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@chapter Filtergraph description
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@c man begin FILTERGRAPH DESCRIPTION
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A filtergraph is a directed graph of connected filters. It can contain
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cycles, and there can be multiple links between a pair of
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filters. Each link has one input pad on one side connecting it to one
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filter from which it takes its input, and one output pad on the other
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side connecting it to the one filter accepting its output.
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Each filter in a filtergraph is an instance of a filter class
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registered in the application, which defines the features and the
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number of input and output pads of the filter.
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A filter with no input pads is called a "source", a filter with no
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output pads is called a "sink".
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@section Filtergraph syntax
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A filtergraph can be represented using a textual representation, which
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is recognized by the @code{-vf} and @code{-af} options of the ff*
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tools, and by the @code{av_parse_graph()} function defined in
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@file{libavfilter/avfiltergraph}.
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A filterchain consists of a sequence of connected filters, each one
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connected to the previous one in the sequence. A filterchain is
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represented by a list of ","-separated filter descriptions.
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A filtergraph consists of a sequence of filterchains. A sequence of
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filterchains is represented by a list of ";"-separated filterchain
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descriptions.
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A filter is represented by a string of the form:
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[@var{in_link_1}]...[@var{in_link_N}]@var{filter_name}=@var{arguments}[@var{out_link_1}]...[@var{out_link_M}]
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@var{filter_name} is the name of the filter class of which the
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described filter is an instance of, and has to be the name of one of
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the filter classes registered in the program.
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The name of the filter class is optionally followed by a string
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"=@var{arguments}".
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@var{arguments} is a string which contains the parameters used to
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initialize the filter instance, and are described in the filter
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descriptions below.
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The list of arguments can be quoted using the character "'" as initial
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and ending mark, and the character '\' for escaping the characters
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within the quoted text; otherwise the argument string is considered
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terminated when the next special character (belonging to the set
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"[]=;,") is encountered.
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The name and arguments of the filter are optionally preceded and
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followed by a list of link labels.
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A link label allows to name a link and associate it to a filter output
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or input pad. The preceding labels @var{in_link_1}
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... @var{in_link_N}, are associated to the filter input pads,
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the following labels @var{out_link_1} ... @var{out_link_M}, are
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associated to the output pads.
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When two link labels with the same name are found in the
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filtergraph, a link between the corresponding input and output pad is
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created.
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If an output pad is not labelled, it is linked by default to the first
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unlabelled input pad of the next filter in the filterchain.
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For example in the filterchain:
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@example
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nullsrc, split[L1], [L2]overlay, nullsink
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@end example
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the split filter instance has two output pads, and the overlay filter
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instance two input pads. The first output pad of split is labelled
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"L1", the first input pad of overlay is labelled "L2", and the second
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output pad of split is linked to the second input pad of overlay,
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which are both unlabelled.
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In a complete filterchain all the unlabelled filter input and output
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pads must be connected. A filtergraph is considered valid if all the
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filter input and output pads of all the filterchains are connected.
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Follows a BNF description for the filtergraph syntax:
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@example
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@var{NAME}             ::= sequence of alphanumeric characters and '_'
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@var{LINKLABEL}        ::= "[" @var{NAME} "]"
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@var{LINKLABELS}       ::= @var{LINKLABEL} [@var{LINKLABELS}]
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@var{FILTER_ARGUMENTS} ::= sequence of chars (eventually quoted)
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@var{FILTER}           ::= [@var{LINKNAMES}] @var{NAME} ["=" @var{ARGUMENTS}] [@var{LINKNAMES}]
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@var{FILTERCHAIN}      ::= @var{FILTER} [,@var{FILTERCHAIN}]
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@var{FILTERGRAPH}      ::= @var{FILTERCHAIN} [;@var{FILTERGRAPH}]
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@end example
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@c man end FILTERGRAPH DESCRIPTION
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@chapter Audio Filters
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@c man begin AUDIO FILTERS
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When you configure your Libav build, you can disable any of the
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existing filters using --disable-filters.
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The configure output will show the audio filters included in your
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build.
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Below is a description of the currently available audio filters.
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@section anull
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Pass the audio source unchanged to the output.
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@c man end AUDIO FILTERS
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@chapter Audio Sources
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@c man begin AUDIO SOURCES
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Below is a description of the currently available audio sources.
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@section anullsrc
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Null audio source, never return audio frames. It is mainly useful as a
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template and to be employed in analysis / debugging tools.
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It accepts as optional parameter a string of the form
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@var{sample_rate}:@var{channel_layout}.
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@var{sample_rate} specify the sample rate, and defaults to 44100.
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@var{channel_layout} specify the channel layout, and can be either an
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integer or a string representing a channel layout. The default value
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of @var{channel_layout} is 3, which corresponds to CH_LAYOUT_STEREO.
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Check the channel_layout_map definition in
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@file{libavcodec/audioconvert.c} for the mapping between strings and
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channel layout values.
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Follow some examples:
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@example
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#  set the sample rate to 48000 Hz and the channel layout to CH_LAYOUT_MONO.
