doc/filters: make examples a bit more consistent.
Create dedicated subsection and itemize. Not done for every filters, but a large part is done.
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Clément Bœsch
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doc/filters.texi
148
doc/filters.texi
@ -266,7 +266,7 @@ or the corresponding number value defined in @file{libavutil/channel_layout.h}.
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The special parameter "auto", signifies that the filter will
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automatically select the output format depending on the output filter.
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Some examples follow.
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@subsection Examples
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@itemize
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@item
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@ -647,6 +647,7 @@ select cubic root
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@end table
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@subsection Examples
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@itemize
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@item
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Fade in first 15 seconds of audio:
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@ -722,12 +723,17 @@ All inputs must have the same sample rate, and format.
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If inputs do not have the same duration, the output will stop with the
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shortest.
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Example: merge two mono files into a stereo stream:
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@subsection Examples
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@itemize
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@item
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Merge two mono files into a stereo stream:
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@example
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amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge
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@end example
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Example: multiple merges:
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@item
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Multiple merges:
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@example
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ffmpeg -f lavfi -i "
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amovie=input.mkv:si=0 [a0];
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@ -738,6 +744,7 @@ amovie=input.mkv:si=4 [a4];
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amovie=input.mkv:si=5 [a5];
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[a0][a1][a2][a3][a4][a5] amerge=inputs=6" -c:a pcm_s16le output.mkv
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@end example
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@end itemize
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@section amix
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@ -803,16 +810,22 @@ expresses a sample rate and @var{resampler_options} is a list of
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@var{key}=@var{value} pairs, separated by ":". See the
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ffmpeg-resampler manual for the complete list of supported options.
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For example, to resample the input audio to 44100Hz:
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@subsection Examples
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@itemize
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@item
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Resample the input audio to 44100Hz:
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@example
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aresample=44100
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@end example
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To stretch/squeeze samples to the given timestamps, with a maximum of 1000
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@item
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Stretch/squeeze samples to the given timestamps, with a maximum of 1000
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samples per second compensation:
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@example
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aresample=async=1000
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@end example
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@end itemize
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@section asetnsamples
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@ -952,15 +965,21 @@ The filter accepts exactly one parameter, the audio tempo. If not
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specified then the filter will assume nominal 1.0 tempo. Tempo must
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be in the [0.5, 2.0] range.
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For example, to slow down audio to 80% tempo:
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@subsection Examples
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@itemize
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@item
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Slow down audio to 80% tempo:
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@example
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atempo=0.8
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@end example
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For example, to speed up audio to 125% tempo:
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@item
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To speed up audio to 125% tempo:
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@example
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atempo=1.25
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@end example
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@end itemize
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@section earwax
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@ -1082,16 +1101,22 @@ Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
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specified value) or amplitude ratio. Default is -60dB, or 0.001.
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@end table
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@subsection Examples
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@itemize
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@item
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Detect 5 seconds of silence with -50dB noise tolerance:
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@example
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silencedetect=n=-50dB:d=5
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@end example
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@item
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Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
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tolerance in @file{silence.mp3}:
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@example
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ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -
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@end example
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@end itemize
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@section asyncts
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Synchronize audio data with timestamps by squeezing/stretching it and/or
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@ -1303,6 +1328,8 @@ the samples).
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All volumes are in decibels relative to the maximum PCM value.
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@subsection Examples
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Here is an excerpt of the output:
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@example
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[Parsed_volumedetect_0 @ 0xa23120] mean_volume: -27 dB
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@ -1369,7 +1396,8 @@ must be consistent.
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@end table
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For example:
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@subsection Examples
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@example
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abuffer=44100:s16p:stereo
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@end example
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@ -1442,7 +1470,6 @@ sample rate
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@subsection Examples
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@itemize
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@item
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Generate silence:
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@example
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@ -1450,7 +1477,6 @@ aevalsrc=0
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@end example
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@item
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Generate a sin signal with frequency of 440 Hz, set sample rate to
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8000 Hz:
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@example
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@ -1516,14 +1542,21 @@ Set the number of samples per requested frames.
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@end table
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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 AV_CH_LAYOUT_MONO.
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anullsrc=r=48000:cl=4
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@subsection Examples
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# same as
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@itemize
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@item
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Set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
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@example
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anullsrc=r=48000:cl=4
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@end example
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@item
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Do the same operation with a more obvious syntax:
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@example
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anullsrc=r=48000:cl=mono
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@end example
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@end itemize
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@section abuffer
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Buffer audio frames, and make them available to the filter chain.
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@ -1871,10 +1904,9 @@ Value of pixel component at current location for second video frame (bottom laye
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@end table
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@end table
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Some examples follow.
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@subsection Examples
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@itemize
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@item
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Apply transition from bottom layer to top layer in first 10 seconds:
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@example
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@ -1941,7 +1973,7 @@ corresponding value set for @option{luma_power}.
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A value of 0 will disable the effect.
