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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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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
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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.
601

    
602
The default value for @var{struct_el} is "3x3+0x0/rect".
603

    
604
@var{nb_iterations} specifies the number of times the transform is
605
applied to the image, and defaults to 1.
606

    
607
Follow some example:
608
@example
609
# use the default values
610
ocv=dilate
611

    
612
# dilate using a structuring element with a 5x5 cross, iterate two times
613
ocv=dilate=5x5+2x2/cross:2
614

    
615
# read the shape from the file diamond.shape, iterate two times
616
# the file diamond.shape may contain a pattern of characters like this:
617
#   *
618
#  ***
619
# *****
620
#  ***
621
#   *
622
# the specified cols and rows are ignored (but not the anchor point coordinates)
623
ocv=0x0+2x2/custom=diamond.shape:2
624
@end example
625

    
626
@subsection erode
627

    
628
Erode an image by using a specific structuring element.
629
This filter corresponds to the libopencv function @code{cvErode}.
630

    
631
The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
632
with the same meaning and use of those of the dilate filter
633
(@pxref{dilate}).
634

    
635
@subsection smooth
636

    
637
Smooth the input video.
638

    
639
The filter takes the following parameters:
640
@var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
641

    
642
@var{type} is the type of smooth filter to apply, and can be one of
643
the following values: "blur", "blur_no_scale", "median", "gaussian",
644
"bilateral". The default value is "gaussian".
645

    
646
@var{param1}, @var{param2}, @var{param3}, and @var{param4} are
647
parameters whose meanings depend on smooth type. @var{param1} and
648
@var{param2} accept integer positive values or 0, @var{param3} and
649
@var{param4} accept float values.
650

    
651
The default value for @var{param1} is 3, the default value for the
652
other parameters is 0.
653

    
654
These parameters correspond to the parameters assigned to the
655
libopencv function @code{cvSmooth}.
656

    
657
@section overlay
658

    
659
Overlay one video on top of another.
660

    
661
It takes two inputs and one output, the first input is the "main"
662
video on which the second input is overlayed.
663

    
664
It accepts the parameters: @var{x}:@var{y}.
665

    
666
@var{x} is the x coordinate of the overlayed video on the main video,
667
@var{y} is the y coordinate. The parameters are expressions containing
668
the following parameters:
669

    
670
@table @option
671
@item main_w, main_h
672
main input width and height
673

    
674
@item W, H
675
same as @var{main_w} and @var{main_h}
676

    
677
@item overlay_w, overlay_h
678
overlay input width and height
679

    
680
@item w, h
681
same as @var{overlay_w} and @var{overlay_h}
682
@end table
683

    
684
Be aware that frames are taken from each input video in timestamp
685
order, hence, if their initial timestamps differ, it is a a good idea
686
to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
687
have them begin in the same zero timestamp, as it does the example for
688
the @var{movie} filter.
689

    
690
Follow some examples:
691
@example
692
# draw the overlay at 10 pixels from the bottom right
693
# corner of the main video.
694
overlay=main_w-overlay_w-10:main_h-overlay_h-10
695

    
696
# insert a transparent PNG logo in the bottom left corner of the input
697
movie=logo.png [logo];
698
[in][logo] overlay=10:main_h-overlay_h-10 [out]
699

    
700
# insert 2 different transparent PNG logos (second logo on bottom
701
# right corner):
702
movie=logo1.png [logo1];
703
movie=logo2.png [logo2];
704
[in][logo1]       overlay=10:H-h-10 [in+logo1];
705
[in+logo1][logo2] overlay=W-w-10:H-h-10 [out]
706

    
707
# add a transparent color layer on top of the main video,
708
# WxH specifies the size of the main input to the overlay filter
709
color=red@.3:WxH [over]; [in][over] overlay [out]
710
@end example
711

    
712
You can chain togheter more overlays but the efficiency of such
713
approach is yet to be tested.
714

    
715
@section pad
716

    
717
Add paddings to the input image, and places the original input at the
718
given coordinates @var{x}, @var{y}.
719

    
720
It accepts the following parameters:
721
@var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
722

    
723
Follows the description of the accepted parameters.
724

    
725
@table @option
726
@item width, height
727

    
728
Specify the size of the output image with the paddings added. If the
729
value for @var{width} or @var{height} is 0, the corresponding input size
730
is used for the output.
731

