 and framerate 10
1422
# which is overlayed on the overlay filter main input
1423
frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
1424
@end example
1425

    
1426
@c man end VIDEO SOURCES
1427

    
1428
@chapter Video Sinks
1429
@c man begin VIDEO SINKS
1430

    
1431
Below is a description of the currently available video sinks.
1432

    
1433
@section nullsink
1434

    
1435
Null video sink, do absolutely nothing with the input video. It is
1436
mainly useful as a template and to be employed in analysis / debugging
1437
tools.
1438

    
1439
@c man end VIDEO SINKS
1440