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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 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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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
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Dilate an image by using a specific structuring element.
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This filter corresponds to the libopencv function @code{cvDilate}.
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It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
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@var{struct_el} represents a structuring element, and has the syntax:
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@var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
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@var{cols} and @var{rows} represent the number of colums and rows of
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the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
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point, and @var{shape} the shape for the structuring element, and
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can be one of the values "rect", "cross", "ellipse", "custom".
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If the value for @var{shape} is "custom", it must be followed by a
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string of the form "=@var{filename}". The file with name
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@var{filename} is assumed to represent a binary image, with each
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printable character corresponding to a bright pixel. When a custom
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@var{shape} is used, @var{cols} and @var{rows} are ignored, the number
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or columns and rows of the read file are assumed instead.
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The default value for @var{struct_el} is "3x3+0x0/rect".
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600
@var{nb_iterations} specifies the number of times the transform is
601
applied to the image, and defaults to 1.
602

    
603
Follow some example:
604
@example
605
# use the default values
606
ocv=dilate
607

    
608
# dilate using a structuring element with a 5x5 cross, iterate two times
609
ocv=dilate=5x5+2x2/cross:2
610

    
611
# read the shape from the file diamond.shape, iterate two times
612
# the file diamond.shape may contain a pattern of characters like this:
613
#   *
614
#  ***
615
# *****
616
#  ***
617
#   *
618
# the specified cols and rows are ignored (but not the anchor point coordinates)
619
ocv=0x0+2x2/custom=diamond.shape:2
620
@end example
621

    
622
@subsection erode
623

    
624
Erode an image by using a specific structuring element.
625
This filter corresponds to the libopencv function @code{cvErode}.
626

    
627
The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
628
with the same meaning and use of those of the dilate filter
629
(@pxref{dilate}).
630

    
631
@subsection smooth
632

    
633
Smooth the input video.
634

    
635
The filter takes the following parameters:
636
@var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
637

    
638
@var{type} is the type of smooth filter to apply, and can be one of
639
the following values: "blur", "blur_no_scale", "median", "gaussian",
640
"bilateral". The default value is "gaussian".
641

    
642
@var{param1}, @var{param2}, @var{param3}, and @var{param4} are
643
parameters whose meanings depend on smooth type. @var{param1} and
644
@var{param2} accept integer positive values or 0, @var{param3} and
645
@var{param4} accept float values.
646

    
647
The default value for @var{param1} is 3, the default value for the
648
other parameters is 0.
649

    
650
These parameters correspond to the parameters assigned to the
651
libopencv function @code{cvSmooth}.
652

    
653
@section overlay
654

    
655
Overlay one video on top of another.
656

    
657
It takes two inputs and one output, the first input is the "main"
658
video on which the second input is overlayed.
659

    
660
It accepts the parameters: @var{x}:@var{y}.
661

    
662
@var{x} is the x coordinate of the overlayed video on the main video,
663
@var{y} is the y coordinate. The parameters are expressions containing
664
the following parameters:
665

    
666
@table @option
667
@item main_w, main_h
668
main input width and height
669

    
670
@item W, H
671
same as @var{main_w} and @var{main_h}
672

    
673
@item overlay_w, overlay_h
674
overlay input width and height
675

    
676
@item w, h
677
same as @var{overlay_w} and @var{overlay_h}
678
@end table
679

    
680
Be aware that frames are taken from each input video in timestamp
681
order, hence, if their initial timestamps differ, it is a a good idea
682
to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
683
have them begin in the same zero timestamp, as it does the example for
684
the @var{movie} filter.
685

    
686
Follow some examples:
687
@example
688
# draw the overlay at 10 pixels from the bottom right
689
# corner of the main video.
690
overlay=main_w-overlay_w-10:main_h-overlay_h-10
691

    
692
# insert a transparent PNG logo in the bottom left corner of the input
693
movie=logo.png [logo];
694
[in][logo] overlay=10:main_h-overlay_h-10 [out]
695

    
696
# insert 2 different transparent PNG logos (second logo on bottom
697
# right corner):
698
movie=logo1.png [logo1];
699
movie=logo2.png [logo2];
700
[in][logo1]       overlay=10:H-h-10 [in+logo1];
701
[in+logo1][logo2] overlay=W-w-10:H-h-10 [out]
702

    
703
# add a transparent color layer on top of the main video,
704
# WxH specifies the size of the main input to the overlay filter
705
color=red@.3:WxH [over]; [in][over] overlay [out]
706
@end example
707