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anullsrc=48000:4
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# same as
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anullsrc=48000:mono
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@end example
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@c man end AUDIO SOURCES
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@chapter Audio Sinks
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@c man begin AUDIO SINKS
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Below is a description of the currently available audio sinks.
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@section anullsink
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Null audio sink, do absolutely nothing with the input audio. It is
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mainly useful as a template and to be employed in analysis / debugging
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tools.
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@c man end AUDIO SINKS
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@chapter Video Filters
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@c man begin VIDEO FILTERS
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When you configure your Libav build, you can disable any of the
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existing filters using --disable-filters.
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The configure output will show the video filters included in your
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build.
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Below is a description of the currently available video filters.
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@section blackframe
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Detect frames that are (almost) completely black. Can be useful to
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detect chapter transitions or commercials. Output lines consist of
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the frame number of the detected frame, the percentage of blackness,
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the position in the file if known or -1 and the timestamp in seconds.
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In order to display the output lines, you need to set the loglevel at
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least to the AV_LOG_INFO value.
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The filter accepts the syntax:
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@example
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blackframe[=@var{amount}:[@var{threshold}]]
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@end example
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@var{amount} is the percentage of the pixels that have to be below the
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threshold, and defaults to 98.
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@var{threshold} is the threshold below which a pixel value is
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considered black, and defaults to 32.
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@section copy
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Copy the input source unchanged to the output. Mainly useful for
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testing purposes.
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@section crop
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Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}.
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The parameters are expressions containing the following constants:
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@table @option
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@item E, PI, PHI
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the corresponding mathematical approximated values for e
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(euler number), pi (greek PI), PHI (golden ratio)
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@item x, y
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the computed values for @var{x} and @var{y}. They are evaluated for
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each new frame.
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@item in_w, in_h
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the input width and heigth
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@item iw, ih
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same as @var{in_w} and @var{in_h}
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@item out_w, out_h
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the output (cropped) width and heigth
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@item ow, oh
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same as @var{out_w} and @var{out_h}
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@item n
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the number of input frame, starting from 0
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@item pos
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the position in the file of the input frame, NAN if unknown
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@item t
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timestamp expressed in seconds, NAN if the input timestamp is unknown
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@end table
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The @var{out_w} and @var{out_h} parameters specify the expressions for
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the width and height of the output (cropped) video. They are
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evaluated just at the configuration of the filter.
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The default value of @var{out_w} is "in_w", and the default value of
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@var{out_h} is "in_h".
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The expression for @var{out_w} may depend on the value of @var{out_h},
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and the expression for @var{out_h} may depend on @var{out_w}, but they
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cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
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evaluated after @var{out_w} and @var{out_h}.
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The @var{x} and @var{y} parameters specify the expressions for the
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position of the top-left corner of the output (non-cropped) area. They
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are evaluated for each frame. If the evaluated value is not valid, it
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is approximated to the nearest valid value.
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The default value of @var{x} is "(in_w-out_w)/2", and the default
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value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
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the center of the input image.
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The expression for @var{x} may depend on @var{y}, and the expression
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for @var{y} may depend on @var{x}.
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Follow some examples:
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@example
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# crop the central input area with size 100x100
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crop=100:100
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# crop the central input area with size 2/3 of the input video
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"crop=2/3*in_w:2/3*in_h"
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# crop the input video central square
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crop=in_h
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# delimit the rectangle with the top-left corner placed at position
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# 100:100 and the right-bottom corner corresponding to the right-bottom
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# corner of the input image.
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crop=in_w-100:in_h-100:100:100
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# crop 10 pixels from the left and right borders, and 20 pixels from
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# the top and bottom borders
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"crop=in_w-2*10:in_h-2*20"
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# keep only the bottom right quarter of the input image
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"crop=in_w/2:in_h/2:in_w/2:in_h/2"
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# crop height for getting Greek harmony
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"crop=in_w:1/PHI*in_w"
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# trembling effect
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"crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)"
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# erratic camera effect depending on timestamp
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"crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
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# set x depending on the value of y
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"crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
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@end example
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@section cropdetect
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Auto-detect crop size.
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Calculate necessary cropping parameters and prints the recommended
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parameters through the logging system. The detected dimensions
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correspond to the non-black area of the input video.
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It accepts the syntax:
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@example