    
732
The default value of @var{width} and @var{height} is 0.
733

    
734
@item x, y
735

    
736
Specify the offsets where to place the input image in the padded area
737
with respect to the top/left border of the output image.
738

    
739
The default value of @var{x} and @var{y} is 0.
740

    
741
@item color
742

    
743
Specify the color of the padded area, it can be the name of a color
744
(case insensitive match) or a 0xRRGGBB[AA] sequence.
745

    
746
The default value of @var{color} is "black".
747

    
748
@end table
749

    
750
For example:
751

    
752
@example
753
# Add paddings with color "violet" to the input video. Output video
754
# size is 640x480, the top-left corner of the input video is placed at
755
# column 0, row 40.
756
pad=640:480:0:40:violet
757
@end example
758

    
759
@section pixdesctest
760

    
761
Pixel format descriptor test filter, mainly useful for internal
762
testing. The output video should be equal to the input video.
763

    
764
For example:
765
@example
766
format=monow, pixdesctest
767
@end example
768

    
769
can be used to test the monowhite pixel format descriptor definition.
770

    
771
@section scale
772

    
773
Scale the input video to @var{width}:@var{height} and/or convert the image format.
774

    
775
For example the command:
776

    
777
@example
778
./ffmpeg -i in.avi -vf "scale=200:100" out.avi
779
@end example
780

    
781
will scale the input video to a size of 200x100.
782

    
783
If the input image format is different from the format requested by
784
the next filter, the scale filter will convert the input to the
785
requested format.
786

    
787
If the value for @var{width} or @var{height} is 0, the respective input
788
size is used for the output.
789

    
790
If the value for @var{width} or @var{height} is -1, the scale filter will
791
use, for the respective output size, a value that maintains the aspect
792
ratio of the input image.
793

    
794
The default value of @var{width} and @var{height} is 0.
795

    
796
@anchor{setdar}
797
@section setdar
798

    
799
Set the Display Aspect Ratio for the filter output video.
800

    
801
This is done by changing the specified Sample (aka Pixel) Aspect
802
Ratio, according to the following equation:
803
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
804

    
805
Keep in mind that this filter does not modify the pixel dimensions of
806
the video frame. Also the display aspect ratio set by this filter may
807
be changed by later filters in the filterchain, e.g. in case of
808
scaling or if another "setdar" or a "setsar" filter is applied.
809

    
810
The filter accepts a parameter string which represents the wanted
811
display aspect ratio.
812
The parameter can be a floating point number string, or an expression
813
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
814
numerator and denominator of the aspect ratio.
815
If the parameter is not specified, it is assumed the value "0:1".
816

    
817
For example to change the display aspect ratio to 16:9, specify:
818
@example
819
setdar=16:9
820
# the above is equivalent to
821
setdar=1.77777
822
@end example
823

    
824
See also the "setsar" filter documentation (@pxref{setsar}).
825

    
826
@section setpts
827

    
828
Change the PTS (presentation timestamp) of the input video frames.
829

    
830
Accept in input an expression evaluated through the eval API, which
831
can contain the following constants:
832

    
833
@table @option
834
@item PTS
835
the presentation timestamp in input
836

    
837
@item PI
838
Greek PI
839

    
840
@item PHI
841
golden ratio
842

    
843
@item E
844
Euler number
845

    
846
@item N
847
the count of the input frame, starting from 0.
848

    
849
@item STARTPTS
850
the PTS of the first video frame
851

    
852
@item INTERLACED
853
tell if the current frame is interlaced
854

    
855
@item POS
856
original position in the file of the frame, or undefined if undefined
857
for the current frame
858

    
859
@item PREV_INPTS
860
previous input PTS
861

    
862
@item PREV_OUTPTS
863
previous output PTS
864

    
865
@end table
866

    
867
Some examples follow:
868

    
869
@example
870
# start counting PTS from zero
871
setpts=PTS-STARTPTS
872

    
873
# fast motion
874
setpts=0.5*PTS
875

    
876
# slow motion
877
setpts=2.0*PTS
878

    
879
# fixed rate 25 fps
880
setpts=N/(25*TB)
881

    
882
# fixed rate 25 fps with some jitter
883
setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
884
@end example
885