    
708
You can chain togheter more overlays but the efficiency of such
709
approach is yet to be tested.
710

    
711
@section pad
712

    
713
Add paddings to the input image, and places the original input at the
714
given coordinates @var{x}, @var{y}.
715

    
716
It accepts the following parameters:
717
@var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
718

    
719
Follows the description of the accepted parameters.
720

    
721
@table @option
722
@item width, height
723

    
724
Specify the size of the output image with the paddings added. If the
725
value for @var{width} or @var{height} is 0, the corresponding input size
726
is used for the output.
727

    
728
The default value of @var{width} and @var{height} is 0.
729

    
730
@item x, y
731

    
732
Specify the offsets where to place the input image in the padded area
733
with respect to the top/left border of the output image.
734

    
735
The default value of @var{x} and @var{y} is 0.
736

    
737
@item color
738

    
739
Specify the color of the padded area, it can be the name of a color
740
(case insensitive match) or a 0xRRGGBB[AA] sequence.
741

    
742
The default value of @var{color} is "black".
743

    
744
@end table
745

    
746
For example:
747

    
748
@example
749
# Add paddings with color "violet" to the input video. Output video
750
# size is 640x480, the top-left corner of the input video is placed at
751
# row 0, column 40.
752
pad=640:480:0:40:violet
753
@end example
754

    
755
@section pixdesctest
756

    
757
Pixel format descriptor test filter, mainly useful for internal
758
testing. The output video should be equal to the input video.
759

    
760
For example:
761
@example
762
format=monow, pixdesctest
763
@end example
764

    
765
can be used to test the monowhite pixel format descriptor definition.
766

    
767
@section scale
768

    
769
Scale the input video to @var{width}:@var{height} and/or convert the image format.
770

    
771
For example the command:
772

    
773
@example
774
./ffmpeg -i in.avi -vf "scale=200:100" out.avi
775
@end example
776

    
777
will scale the input video to a size of 200x100.
778

    
779
If the input image format is different from the format requested by
780
the next filter, the scale filter will convert the input to the
781
requested format.
782

    
783
If the value for @var{width} or @var{height} is 0, the respective input
784
size is used for the output.
785

    
786
If the value for @var{width} or @var{height} is -1, the scale filter will
787
use, for the respective output size, a value that maintains the aspect
788
ratio of the input image.
789

    
790
The default value of @var{width} and @var{height} is 0.
791

    
792
@anchor{setdar}
793
@section setdar
794

    
795
Set the Display Aspect Ratio for the filter output video.
796

    
797
This is done by changing the specified Sample (aka Pixel) Aspect
798
Ratio, according to the following equation:
799
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
800

    
801
Keep in mind that this filter does not modify the pixel dimensions of
802
the video frame. Also the display aspect ratio set by this filter may
803
be changed by later filters in the filterchain, e.g. in case of
804
scaling or if another "setdar" or a "setsar" filter is applied.
805

    
806
The filter accepts a parameter string which represents the wanted
807
display aspect ratio.
808
The parameter can be a floating point number string, or an expression
809
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
810
numerator and denominator of the aspect ratio.
811
If the parameter is not specified, it is assumed the value "0:1".
812

    
813
For example to change the display aspect ratio to 16:9, specify:
814
@example
815
setdar=16:9
816
# the above is equivalent to
817
setdar=1.77777
818
@end example
819

    
820
See also the "setsar" filter documentation (@pxref{setsar}).
821

    
822
@section setpts
823

    
824
Change the PTS (presentation timestamp) of the input video frames.
825

    
826
Accept in input an expression evaluated through the eval API, which
827
can contain the following constants:
828

    
829
@table @option
830
@item PTS
831
the presentation timestamp in input
832

    
833
@item PI
834
Greek PI
835

    
836
@item PHI
837
golden ratio
838

    
839
@item E
840
Euler number
841

    
842
@item N
843
the count of the input frame, starting from 0.
844

    
845
@item STARTPTS
846
the PTS of the first video frame
847

    
848
@item INTERLACED
849
tell if the current frame is interlaced
850

    
851
@item POS
852
original position in the file of the frame, or undefined if undefined
853
for the current frame
854