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cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]
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@end example
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@table @option
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@item limit
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Threshold, which can be optionally specified from nothing (0) to
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everything (255), defaults to 24.
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@item round
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Value which the width/height should be divisible by, defaults to
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16. The offset is automatically adjusted to center the video. Use 2 to
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get only even dimensions (needed for 4:2:2 video). 16 is best when
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encoding to most video codecs.
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@item reset
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Counter that determines after how many frames cropdetect will reset
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the previously detected largest video area and start over to detect
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the current optimal crop area. Defaults to 0.
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This can be useful when channel logos distort the video area. 0
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indicates never reset and return the largest area encountered during
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playback.
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@end table
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@section drawbox
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Draw a colored box on the input image.
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It accepts the syntax:
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@example
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drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}
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@end example
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@table @option
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@item x, y
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Specify the top left corner coordinates of the box. Default to 0.
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@item width, height
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Specify the width and height of the box, if 0 they are interpreted as
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the input width and height. Default to 0.
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@item color
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Specify the color of the box to write, it can be the name of a color
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(case insensitive match) or a 0xRRGGBB[AA] sequence.
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@end table
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Follow some examples:
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@example
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# draw a black box around the edge of the input image
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drawbox
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# draw a box with color red and an opacity of 50%
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drawbox=10:20:200:60:red@@0.5"
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@end example
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@section fade
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Apply fade-in/out effect to input video.
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It accepts the parameters:
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@var{type}:@var{start_frame}:@var{nb_frames}
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@var{type} specifies if the effect type, can be either "in" for
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fade-in, or "out" for a fade-out effect.
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@var{start_frame} specifies the number of the start frame for starting
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to apply the fade effect.
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@var{nb_frames} specifies the number of frames for which the fade
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effect has to last. At the end of the fade-in effect the output video
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will have the same intensity as the input video, at the end of the
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fade-out transition the output video will be completely black.
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A few usage examples follow, usable too as test scenarios.
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@example
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# fade in first 30 frames of video
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fade=in:0:30
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# fade out last 45 frames of a 200-frame video
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fade=out:155:45
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# fade in first 25 frames and fade out last 25 frames of a 1000-frame video
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fade=in:0:25, fade=out:975:25
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# make first 5 frames black, then fade in from frame 5-24
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fade=in:5:20
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@end example
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@section fieldorder
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Transform the field order of the input video.
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It accepts one parameter which specifies the required field order that
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the input interlaced video will be transformed to. The parameter can
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assume one of the following values:
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@table @option
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@item 0 or bff
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output bottom field first
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@item 1 or tff
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output top field first
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@end table
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Default value is "tff".
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Transformation is achieved by shifting the picture content up or down
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by one line, and filling the remaining line with appropriate picture content.
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This method is consistent with most broadcast field order converters.
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If the input video is not flagged as being interlaced, or it is already
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flagged as being of the required output field order then this filter does
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not alter the incoming video.
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This filter is very useful when converting to or from PAL DV material,
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which is bottom field first.
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For example:
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@example
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./ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
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@end example
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@section fifo
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Buffer input images and send them when they are requested.
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This filter is mainly useful when auto-inserted by the libavfilter
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framework.
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The filter does not take parameters.
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@section format
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Convert the input video to one of the specified pixel formats.
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Libavfilter will try to pick one that is supported for the input to
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the next filter.
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The filter accepts a list of pixel format names, separated by ":",
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for example "yuv420p:monow:rgb24".
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Some examples follow:
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@example
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# convert the input video to the format "yuv420p"
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format=yuv420p
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# convert the input video to any of the formats in the list
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format=yuv420p:yuv444p:yuv410p
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@end example
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@anchor{frei0r}
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@section frei0r
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Apply a frei0r effect to the input video.
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To enable compilation of this filter you need to install the frei0r
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header and configure Libav with --enable-frei0r.
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The filter supports the syntax:
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@example
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@var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]
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@end example