    
886
@anchor{setsar}
887
@section setsar
888

    
889
Set the Sample (aka Pixel) Aspect Ratio for the filter output video.
890

    
891
Note that as a consequence of the application of this filter, the
892
output display aspect ratio will change according to the following
893
equation:
894
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
895

    
896
Keep in mind that the sample aspect ratio set by this filter may be
897
changed by later filters in the filterchain, e.g. if another "setsar"
898
or a "setdar" filter is applied.
899

    
900
The filter accepts a parameter string which represents the wanted
901
sample aspect ratio.
902
The parameter can be a floating point number string, or an expression
903
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
904
numerator and denominator of the aspect ratio.
905
If the parameter is not specified, it is assumed the value "0:1".
906

    
907
For example to change the sample aspect ratio to 10:11, specify:
908
@example
909
setsar=10:11
910
@end example
911

    
912
@section settb
913

    
914
Set the timebase to use for the output frames timestamps.
915
It is mainly useful for testing timebase configuration.
916

    
917
It accepts in input an arithmetic expression representing a rational.
918
The expression can contain the constants "PI", "E", "PHI", "AVTB" (the
919
default timebase), and "intb" (the input timebase).
920

    
921
The default value for the input is "intb".
922

    
923
Follow some examples.
924

    
925
@example
926
# set the timebase to 1/25
927
settb=1/25
928

    
929
# set the timebase to 1/10
930
settb=0.1
931

    
932
#set the timebase to 1001/1000
933
settb=1+0.001
934

    
935
#set the timebase to 2*intb
936
settb=2*intb
937

    
938
#set the default timebase value
939
settb=AVTB
940
@end example
941

    
942
@section slicify
943

    
944
Pass the images of input video on to next video filter as multiple
945
slices.
946

    
947
@example
948
./ffmpeg -i in.avi -vf "slicify=32" out.avi
949
@end example
950

    
951
The filter accepts the slice height as parameter. If the parameter is
952
not specified it will use the default value of 16.
953

    
954
Adding this in the beginning of filter chains should make filtering
955
faster due to better use of the memory cache.
956

    
957
@section transpose
958

    
959
Transpose rows with columns in the input video and optionally flip it.
960

    
961
It accepts a parameter representing an integer, which can assume the
962
values:
963

    
964
@table @samp
965
@item 0
966
Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
967
@example
968
L.R     L.l
969
. . ->  . .
970
l.r     R.r
971
@end example
972

    
973
@item 1
974
Rotate by 90 degrees clockwise, that is:
975
@example
976
L.R     l.L
977
. . ->  . .
978
l.r     r.R
979
@end example
980

    
981
@item 2
982
Rotate by 90 degrees counterclockwise, that is:
983
@example
984
L.R     R.r
985
. . ->  . .
986
l.r     L.l
987
@end example
988

    
989
@item 3
990
Rotate by 90 degrees clockwise and vertically flip, that is:
991
@example
992
L.R     r.R
993
. . ->  . .
994
l.r     l.L
995
@end example
996
@end table
997

    
998
@section unsharp
999

    
1000
Sharpen or blur the input video.
1001

    
1002
It accepts the following parameters:
1003
@var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
1004

    
1005
Negative values for the amount will blur the input video, while positive
1006
values will sharpen. All parameters are optional and default to the
1007
equivalent of the string '5:5:1.0:0:0:0.0'.
1008

    
1009
@table @option
1010

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

    
1015
@item luma_msize_y
1016
Set the luma matrix vertical size. It can be an integer between 3
1017
and 13, default value is 5.
1018

    
1019
@item luma_amount
1020
Set the luma effect strength. It can be a float number between -2.0
1021
and 5.0, default value is 1.0.
1022

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

    
1027
@item chroma_msize_y
1028
Set the chroma matrix vertical size. It can be an integer between 3
1029
and 13, default value is 0.
1030

    
1031
@item luma_amount
1032
Set the chroma effect strength. It can be a float number between -2.0
1033
and 5.0, default value is 0.0.
1034

    
1035
@end table
1036

    
1037
@example
1038
# Strong luma sharpen effect parameters
1039
unsharp=7:7:2.5
1040

    
1041
# Strong blur of both luma and chroma parameters
1042
unsharp=7:7:-2:7:7:-2
1043