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@end table
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Some examples follow.
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@subsection Examples
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@itemize
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@item
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@ -2076,6 +2108,7 @@ 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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@subsection Examples
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@itemize
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@item
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Crop area with size 100x100 at position (12,34).
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@ -2263,10 +2296,9 @@ finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
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@end table
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Some examples follow.
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@subsection Examples
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@itemize
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@item
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Set a rectangle covering the area with top left corner coordinates 0,0
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and size 100x77, setting a band of size 10:
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@ -2382,7 +2414,8 @@ video with inverted luma.
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Set the thickness of the box edge. Default value is @code{4}.
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@end table
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Some examples follow:
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@subsection Examples
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@itemize
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@item
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Draw a black box around the edge of the input image:
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@ -2680,10 +2713,7 @@ The timestamp of the current frame, in seconds, with microsecond accuracy.
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@subsection Examples
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Some examples follow.
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@itemize
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@item
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Draw "Test Text" with font FreeSerif, using the default values for the
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optional parameters.
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@ -2818,6 +2848,7 @@ Default value is 0.
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@end table
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@subsection Examples
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@itemize
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@item
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Fade in first 30 frames of video:
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@ -2931,14 +2962,20 @@ 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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@subsection Examples
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# convert the input video to any of the formats in the list
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@itemize
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@item
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Convert the input video to the format @var{yuv420p}
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@example
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format=yuv420p
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@end example
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Convert the input video to any of the formats in the list
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@example
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format=yuv420p:yuv444p:yuv410p
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@end example
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@end itemize
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@section fps
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@ -3017,7 +3054,7 @@ description), a position (specified by the syntax @var{X}/@var{Y},
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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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@subsection Examples
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@itemize
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@item
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@ -3114,7 +3151,7 @@ plane. Returns 0 if there is no such plane.
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For functions, if @var{x} and @var{y} are outside the area, the value will be
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automatically clipped to the closer edge.
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Some examples follow:
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@subsection Examples
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@itemize
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@item
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@ -3421,7 +3458,8 @@ The options can also be set using the syntax: @var{hue}:@var{saturation}
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In this case @var{hue} is expressed in degrees.
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Some examples follow:
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@subsection Examples
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@itemize
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@item
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Set the hue to 90 degrees and the saturation to 1.0:
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@ -3788,7 +3826,8 @@ The parameter syntax and behavior for the listed filters are the same
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of the corresponding MPlayer filters. For detailed instructions check
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the "VIDEO FILTERS" section in the MPlayer manual.
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Some examples follow:
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@subsection Examples
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@itemize
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@item
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Adjust gamma, brightness, contrast:
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@ -3814,15 +3853,22 @@ 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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@subsection Examples
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# convert the input video to any of the formats not contained in the list
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@itemize
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@item
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Force libavfilter to use a format different from @var{yuv420p} for the
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input to the vflip filter:
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@example
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noformat=yuv420p,vflip
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@end example
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@item
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Convert the input video to any of the formats not contained in the list:
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@example
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noformat=yuv420p:yuv444p:yuv410p
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@end example
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@end itemize
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@section noise
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@ -3869,9 +3915,10 @@ uniform noise (gaussian otherwise)
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@end table
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@end table
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Some examples follow:
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@example
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@subsection Examples
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Add temporal and uniform noise to input video:
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@example
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noise=alls=20:allf=t+u
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@end example
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@ -5288,7 +5335,8 @@ Default value is 1.0 for @option{luma_amount}, 0.0 for
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@option{chroma_amount}.
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@end table
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Some examples follow:
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@subsection Examples
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@itemize
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@item
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Apply strong luma sharpen effect:
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@ -6400,15 +6448,21 @@ other integer value between this range is allowed.
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@end table
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Example of real-time graph using @command{ffplay}, with a EBU scale meter +18:
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@subsection Examples
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@itemize
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@item
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Real-time graph using @command{ffplay}, with a EBU scale meter +18:
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@example
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ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"
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@end example
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@item
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Run an analysis with @command{ffmpeg}:
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@example
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ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -
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@end example
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@end itemize
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@section settb, asettb
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@ -6509,7 +6563,8 @@ explicitly by the user.
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Different frame rates are acceptable but will result in variable frame rate
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at output; be sure to configure the output file to handle it.
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Examples:
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@subsection Examples
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@itemize
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@item
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Concatenate an opening, an episode and an ending, all in bilingual version
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@ -6652,7 +6707,8 @@ option @var{n}. Default value is "25".
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Specify the video size for the output. Default value is "600x240".
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@end table
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Some examples follow.
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@subsection Examples
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@itemize
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@item
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Output the input file audio and the corresponding video representation
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@ -6739,7 +6795,7 @@ input -----------> deltapts0 --> overlay --> output
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movie --> scale--> deltapts1 -------+
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@end example
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Some examples follow.
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@subsection Examples
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@itemize
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@item
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