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@var{filter_name} is the name to the frei0r effect to load. If the
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environment variable @env{FREI0R_PATH} is defined, the frei0r effect
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is searched in each one of the directories specified by the colon
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separated list in @env{FREIOR_PATH}, otherwise in the standard frei0r
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paths, which are in this order: @file{HOME/.frei0r-1/lib/},
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@file{/usr/local/lib/frei0r-1/}, @file{/usr/lib/frei0r-1/}.
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@var{param1}, @var{param2}, ... , @var{paramN} specify the parameters
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for the frei0r effect.
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A frei0r effect parameter can be a boolean (whose values are specified
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with "y" and "n"), a double, a color (specified by the syntax
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@var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
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numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
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description), a position (specified by the syntax @var{X}/@var{Y},
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@var{X} and @var{Y} being float numbers) and a string.
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The number and kind of parameters depend on the loaded effect. If an
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effect parameter is not specified the default value is set.
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Some examples follow:
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@example
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# apply the distort0r effect, set the first two double parameters
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frei0r=distort0r:0.5:0.01
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# apply the colordistance effect, takes a color as first parameter
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frei0r=colordistance:0.2/0.3/0.4
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frei0r=colordistance:violet
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frei0r=colordistance:0x112233
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# apply the perspective effect, specify the top left and top right
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# image positions
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frei0r=perspective:0.2/0.2:0.8/0.2
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@end example
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For more information see:
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@url{http://piksel.org/frei0r}
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@section gradfun
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Fix the banding artifacts that are sometimes introduced into nearly flat
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regions by truncation to 8bit colordepth.
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Interpolate the gradients that should go where the bands are, and
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dither them.
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This filter is designed for playback only.  Do not use it prior to
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lossy compression, because compression tends to lose the dither and
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bring back the bands.
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The filter takes two optional parameters, separated by ':':
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@var{strength}:@var{radius}
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@var{strength} is the maximum amount by which the filter will change
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any one pixel. Also the threshold for detecting nearly flat
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regions. Acceptable values range from .51 to 255, default value is
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1.2, out-of-range values will be clipped to the valid range.
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@var{radius} is the neighborhood to fit the gradient to. A larger
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radius makes for smoother gradients, but also prevents the filter from
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modifying the pixels near detailed regions. Acceptable values are
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8-32, default value is 16, out-of-range values will be clipped to the
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valid range.
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@example
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# default parameters
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gradfun=1.2:16
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# omitting radius
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gradfun=1.2
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@end example
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@section hflip
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Flip the input video horizontally.
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For example to horizontally flip the video in input with
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@file{ffmpeg}:
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@example
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ffmpeg -i in.avi -vf "hflip" out.avi
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@end example
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@section hqdn3d
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High precision/quality 3d denoise filter. This filter aims to reduce
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image noise producing smooth images and making still images really
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still. It should enhance compressibility.
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It accepts the following optional parameters:
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@var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
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@table @option
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@item luma_spatial
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a non-negative float number which specifies spatial luma strength,
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defaults to 4.0
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@item chroma_spatial
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a non-negative float number which specifies spatial chroma strength,
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defaults to 3.0*@var{luma_spatial}/4.0
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@item luma_tmp
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a float number which specifies luma temporal strength, defaults to
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6.0*@var{luma_spatial}/4.0
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@item chroma_tmp
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a float number which specifies chroma temporal strength, defaults to
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@var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
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@end table
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@section noformat
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Force libavfilter not to use any of the specified pixel formats for the
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input to the next filter.
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The filter accepts a list of pixel format names, separated by ":",
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for example "yuv420p:monow:rgb24".
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Some examples follow:
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@example
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# force libavfilter to use a format different from "yuv420p" for the
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# input to the vflip filter
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noformat=yuv420p,vflip
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# convert the input video to any of the formats not contained in the list
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noformat=yuv420p:yuv444p:yuv410p
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@end example
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@section null
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Pass the video source unchanged to the output.
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@section ocv
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Apply video transform using libopencv.
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To enable this filter install libopencv library and headers and
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configure Libav with --enable-libopencv.
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The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
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@var{filter_name} is the name of the libopencv filter to apply.
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@var{filter_params} specifies the parameters to pass to the libopencv
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filter. If not specified the default values are assumed.
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Refer to the official libopencv documentation for more precise
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informations:
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@url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
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Follows the list of supported libopencv filters.
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@anchor{dilate}
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@subsection dilate
614