    
1044
# Use the default values with @command{ffmpeg}
1045
./ffmpeg -i in.avi -vf "unsharp" out.mp4
1046
@end example
1047

    
1048
@section vflip
1049

    
1050
Flip the input video vertically.
1051

    
1052
@example
1053
./ffmpeg -i in.avi -vf "vflip" out.avi
1054
@end example
1055

    
1056
@section yadif
1057

    
1058
Deinterlace the input video ("yadif" means "yet another deinterlacing
1059
filter").
1060

    
1061
It accepts the optional parameters: @var{mode}:@var{parity}.
1062

    
1063
@var{mode} specifies the interlacing mode to adopt, accepts one of the
1064
following values:
1065

    
1066
@table @option
1067
@item 0
1068
output 1 frame for each frame
1069
@item 1
1070
output 1 frame for each field
1071
@item 2
1072
like 0 but skips spatial interlacing check
1073
@item 3
1074
like 1 but skips spatial interlacing check
1075
@end table
1076

    
1077
Default value is 0.
1078

    
1079
@var{parity} specifies the picture field parity assumed for the input
1080
interlaced video, accepts one of the following values:
1081

    
1082
@table @option
1083
@item 0
1084
assume bottom field first
1085
@item 1
1086
assume top field first
1087
@item -1
1088
enable automatic detection
1089
@end table
1090

    
1091
Default value is -1.
1092
If interlacing is unknown or decoder does not export this information,
1093
top field first will be assumed.
1094

    
1095
@c man end VIDEO FILTERS
1096

    
1097
@chapter Video Sources
1098
@c man begin VIDEO SOURCES
1099

    
1100
Below is a description of the currently available video sources.
1101

    
1102
@section buffer
1103

    
1104
Buffer video frames, and make them available to the filter chain.
1105

    
1106
This source is mainly intended for a programmatic use, in particular
1107
through the interface defined in @file{libavfilter/vsrc_buffer.h}.
1108

    
1109
It accepts the following parameters:
1110
@var{width}:@var{height}:@var{pix_fmt_string}:@var{timebase_num}:@var{timebase_den}
1111

    
1112
All the parameters need to be explicitely defined.
1113

    
1114
Follows the list of the accepted parameters.
1115

    
1116
@table @option
1117

    
1118
@item width, height
1119
Specify the width and height of the buffered video frames.
1120

    
1121
@item pix_fmt_string
1122
A string representing the pixel format of the buffered video frames.
1123
It may be a number corresponding to a pixel format, or a pixel format
1124
name.
1125

    
1126
@item timebase_num, timebase_den
1127
Specify numerator and denomitor of the timebase assumed by the
1128
timestamps of the buffered frames.
1129
@end table
1130

    
1131
For example:
1132
@example
1133
buffer=320:240:yuv410p:1:24
1134
@end example
1135

    
1136
will instruct the source to accept video frames with size 320x240 and
1137
with format "yuv410p" and assuming 1/24 as the timestamps timebase.
1138
Since the pixel format with name "yuv410p" corresponds to the number 6
1139
(check the enum PixelFormat definition in @file{libavutil/pixfmt.h}),
1140
this example corresponds to:
1141
@example
1142
buffer=320:240:6:1:24
1143
@end example
1144

    
1145
@section color
1146

    
1147
Provide an uniformly colored input.
1148

    
1149
It accepts the following parameters:
1150
@var{color}:@var{frame_size}:@var{frame_rate}
1151

    
1152
Follows the description of the accepted parameters.
1153

    
1154
@table @option
1155

    
1156
@item color
1157
Specify the color of the source. It can be the name of a color (case
1158
insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an
1159
alpha specifier. The default value is "black".
1160

    
1161
@item frame_size
1162
Specify the size of the sourced video, it may be a string of the form
1163
@var{width}x@var{heigth}, or the name of a size abbreviation. The
1164
default value is "320x240".
1165

    
1166
@item frame_rate
1167
Specify the frame rate of the sourced video, as the number of frames
1168
generated per second. It has to be a string in the format
1169
@var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
1170
number or a valid video frame rate abbreviation. The default value is
1171
"25".
1172

    
1173
@end table
1174

    
1175
For example the following graph description will generate a red source
1176
with an opacity of 0.2, with size "qcif" and a frame rate of 10
1177
frames per second, which will be overlayed over the source connected
1178
to the pad with identifier "in".
1179