    
855
@item PREV_INPTS
856
previous input PTS
857

    
858
@item PREV_OUTPTS
859
previous output PTS
860

    
861
@end table
862

    
863
Some examples follow:
864

    
865
@example
866
# start counting PTS from zero
867
setpts=PTS-STARTPTS
868

    
869
# fast motion
870
setpts=0.5*PTS
871

    
872
# slow motion
873
setpts=2.0*PTS
874

    
875
# fixed rate 25 fps
876
setpts=N/(25*TB)
877

    
878
# fixed rate 25 fps with some jitter
879
setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
880
@end example
881

    
882
@anchor{setsar}
883
@section setsar
884

    
885
Set the Sample (aka Pixel) Aspect Ratio for the filter output video.
886

    
887
Note that as a consequence of the application of this filter, the
888
output display aspect ratio will change according to the following
889
equation:
890
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
891

    
892
Keep in mind that the sample aspect ratio set by this filter may be
893
changed by later filters in the filterchain, e.g. if another "setsar"
894
or a "setdar" filter is applied.
895

    
896
The filter accepts a parameter string which represents the wanted
897
sample aspect ratio.
898
The parameter can be a floating point number string, or an expression
899
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
900
numerator and denominator of the aspect ratio.
901
If the parameter is not specified, it is assumed the value "0:1".
902

    
903
For example to change the sample aspect ratio to 10:11, specify:
904
@example
905
setsar=10:11
906
@end example
907

    
908
@section settb
909

    
910
Set the timebase to use for the output frames timestamps.
911
It is mainly useful for testing timebase configuration.
912

    
913
It accepts in input an arithmetic expression representing a rational.
914
The expression can contain the constants "PI", "E", "PHI", "AVTB" (the
915
default timebase), and "intb" (the input timebase).
916

    
917
The default value for the input is "intb".
918

    
919
Follow some examples.
920

    
921
@example
922
# set the timebase to 1/25
923
settb=1/25
924

    
925
# set the timebase to 1/10
926
settb=0.1
927

    
928
#set the timebase to 1001/1000
929
settb=1+0.001
930

    
931
#set the timebase to 2*intb
932
settb=2*intb
933

    
934
#set the default timebase value
935
settb=AVTB
936
@end example
937

    
938
@section slicify
939

    
940
Pass the images of input video on to next video filter as multiple
941
slices.
942

    
943
@example
944
./ffmpeg -i in.avi -vf "slicify=32" out.avi
945
@end example
946

    
947
The filter accepts the slice height as parameter. If the parameter is
948
not specified it will use the default value of 16.
949

    
950
Adding this in the beginning of filter chains should make filtering
951
faster due to better use of the memory cache.
952

    
953
@section transpose
954

    
955
Transpose rows with columns in the input video and optionally flip it.
956

    
957
It accepts a parameter representing an integer, which can assume the
958
values:
959

    
960
@table @samp
961
@item 0
962
Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
963
@example
964
L.R     L.l
965
. . ->  . .
966
l.r     R.r
967
@end example
968

    
969
@item 1
970
Rotate by 90 degrees clockwise, that is:
971
@example
972
L.R     l.L
973
. . ->  . .
974
l.r     r.R
975
@end example
976

    
977
@item 2
978
Rotate by 90 degrees counterclockwise, that is:
979
@example
980
L.R     R.r
981
. . ->  . .
982
l.r     L.l
983
@end example
984

    
985
@item 3
986
Rotate by 90 degrees clockwise and vertically flip, that is:
987
@example
988
L.R     r.R
989
. . ->  . .
990
l.r     l.L
991
@end example
992
@end table
993

    
994
@section unsharp
995

    
996
Sharpen or blur the input video.
997

    
998
It accepts the following parameters:
999
@var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
1000

    
1001
Negative values for the amount will blur the input video, while positive
1002
values will sharpen. All parameters are optional and default to the
1003
equivalent of the string '5:5:1.0:0:0:0.0'.
1004

    
1005
@table @option
1006

    
1007
@item luma_msize_x
1008
Set the luma matrix horizontal size. It can be an integer between 3
1009
and 13, default value is 5.
1010

    
1011
@item luma_msize_y
1012
Set the luma matrix vertical size. It can be an integer between 3
1013
and 13, default value is 5.
1014

    
1015
@item luma_amount
1016
Set the luma effect strength. It can be a float number between -2.0
1017
and 5.0, default value is 1.0.
1018

    
1019
@item chroma_msize_x
1020
Set the chroma matrix horizontal size. It can be an integer between 3
1021
and 13, default value is 0.
1022

    
1023
@item chroma_msize_y
1024
Set the chroma matrix vertical size. It can be an integer between 3
1025
and 13, default value is 0.
1026