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

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

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

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

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

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

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

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

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

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

    
659
@subsection erode
660

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

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

    
668
@subsection smooth
669

    
670
Smooth the input video.
671

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

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

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

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

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

    
690
@section overlay
691

    
692
Overlay one video on top of another.
693

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

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

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

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

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

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

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

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

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

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

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

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

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

    
748
@section pad
749

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

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

    
756
Follows the description of the accepted parameters.
757

    
758
@table @option
759
@item width, height
760

    
761
Specify the size of the output image with the paddings added. If the
762
value for @var{width} or @var{height} is 0, the corresponding input size
763
is used for the output.
764

    
765
The default value of @var{width} and @var{height} is 0.
766

    
767
@item x, y
768

    
769
Specify the offsets where to place the input image in the padded area
770
with respect to the top/left border of the output image.
771

    
772
The default value of @var{x} and @var{y} is 0.
773

    
774
@item color
775

    
776
Specify the color of the padded area, it can be the name of a color
777
(case insensitive match) or a 0xRRGGBB[AA] sequence.
778

    
779
The default value of @var{color} is "black".
780

    
781
@end table
782

    
783
For example:
784

    
785
@example
786
# Add paddings with color "violet" to the input video. Output video
787
# size is 640x480, the top-left corner of the input video is placed at
788
# column 0, row 40.
789
pad=640:480:0:40:violet
790
@end example
791

    
792
@section pixdesctest
793

    
794
Pixel format descriptor test filter, mainly useful for internal
795
testing. The output video should be equal to the input video.
796

    
797
For example:
798
@example
799
format=monow, pixdesctest
800
@end example
801

    
802
can be used to test the monowhite pixel format descriptor definition.
803

    
804
@section scale
805

    
806
Scale the input video to @var{width}:@var{height} and/or convert the image format.
807

    
808
The parameters @var{width} and @var{height} are expressions containing
809
the following constants:
810

    
811
@table @option
812
@item E, PI, PHI
813
the corresponding mathematical approximated values for e
814
(euler number), pi (greek PI), phi (golden ratio)
815

    
816
@item in_w, in_h
817
the input width and heigth
818

    
819
@item iw, ih
820
same as @var{in_w} and @var{in_h}
821

    
822
@item out_w, out_h
823
the output (cropped) width and heigth
824

    
825
@item ow, oh
826
same as @var{out_w} and @var{out_h}
827

    
828
@item a
829
input display aspect ratio, same as @var{iw} / @var{ih}
830

    
831
@item hsub, vsub
832
horizontal and vertical chroma subsample values. For example for the
833
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
834
@end table
835

    
836
If the input image format is different from the format requested by
837
the next filter, the scale filter will convert the input to the
838
requested format.
839

    
840
If the value for @var{width} or @var{height} is 0, the respective input
841
size is used for the output.
842

    
843
If the value for @var{width} or @var{height} is -1, the scale filter will
844
use, for the respective output size, a value that maintains the aspect
845
ratio of the input image.
846

    
847
The default value of @var{width} and @var{height} is 0.
848

    
849
Some examples follow:
850
@example
851
# scale the input video to a size of 200x100.
852
scale=200:100
853

    
854
# scale the input to 2x
855
scale=2*iw:2*ih
856
# the above is the same as
857
scale=2*in_w:2*in_h
858

    
859
# scale the input to half size
860
scale=iw/2:ih/2
861

    
862
# increase the width, and set the height to the same size
863
scale=3/2*iw:ow
864

    
865
# seek for Greek harmony
866
scale=iw:1/PHI*iw
867
scale=ih*PHI:ih
868

    
869
# increase the height, and set the width to 3/2 of the height
870
scale=3/2*oh:3/5*ih
871

    
872
# increase the size, but make the size a multiple of the chroma
873
scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
874

    
875
# increase the width to a maximum of 500 pixels, keep the same input aspect ratio
876
scale='min(500\, iw*3/2):-1'
877
@end example
878

    
879
@anchor{setdar}
880
@section setdar
881

    
882
Set the Display Aspect Ratio for the filter output video.
883

    
884
This is done by changing the specified Sample (aka Pixel) Aspect
885
Ratio, according to the following equation:
886
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
887

    
888
Keep in mind that this filter does not modify the pixel dimensions of
889
the video frame. Also the display aspect ratio set by this filter may
890
be changed by later filters in the filterchain, e.g. in case of
891
scaling or if another "setdar" or a "setsar" filter is applied.
892

    
893
The filter accepts a parameter string which represents the wanted
894
display aspect ratio.
895
The parameter can be a floating point number string, or an expression
896
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
897
numerator and denominator of the aspect ratio.
898
If the parameter is not specified, it is assumed the value "0:1".
899

    
900
For example to change the display aspect ratio to 16:9, specify:
901
@example
902
setdar=16:9
903
# the above is equivalent to
904
setdar=1.77777
905
@end example
906

    
907
See also the "setsar" filter documentation (@pxref{setsar}).
908

    
909
@section setpts
910

    
911
Change the PTS (presentation timestamp) of the input video frames.
912

    
913
Accept in input an expression evaluated through the eval API, which
914
can contain the following constants:
915

    
916
@table @option
917
@item PTS
918
the presentation timestamp in input
919

    
920
@item PI
921
Greek PI
922

    
923
@item PHI
924
golden ratio
925

    
926
@item E
927
Euler number
928

    
929
@item N
930
the count of the input frame, starting from 0.
931

    
932
@item STARTPTS
933
the PTS of the first video frame
934

    
935
@item INTERLACED
936
tell if the current frame is interlaced
937

    
938
@item POS
939
original position in the file of the frame, or undefined if undefined
940
for the current frame
941

