use a complex filter graph. For example, the following one:
@example
-input --> split --> fifo -----------------------> overlay --> output
- | ^
- | |
- +------> fifo --> crop --> vflip --------+
+input --> split ---------------------> overlay --> output
+ | ^
+ | |
+ +-----> crop --> vflip -------+
@end example
splits the stream in two streams, sends one stream through the crop filter
overlaying it on top. You can use the following command to achieve this:
@example
-ffmpeg -i input -vf "[in] split [T1], fifo, [T2] overlay=0:H/2 [out]; [T1] fifo, crop=iw:ih/2:0:ih/2, vflip [T2]" output
+ffmpeg -i input -vf "[in] split [T1], [T2] overlay=0:H/2 [out]; [T1] crop=iw:ih/2:0:ih/2, vflip [T2]" output
@end example
The result will be that in output the top half of the video is mirrored
Filters are loaded using the @var{-vf} or @var{-af} option passed to
@command{ffmpeg} or to @command{ffplay}. Filters in the same linear
-chain are separated by commas. In our example, @var{split, fifo,
-overlay} are in one linear chain, and @var{fifo, crop, vflip} are in
+chain are separated by commas. In our example, @var{split,
+overlay} are in one linear chain, and @var{crop, vflip} are in
another. The points where the linear chains join are labeled by names
enclosed in square brackets. In our example, that is @var{[T1]} and
@var{[T2]}. The special labels @var{[in]} and @var{[out]} are the points
drawtext=text=\'Caesar: tu quoque\, Brute\, fili mi\'
@end example
-See the @ref{quoting_and_escaping, Quoting and escaping} section for
-more information about the escaping and quoting rules adopted by
+See the ``Quoting and escaping'' section in the ffmpeg-utils manual
+for more information about the escaping and quoting rules adopted by
FFmpeg.
@c man end FILTERGRAPH DESCRIPTION
Pass the audio source unchanged to the output.
+@section apad
+
+Pad the end of a audio stream with silence, this can be used together with
+-shortest to extend audio streams to the same length as the video stream.
+
@section aresample
Resample the input audio to the specified parameters. If none are specified
@item dolby
Dolby matrixed stereo encoding
-@item dolby
+@item dplii
Dolby Pro Logic II matrixed stereo encoding
@end table
@section crop
-Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}
+Crop the input video.
-The @var{keep_aspect} parameter is optional, if specified and set to a
-non-zero value will force the output display aspect ratio to be the
-same of the input, by changing the output sample aspect ratio.
+This filter accepts a list of @var{key}=@var{value} pairs as argument,
+separated by ':'. If the key of the first options is omitted, the
+arguments are interpreted according to the syntax
+@var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}.
+
+A description of the accepted options follows:
+@table @option
+@item w, out_w
+Set the crop area width. It defaults to @code{iw}.
+This expression is evaluated only once during the filter
+configuration.
+
+@item h, out_h
+Set the crop area width. It defaults to @code{ih}.
+This expression is evaluated only once during the filter
+configuration.
+
+@item x
+Set the expression for the x top-left coordinate of the cropped area.
+It defaults to @code{(in_w-out_w)/2}.
+This expression is evaluated per-frame.
+
+@item y
+Set the expression for the y top-left coordinate of the cropped area.
+It defaults to @code{(in_h-out_h)/2}.
+This expression is evaluated per-frame.
+
+@item keep_aspect
+If set to 1 will force the output display aspect ratio
+to be the same of the input, by changing the output sample aspect
+ratio. It defaults to 0.
+@end table
The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
expressions containing the following constants:
@end table
-The @var{out_w} and @var{out_h} parameters specify the expressions for
-the width and height of the output (cropped) video. They are
-evaluated just at the configuration of the filter.
-
-The default value of @var{out_w} is "in_w", and the default value of
-@var{out_h} is "in_h".
-
The expression for @var{out_w} may depend on the value of @var{out_h},
and the expression for @var{out_h} may depend on @var{out_w}, but they
cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
are evaluated for each frame. If the evaluated value is not valid, it
is approximated to the nearest valid value.
-The default value of @var{x} is "(in_w-out_w)/2", and the default
-value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
-the center of the input image.
-
The expression for @var{x} may depend on @var{y}, and the expression
for @var{y} may depend on @var{x}.
-Follow some examples:
+@subsection Examples
+@itemize
+@item
+Crop area with size 100x100 at position (12,34).
+@example
+crop=100:100:12:34
+@end example
+
+Using named options, the example above becomes:
+@example
+crop=w=100:h=100:x=12:y=34
+@end example
+
+@item
+Crop the central input area with size 100x100:
@example
-# crop the central input area with size 100x100
crop=100:100
+@end example
-# crop the central input area with size 2/3 of the input video
-"crop=2/3*in_w:2/3*in_h"
+@item
+Crop the central input area with size 2/3 of the input video:
+@example
+crop=2/3*in_w:2/3*in_h
+@end example
-# crop the input video central square
+@item
+Crop the input video central square:
+@example
crop=in_h
+@end example
-# delimit the rectangle with the top-left corner placed at position
-# 100:100 and the right-bottom corner corresponding to the right-bottom
-# corner of the input image.