    
1180
@example
1181
"color=red@@0.2:qcif:10 [color]; [in][color] overlay [out]"
1182
@end example
1183

    
1184
@section movie
1185

    
1186
Read a video stream from a movie container.
1187

    
1188
It accepts the syntax: @var{movie_name}[:@var{options}] where
1189
@var{movie_name} is the name of the resource to read (not necessarily
1190
a file but also a device or a stream accessed through some protocol),
1191
and @var{options} is an optional sequence of @var{key}=@var{value}
1192
pairs, separated by ":".
1193

    
1194
The description of the accepted options follows.
1195

    
1196
@table @option
1197

    
1198
@item format_name, f
1199
Specifies the format assumed for the movie to read, and can be either
1200
the name of a container or an input device. If not specified the
1201
format is guessed from @var{movie_name} or by probing.
1202

    
1203
@item seek_point, sp
1204
Specifies the seek point in seconds, the frames will be output
1205
starting from this seek point, the parameter is evaluated with
1206
@code{av_strtod} so the numerical value may be suffixed by an IS
1207
postfix. Default value is "0".
1208

    
1209
@item stream_index, si
1210
Specifies the index of the video stream to read. If the value is -1,
1211
the best suited video stream will be automatically selected. Default
1212
value is "-1".
1213

    
1214
@end table
1215

    
1216
This filter allows to overlay a second video on top of main input of
1217
a filtergraph as shown in this graph:
1218
@example
1219
input -----------> deltapts0 --> overlay --> output
1220
                                    ^
1221
                                    |
1222
movie --> scale--> deltapts1 -------+
1223
@end example
1224

    
1225
Some examples follow:
1226
@example
1227
# skip 3.2 seconds from the start of the avi file in.avi, and overlay it
1228
# on top of the input labelled as "in".
1229
movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1230
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1231

    
1232
# read from a video4linux2 device, and overlay it on top of the input
1233
# labelled as "in"
1234
movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1235
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1236

    
1237
@end example
1238

    
1239
@section nullsrc
1240

    
1241
Null video source, never return images. It is mainly useful as a
1242
template and to be employed in analysis / debugging tools.
1243

    
1244
It accepts as optional parameter a string of the form
1245
@var{width}:@var{height}:@var{timebase}.
1246

    
1247
@var{width} and @var{height} specify the size of the configured
1248
source. The default values of @var{width} and @var{height} are
1249
respectively 352 and 288 (corresponding to the CIF size format).
1250

    
1251
@var{timebase} specifies an arithmetic expression representing a
1252
timebase. The expression can contain the constants "PI", "E", "PHI",
1253
"AVTB" (the default timebase), and defaults to the value "AVTB".
1254

    
1255
@section frei0r_src
1256

    
1257
Provide a frei0r source.
1258

    
1259
To enable compilation of this filter you need to install the frei0r
1260
header and configure Libav with --enable-frei0r.
1261

    
1262
The source supports the syntax:
1263
@example
1264
@var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
1265
@end example
1266

    
1267
@var{size} is the size of the video to generate, may be a string of the
1268
form @var{width}x@var{height} or a frame size abbreviation.
1269
@var{rate} is the rate of the video to generate, may be a string of
1270
the form @var{num}/@var{den} or a frame rate abbreviation.
1271
@var{src_name} is the name to the frei0r source to load. For more
1272
information regarding frei0r and how to set the parameters read the
1273
section "frei0r" (@pxref{frei0r}) in the description of the video
1274
filters.
1275

    
1276
Some examples follow:
1277
@example
1278
# generate a frei0r partik0l source with size 200x200 and framerate 10
1279
# which is overlayed on the overlay filter main input
1280
frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
1281
@end example
1282

    
1283
@c man end VIDEO SOURCES
1284

    
1285
@chapter Video Sinks
1286
@c man begin VIDEO SINKS
1287

    
1288
Below is a description of the currently available video sinks.
1289

    
1290
@section nullsink
1291

    
1292
Null video sink, do absolutely nothing with the input video. It is
1293
mainly useful as a template and to be employed in analysis / debugging
1294
tools.
1295

    
1296
@c man end VIDEO SINKS
1297