    
942
@item PREV_INPTS
943
previous input PTS
944

    
945
@item PREV_OUTPTS
946
previous output PTS
947

    
948
@end table
949

    
950
Some examples follow:
951

    
952
@example
953
# start counting PTS from zero
954
setpts=PTS-STARTPTS
955

    
956
# fast motion
957
setpts=0.5*PTS
958

    
959
# slow motion
960
setpts=2.0*PTS
961

    
962
# fixed rate 25 fps
963
setpts=N/(25*TB)
964

    
965
# fixed rate 25 fps with some jitter
966
setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
967
@end example
968

    
969
@anchor{setsar}
970
@section setsar
971

    
972
Set the Sample (aka Pixel) Aspect Ratio for the filter output video.
973

    
974
Note that as a consequence of the application of this filter, the
975
output display aspect ratio will change according to the following
976
equation:
977
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
978

    
979
Keep in mind that the sample aspect ratio set by this filter may be
980
changed by later filters in the filterchain, e.g. if another "setsar"
981
or a "setdar" filter is applied.
982

    
983
The filter accepts a parameter string which represents the wanted
984
sample aspect ratio.
985
The parameter can be a floating point number string, or an expression
986
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
987
numerator and denominator of the aspect ratio.
988
If the parameter is not specified, it is assumed the value "0:1".
989

    
990
For example to change the sample aspect ratio to 10:11, specify:
991
@example
992
setsar=10:11
993
@end example
994

    
995
@section settb
996

    
997
Set the timebase to use for the output frames timestamps.
998
It is mainly useful for testing timebase configuration.
999

    
1000
It accepts in input an arithmetic expression representing a rational.
1001
The expression can contain the constants "PI", "E", "PHI", "AVTB" (the
1002
default timebase), and "intb" (the input timebase).
1003

    
1004
The default value for the input is "intb".
1005

    
1006
Follow some examples.
1007

    
1008
@example
1009
# set the timebase to 1/25
1010
settb=1/25
1011

    
1012
# set the timebase to 1/10
1013
settb=0.1
1014

    
1015
#set the timebase to 1001/1000
1016
settb=1+0.001
1017

    
1018
#set the timebase to 2*intb
1019
settb=2*intb
1020

    
1021
#set the default timebase value
1022
settb=AVTB
1023
@end example
1024

    
1025
@section slicify
1026

    
1027
Pass the images of input video on to next video filter as multiple
1028
slices.
1029

    
1030
@example
1031
./ffmpeg -i in.avi -vf "slicify=32" out.avi
1032
@end example
1033

    
1034
The filter accepts the slice height as parameter. If the parameter is
1035
not specified it will use the default value of 16.
1036

    
1037
Adding this in the beginning of filter chains should make filtering
1038
faster due to better use of the memory cache.
1039

    
1040
@section transpose
1041

    
1042
Transpose rows with columns in the input video and optionally flip it.
1043

    
1044
It accepts a parameter representing an integer, which can assume the
1045
values:
1046

    
1047
@table @samp
1048
@item 0
1049
Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
1050
@example
1051
L.R     L.l
1052
. . ->  . .
1053
l.r     R.r
1054
@end example
1055

    
1056
@item 1
1057
Rotate by 90 degrees clockwise, that is:
1058
@example
1059
L.R     l.L
1060
. . ->  . .
1061
l.r     r.R
1062
@end example
1063

    
1064
@item 2
1065
Rotate by 90 degrees counterclockwise, that is:
1066
@example
1067
L.R     R.r
1068
. . ->  . .
1069
l.r     L.l
1070
@end example
1071

    
1072
@item 3
1073
Rotate by 90 degrees clockwise and vertically flip, that is:
1074
@example
1075
L.R     r.R
1076
. . ->  . .
1077
l.r     l.L
1078
@end example
1079
@end table
1080

    
1081
@section unsharp
1082

    
1083
Sharpen or blur the input video.
1084

    
1085
It accepts the following parameters:
1086
@var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
1087

    
1088
Negative values for the amount will blur the input video, while positive
1089
values will sharpen. All parameters are optional and default to the
1090
equivalent of the string '5:5:1.0:0:0:0.0'.
1091

    
1092
@table @option
1093

    
1094
@item luma_msize_x
1095
Set the luma matrix horizontal size. It can be an integer between 3
1096
and 13, default value is 5.
1097

    
1098
@item luma_msize_y
1099
Set the luma matrix vertical size. It can be an integer between 3
1100
and 13, default value is 5.
1101

    
1102
@item luma_amount
1103
Set the luma effect strength. It can be a float number between -2.0
1104
and 5.0, default value is 1.0.
1105

    
1106
@item chroma_msize_x
1107
Set the chroma matrix horizontal size. It can be an integer between 3
1108
and 13, default value is 0.
1109