    
1027
@item luma_amount
1028
Set the chroma effect strength. It can be a float number between -2.0
1029
and 5.0, default value is 0.0.
1030

    
1031
@end table
1032

    
1033
@example
1034
# Strong luma sharpen effect parameters
1035
unsharp=7:7:2.5
1036

    
1037
# Strong blur of both luma and chroma parameters
1038
unsharp=7:7:-2:7:7:-2
1039

    
1040
# Use the default values with @command{ffmpeg}
1041
./ffmpeg -i in.avi -vf "unsharp" out.mp4
1042
@end example
1043

    
1044
@section vflip
1045

    
1046
Flip the input video vertically.
1047

    
1048
@example
1049
./ffmpeg -i in.avi -vf "vflip" out.avi
1050
@end example
1051

    
1052
@section yadif
1053

    
1054
Deinterlace the input video ("yadif" means "yet another deinterlacing
1055
filter").
1056

    
1057
It accepts the optional parameters: @var{mode}:@var{parity}.
1058

    
1059
@var{mode} specifies the interlacing mode to adopt, accepts one of the
1060
following values:
1061

    
1062
@table @option
1063
@item 0
1064
output 1 frame for each frame
1065
@item 1
1066
output 1 frame for each field
1067
@item 2
1068
like 0 but skips spatial interlacing check
1069
@item 3
1070
like 1 but skips spatial interlacing check
1071
@end table
1072

    
1073
Default value is 0.
1074

    
1075
@var{parity} specifies the picture field parity assumed for the input
1076
interlaced video, accepts one of the following values:
1077

    
1078
@table @option
1079
@item 0
1080
assume bottom field first
1081
@item 1
1082
assume top field first
1083
@item -1
1084
enable automatic detection
1085
@end table
1086

    
1087
Default value is -1.
1088
If interlacing is unknown or decoder does not export this information,
1089
top field first will be assumed.
1090

    
1091
@c man end VIDEO FILTERS
1092

    
1093
@chapter Video Sources
1094
@c man begin VIDEO SOURCES
1095

    
1096
Below is a description of the currently available video sources.
1097

    
1098
@section buffer
1099

    
1100
Buffer video frames, and make them available to the filter chain.
1101

    
1102
This source is mainly intended for a programmatic use, in particular
1103
through the interface defined in @file{libavfilter/vsrc_buffer.h}.
1104

    
1105
It accepts the following parameters:
1106
@var{width}:@var{height}:@var{pix_fmt_string}:@var{timebase_num}:@var{timebase_den}
1107

    
1108
All the parameters need to be explicitely defined.
1109

    
1110
Follows the list of the accepted parameters.
1111

    
1112
@table @option
1113

    
1114
@item width, height
1115
Specify the width and height of the buffered video frames.
1116

    
1117
@item pix_fmt_string
1118
A string representing the pixel format of the buffered video frames.
1119
It may be a number corresponding to a pixel format, or a pixel format
1120
name.
1121

    
1122
@item timebase_num, timebase_den
1123
Specify numerator and denomitor of the timebase assumed by the
1124
timestamps of the buffered frames.
1125
@end table
1126

    
1127
For example:
1128
@example
1129
buffer=320:240:yuv410p:1:24
1130
@end example
1131

    
1132
will instruct the source to accept video frames with size 320x240 and
1133
with format "yuv410p" and assuming 1/24 as the timestamps timebase.
1134
Since the pixel format with name "yuv410p" corresponds to the number 6
1135
(check the enum PixelFormat definition in @file{libavutil/pixfmt.h}),
1136
this example corresponds to:
1137
@example
1138
buffer=320:240:6:1:24
1139
@end example
1140

    
1141
@section color
1142

    
1143
Provide an uniformly colored input.
1144

    
1145
It accepts the following parameters:
1146
@var{color}:@var{frame_size}:@var{frame_rate}
1147

    
1148
Follows the description of the accepted parameters.
1149

    
1150
@table @option
1151

    
1152
@item color
1153
Specify the color of the source. It can be the name of a color (case
1154
insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an
1155
alpha specifier. The default value is "black".
1156

    
1157
@item frame_size
1158
Specify the size of the sourced video, it may be a string of the form
1159
@var{width}x@var{heigth}, or the name of a size abbreviation. The
1160
default value is "320x240".
1161

    
1162
@item frame_rate
1163
Specify the frame rate of the sourced video, as the number of frames
1164
generated per second. It has to be a string in the format
1165
@var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
1166
number or a valid video frame rate abbreviation. The default value is
1167
"25".
1168

