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documentation: add setdar and setsar description to filters.texi

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Stefano Sabatini 2011-03-26 16:14:15 +01:00
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doc/filters.texi
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@ -1001,6 +1001,36 @@ ratio of the input image.
The default value of @var{width} and @var{height} is 0.
@anchor{setdar}
@section setdar
Set the Display Aspect Ratio for the filter output video.
This is done by changing the specified Sample (aka Pixel) Aspect
Ratio, according to the following equation:
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
Keep in mind that this filter does not modify the pixel dimensions of
the video frame. Also the display aspect ratio set by this filter may
be changed by later filters in the filterchain, e.g. in case of
scaling or if another "setdar" or a "setsar" filter is applied.
The filter accepts a parameter string which represents the wanted
display aspect ratio.
The parameter can be a floating point number string, or an expression
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
numerator and denominator of the aspect ratio.
If the parameter is not specified, it is assumed the value "0:1".
For example to change the display aspect ratio to 16:9, specify:
@example
setdar=16:9
# the above is equivalent to
setdar=1.77777
@end example
See also the "setsar" filter documentation (@pxref{setsar}).
@section setpts
Change the PTS (presentation timestamp) of the input video frames.
@ -1061,6 +1091,32 @@ setpts=N/(25*TB)
setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
@end example
@anchor{setsar}
@section setsar
Set the Sample (aka Pixel) Aspect Ratio for the filter output video.
Note that as a consequence of the application of this filter, the
output display aspect ratio will change according to the following
equation:
@math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
Keep in mind that the sample aspect ratio set by this filter may be
changed by later filters in the filterchain, e.g. if another "setsar"
or a "setdar" filter is applied.
The filter accepts a parameter string which represents the wanted
sample aspect ratio.
The parameter can be a floating point number string, or an expression
of the form @var{num}:@var{den}, where @var{num} and @var{den} are the
numerator and denominator of the aspect ratio.
If the parameter is not specified, it is assumed the value "0:1".
For example to change the sample aspect ratio to 10:11, specify:
@example
setsar=10:11
@end example
@section settb
Set the timebase to use for the output frames timestamps.