    
1110
@item chroma_msize_y
1111
Set the chroma matrix vertical size. It can be an integer between 3
1112
and 13, default value is 0.
1113

    
1114
@item luma_amount
1115
Set the chroma effect strength. It can be a float number between -2.0
1116
and 5.0, default value is 0.0.
1117

    
1118
@end table
1119

    
1120
@example
1121
# Strong luma sharpen effect parameters
1122
unsharp=7:7:2.5
1123

    
1124
# Strong blur of both luma and chroma parameters
1125
unsharp=7:7:-2:7:7:-2
1126

    
1127
# Use the default values with @command{ffmpeg}
1128
./ffmpeg -i in.avi -vf "unsharp" out.mp4
1129
@end example
1130

    
1131
@section vflip
1132

    
1133
Flip the input video vertically.
1134

    
1135
@example
1136
./ffmpeg -i in.avi -vf "vflip" out.avi
1137
@end example
1138

    
1139
@section yadif
1140

    
1141
Deinterlace the input video ("yadif" means "yet another deinterlacing
1142
filter").
1143

    
1144
It accepts the optional parameters: @var{mode}:@var{parity}.
1145

    
1146
@var{mode} specifies the interlacing mode to adopt, accepts one of the
1147
following values:
1148

    
1149
@table @option
1150
@item 0
1151
output 1 frame for each frame
1152
@item 1
1153
output 1 frame for each field
1154
@item 2
1155
like 0 but skips spatial interlacing check
1156
@item 3
1157
like 1 but skips spatial interlacing check
1158
@end table
1159

    
1160
Default value is 0.
1161

    
1162
@var{parity} specifies the picture field parity assumed for the input
1163
interlaced video, accepts one of the following values:
1164

    
1165
@table @option
1166
@item 0
1167
assume bottom field first
1168
@item 1
1169
assume top field first
1170
@item -1
1171
enable automatic detection
1172
@end table
1173

    
1174
Default value is -1.
1175
If interlacing is unknown or decoder does not export this information,
1176
top field first will be assumed.
1177

    
1178
@c man end VIDEO FILTERS
1179

    
1180
@chapter Video Sources
1181
@c man begin VIDEO SOURCES
1182

    
1183
Below is a description of the currently available video sources.
1184

    
1185
@section buffer
1186

    
1187
Buffer video frames, and make them available to the filter chain.
1188

    
1189
This source is mainly intended for a programmatic use, in particular
1190
through the interface defined in @file{libavfilter/vsrc_buffer.h}.
1191

    
1192
It accepts the following parameters:
1193
@var{width}:@var{height}:@var{pix_fmt_string}:@var{timebase_num}:@var{timebase_den}:@var{sample_aspect_ratio_num}:@var{sample_aspect_ratio.den}
1194

    
1195
All the parameters need to be explicitely defined.
1196

    
1197
Follows the list of the accepted parameters.
1198

    
1199
@table @option
1200

    
1201
@item width, height
1202
Specify the width and height of the buffered video frames.
1203

    
1204
@item pix_fmt_string
1205
A string representing the pixel format of the buffered video frames.
1206
It may be a number corresponding to a pixel format, or a pixel format
1207
name.
1208

    
1209
@item timebase_num, timebase_den
1210
Specify numerator and denomitor of the timebase assumed by the
1211
timestamps of the buffered frames.
1212

    
1213
@item sample_aspect_ratio.num, sample_aspect_ratio.den
1214
Specify numerator and denominator of the sample aspect ratio assumed
1215
by the video frames.
1216
@end table
1217

    
1218
For example:
1219
@example
1220
buffer=320:240:yuv410p:1:24:1:1
1221
@end example
1222

    
1223
will instruct the source to accept video frames with size 320x240 and
1224
with format "yuv410p", assuming 1/24 as the timestamps timebase and
1225
square pixels (1:1 sample aspect ratio).
1226
Since the pixel format with name "yuv410p" corresponds to the number 6
1227
(check the enum PixelFormat definition in @file{libavutil/pixfmt.h}),
1228
this example corresponds to:
1229
@example
1230
buffer=320:240:6:1:24
1231
@end example
1232

    
1233
@section color
1234

    
1235
Provide an uniformly colored input.
1236

    
1237
It accepts the following parameters:
1238
@var{color}:@var{frame_size}:@var{frame_rate}
1239

    
1240
Follows the description of the accepted parameters.
1241

    
1242
@table @option
1243

    
1244
@item color
1245
Specify the color of the source. It can be the name of a color (case
1246
insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an
1247
alpha specifier. The default value is "black".
1248

    
1249
@item frame_size
1250
Specify the size of the sourced video, it may be a string of the form
1251
@var{width}x@var{heigth}, or the name of a size abbreviation. The
1252
default value is "320x240".
1253