+@item
+Delimit the rectangle with the top-left corner placed at position
+100:100 and the right-bottom corner corresponding to the right-bottom
+corner of the input image:
+@example
crop=in_w-100:in_h-100:100:100
+@end example
-# crop 10 pixels from the left and right borders, and 20 pixels from
-# the top and bottom borders
-"crop=in_w-2*10:in_h-2*20"
+@item
+Crop 10 pixels from the left and right borders, and 20 pixels from
+the top and bottom borders
+@example
+crop=in_w-2*10:in_h-2*20
+@end example
-# keep only the bottom right quarter of the input image
-"crop=in_w/2:in_h/2:in_w/2:in_h/2"
+@item
+Keep only the bottom right quarter of the input image:
+@example
+crop=in_w/2:in_h/2:in_w/2:in_h/2
+@end example
-# crop height for getting Greek harmony
-"crop=in_w:1/PHI*in_w"
+@item
+Crop height for getting Greek harmony:
+@example
+crop=in_w:1/PHI*in_w
+@end example
-# trembling effect
-"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)"
+@item
+Appply trembling effect:
+@example
+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)
+@end example
-# erratic camera effect depending on timestamp
-"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)"
+@item
+Apply erratic camera effect depending on timestamp:
+@example
+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)"
+@end example
-# set x depending on the value of y
-"crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
+@item
+Set x depending on the value of y:
+@example
+crop=in_w/2:in_h/2:y:10+10*sin(n/10)
@end example
+@end itemize
@section cropdetect
lossy compression, because compression tends to lose the dither and
bring back the bands.
-The filter takes two optional parameters, separated by ':':
-@var{strength}:@var{radius}
+The filter accepts a list of options in the form of @var{key}=@var{value} pairs
+separated by ":". A description of the accepted options follows.
-@var{strength} is the maximum amount by which the filter will change
+@table @option
+
+@item strength
+The maximum amount by which the filter will change
any one pixel. Also the threshold for detecting nearly flat
-regions. Acceptable values range from .51 to 255, default value is
-1.2, out-of-range values will be clipped to the valid range.
+regions. Acceptable values range from @code{0.51} to @code{64}, default value
+is @code{1.2}.
-@var{radius} is the neighborhood to fit the gradient to. A larger
+@item radius
+The neighborhood to fit the gradient to. A larger
radius makes for smoother gradients, but also prevents the filter from
modifying the pixels near detailed regions. Acceptable values are
-8-32, default value is 16, out-of-range values will be clipped to the
-valid range.
+@code{8-32}, default value is @code{16}.
+
+@end table
+Alternatively, the options can be specified as a flat string:
+@var{strength}[:@var{radius}]
+
+@subsection Examples
+
+@itemize
+@item
+Apply the filter with a @code{3.5} strength and radius of @code{8}:
@example
-# default parameters
-gradfun=1.2:16
+gradfun=3.5:8
+@end example
-# omitting radius
-gradfun=1.2
+@item
+Specify radius, omitting the strength (which will fall-back to the default
+value):
+@example
+gradfun=radius=8
@end example
+@end itemize
+
@section hflip
Flip the input video horizontally.
Transpose rows with columns in the input video and optionally flip it.
-This filter accepts the following named parameters:
+The filter accepts parameters as a list of @var{key}=@var{value}
+pairs, separated by ':'. If the key of the first options is omitted,
+the arguments are interpreted according to the syntax
+@var{dir}:@var{passthrough}.
@table @option
@item dir
Default value is @code{none}.
@end table
+For example to rotate by 90 degrees clockwise and preserve portrait
+layout:
+@example
+transpose=dir=1:passthrough=portrait
+@end example
+
+The command above can also be specified as:
+@example
+transpose=1:portrait
+@end example
+
@section unsharp
Sharpen or blur the input video.
postfix. Default value is "0".
@item streams, s
-Specifies the streams to read. Several streams can be specified, separated
-by "+". The source will then have as many outputs, in the same order. The
-syntax is explained in the @ref{Stream specifiers} chapter. Two special
-names, "dv" and "da" specify respectively the default (best suited) video
-and audio stream. Default is "dv", or "da" if the filter is called as
-"amovie".
+Specifies the streams to read. Several streams can be specified,
+separated by "+". The source will then have as many outputs, in the
+same order. The syntax is explained in the ``Stream specifiers''
+section in the ffmpeg manual. Two special names, "dv" and "da" specify
+respectively the default (best suited) video and audio stream. Default
+is "dv", or "da" if the filter is called as "amovie".
@item stream_index, si
Specifies the index of the video stream to read. If the value is -1,
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