    
1169
@end table
1170

    
1171
For example the following graph description will generate a red source
1172
with an opacity of 0.2, with size "qcif" and a frame rate of 10
1173
frames per second, which will be overlayed over the source connected
1174
to the pad with identifier "in".
1175

    
1176
@example
1177
"color=red@@0.2:qcif:10 [color]; [in][color] overlay [out]"
1178
@end example
1179

    
1180
@section movie
1181

    
1182
Read a video stream from a movie container.
1183

    
1184
It accepts the syntax: @var{movie_name}[:@var{options}] where
1185
@var{movie_name} is the name of the resource to read (not necessarily
1186
a file but also a device or a stream accessed through some protocol),
1187
and @var{options} is an optional sequence of @var{key}=@var{value}
1188
pairs, separated by ":".
1189

    
1190
The description of the accepted options follows.
1191

    
1192
@table @option
1193

    
1194
@item format_name, f
1195
Specifies the format assumed for the movie to read, and can be either
1196
the name of a container or an input device. If not specified the
1197
format is guessed from @var{movie_name} or by probing.
1198

    
1199
@item seek_point, sp
1200
Specifies the seek point in seconds, the frames will be output
1201
starting from this seek point, the parameter is evaluated with
1202
@code{av_strtod} so the numerical value may be suffixed by an IS
1203
postfix. Default value is "0".
1204

    
1205
@item stream_index, si
1206
Specifies the index of the video stream to read. If the value is -1,
1207
the best suited video stream will be automatically selected. Default
1208
value is "-1".
1209

    
1210
@end table
1211

    
1212
This filter allows to overlay a second video on top of main input of
1213
a filtergraph as shown in this graph:
1214
@example
1215
input -----------> deltapts0 --> overlay --> output
1216
                                    ^
1217
                                    |
1218
movie --> scale--> deltapts1 -------+
1219
@end example
1220

    
1221
Some examples follow:
1222
@example
1223
# skip 3.2 seconds from the start of the avi file in.avi, and overlay it
1224
# on top of the input labelled as "in".
1225
movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1226
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1227

    
1228
# read from a video4linux2 device, and overlay it on top of the input
1229
# labelled as "in"
1230
movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1231
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1232

    
1233
@end example
1234

    
1235
@section nullsrc
1236

    
1237
Null video source, never return images. It is mainly useful as a
1238
template and to be employed in analysis / debugging tools.
1239

    
1240
It accepts as optional parameter a string of the form
1241
@var{width}:@var{height}:@var{timebase}.
1242

    
1243
@var{width} and @var{height} specify the size of the configured
1244
source. The default values of @var{width} and @var{height} are
1245
respectively 352 and 288 (corresponding to the CIF size format).
1246

    
1247
@var{timebase} specifies an arithmetic expression representing a
1248
timebase. The expression can contain the constants "PI", "E", "PHI",
1249
"AVTB" (the default timebase), and defaults to the value "AVTB".
1250

    
1251
@section frei0r_src
1252

    
1253
Provide a frei0r source.
1254

    
1255
To enable compilation of this filter you need to install the frei0r
1256
header and configure Libav with --enable-frei0r.
1257

    
1258
The source supports the syntax:
1259
@example
1260
@var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
1261
@end example
1262

    
1263
@var{size} is the size of the video to generate, may be a string of the
1264
form @var{width}x@var{height} or a frame size abbreviation.
1265
@var{rate} is the rate of the video to generate, may be a string of
1266
the form @var{num}/@var{den} or a frame rate abbreviation.
1267
@var{src_name} is the name to the frei0r source to load. For more
1268
information regarding frei0r and how to set the parameters read the
1269
section "frei0r" (@pxref{frei0r}) in the description of the video
1270
filters.
1271

    
1272
Some examples follow:
1273
@example
1274
# generate a frei0r partik0l source with size 200x200 and framerate 10
1275
# which is overlayed on the overlay filter main input
1276
frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
1277
@end example
1278

    
1279
@c man end VIDEO SOURCES
1280

    
1281
@chapter Video Sinks
1282
@c man begin VIDEO SINKS
1283

    
1284
Below is a description of the currently available video sinks.
1285

    
1286
@section nullsink
1287

    
1288
Null video sink, do absolutely nothing with the input video. It is
1289
mainly useful as a template and to be employed in analysis / debugging
1290
tools.
1291

    
1292
@c man end VIDEO SINKS
1293