    
1254
@item frame_rate
1255
Specify the frame rate of the sourced video, as the number of frames
1256
generated per second. It has to be a string in the format
1257
@var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
1258
number or a valid video frame rate abbreviation. The default value is
1259
"25".
1260

    
1261
@end table
1262

    
1263
For example the following graph description will generate a red source
1264
with an opacity of 0.2, with size "qcif" and a frame rate of 10
1265
frames per second, which will be overlayed over the source connected
1266
to the pad with identifier "in".
1267

    
1268
@example
1269
"color=red@@0.2:qcif:10 [color]; [in][color] overlay [out]"
1270
@end example
1271

    
1272
@section movie
1273

    
1274
Read a video stream from a movie container.
1275

    
1276
It accepts the syntax: @var{movie_name}[:@var{options}] where
1277
@var{movie_name} is the name of the resource to read (not necessarily
1278
a file but also a device or a stream accessed through some protocol),
1279
and @var{options} is an optional sequence of @var{key}=@var{value}
1280
pairs, separated by ":".
1281

    
1282
The description of the accepted options follows.
1283

    
1284
@table @option
1285

    
1286
@item format_name, f
1287
Specifies the format assumed for the movie to read, and can be either
1288
the name of a container or an input device. If not specified the
1289
format is guessed from @var{movie_name} or by probing.
1290

    
1291
@item seek_point, sp
1292
Specifies the seek point in seconds, the frames will be output
1293
starting from this seek point, the parameter is evaluated with
1294
@code{av_strtod} so the numerical value may be suffixed by an IS
1295
postfix. Default value is "0".
1296

    
1297
@item stream_index, si
1298
Specifies the index of the video stream to read. If the value is -1,
1299
the best suited video stream will be automatically selected. Default
1300
value is "-1".
1301

    
1302
@end table
1303

    
1304
This filter allows to overlay a second video on top of main input of
1305
a filtergraph as shown in this graph:
1306
@example
1307
input -----------> deltapts0 --> overlay --> output
1308
                                    ^
1309
                                    |
1310
movie --> scale--> deltapts1 -------+
1311
@end example
1312

    
1313
Some examples follow:
1314
@example
1315
# skip 3.2 seconds from the start of the avi file in.avi, and overlay it
1316
# on top of the input labelled as "in".
1317
movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1318
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1319

    
1320
# read from a video4linux2 device, and overlay it on top of the input
1321
# labelled as "in"
1322
movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
1323
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
1324

    
1325
@end example
1326

    
1327
@section nullsrc
1328

    
1329
Null video source, never return images. It is mainly useful as a
1330
template and to be employed in analysis / debugging tools.
1331

    
1332
It accepts as optional parameter a string of the form
1333
@var{width}:@var{height}:@var{timebase}.
1334

    
1335
@var{width} and @var{height} specify the size of the configured
1336
source. The default values of @var{width} and @var{height} are
1337
respectively 352 and 288 (corresponding to the CIF size format).
1338

    
1339
@var{timebase} specifies an arithmetic expression representing a
1340
timebase. The expression can contain the constants "PI", "E", "PHI",
1341
"AVTB" (the default timebase), and defaults to the value "AVTB".
1342

    
1343
@section frei0r_src
1344

    
1345
Provide a frei0r source.
1346

    
1347
To enable compilation of this filter you need to install the frei0r
1348
header and configure Libav with --enable-frei0r.
1349

    
1350
The source supports the syntax:
1351
@example
1352
@var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
1353
@end example
1354

    
1355
@var{size} is the size of the video to generate, may be a string of the
1356
form @var{width}x@var{height} or a frame size abbreviation.
1357
@var{rate} is the rate of the video to generate, may be a string of
1358
the form @var{num}/@var{den} or a frame rate abbreviation.
1359
@var{src_name} is the name to the frei0r source to load. For more
1360
information regarding frei0r and how to set the parameters read the
1361
section "frei0r" (@pxref{frei0r}) in the description of the video
1362
filters.
1363

    
1364
Some examples follow:
1365
@example
1366
# generate a frei0r partik0l source with size 200x200 and framerate 10
1367
# which is overlayed on the overlay filter main input
1368
frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
1369
@end example
1370

    
1371
@c man end VIDEO SOURCES
1372

    
1373
@chapter Video Sinks
1374
@c man begin VIDEO SINKS
1375

    
1376
Below is a description of the currently available video sinks.
1377

    
1378
@section nullsink
1379

    
1380
Null video sink, do absolutely nothing with the input video. It is
1381
mainly useful as a template and to be employed in analysis / debugging
1382
tools.
1383

    
1384
@c man end VIDEO SINKS
1385