[FFmpeg-devel] [PATCH] doc/ffmpeg: update and extend documentation for -copytb

[Michael Niedermayer]

On Sun, Mar 25, 2012 at 11:56:12AM +0200, Stefano Sabatini wrote:
> On date Sunday 2012-03-25 02:04:48 +1030, Rodney Baker encoded:
> > On Sun, 25 Mar 2012 01:52:28 Stefano Sabatini wrote:
> [...]
> > > +If positive, the output time base is copied unchanged from the
> > > +corresponding input stream. A positive value is sometimes required for
> > > +avoiding non monotonically increasing timestamps when copying video
> > > +streams with variable frame rate.
> > > +
> > > +If zero, changes the time base as required in case the output supports
> > > +variable frame rate.
> > > +
> > > +If negative, changes the time base as with @code{-copytb 0} but only
> > > +when it seems required for generating sane output files.
> > > +
> > > +Default value is -1.
> > > +
> > 
> > So, what are the legal values? -1,0,1? Does specifying a positive integer >1 
> > cause any different behaviour than 1? If not, why not specify "if 1" rather 
> > than "if positive" to avoid ambiguity?
> > 
> > As a user who is not a developer or an expert, one thing I find very valuable 
> > in documentation is a clear articulation of what are acceptable values or 
> > ranges of values when required for specific parameters and just what they 
> > mean. 
> 
> Updated taking into consideration your feedback, thanks.
> -- 
> FFmpeg = Formidable & Furious Marvellous Problematic Elastic Glue

>  doc/ffmpeg.texi |   24 ++++++++++++++++++++++--
>  ffmpeg.c        |    2 +-
>  2 files changed, 23 insertions(+), 3 deletions(-)
> 6a9e42ae2f379390b241f2830330fde4689dd0cb  0001-doc-ffmpeg-update-and-extend-documentation-for-copyt.patch
> From 734a3d986c4f8833abe26df421680eaf59d87593 Mon Sep 17 00:00:00 2001
> From: Stefano Sabatini <stefasab at gmail.com>
> Date: Sat, 24 Mar 2012 16:11:46 +0100
> Subject: [PATCH] doc/ffmpeg: update and extend documentation for -copytb
> 
> Address trac ticket #1120.
> ---
>  doc/ffmpeg.texi |   24 ++++++++++++++++++++++--
>  ffmpeg.c        |    2 +-
>  2 files changed, 23 insertions(+), 3 deletions(-)
> 
> diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
> index 402a4ae..b32f735 100644
> --- a/doc/ffmpeg.texi
> +++ b/doc/ffmpeg.texi
> @@ -765,8 +765,28 @@ the parameter is the maximum samples per second by which the audio is changed.
>  without any later correction.
>  @item -copyts
>  Copy timestamps from input to output.
> - at item -copytb
> -Copy input stream time base from input to output when stream copying.
> + at item -copytb @var{mode}
> +Specify how to set the timebase when stream copying. @var{mode} is an
> +integer numeric value, and it can assume one of the following values:
> +
> + at table @option
> + at item 1
> +The output time base is copied unchanged from the corresponding input
> +stream. This is sometimes required to avoid non monotonically
> +increasing timestamps when copying video streams with variable frame
> +rate.
> +
> + at item 0
> +The output time base is changed as required in case the output
> +supports variable frame rate.
> +
> + at item -1
> +The output time base is changed as with @code{-copytb 0}, but only when
> +it seems required to generate sane output files.
> + at end table
> +
> +Default value is -1.

The idea behind the values is:

1
use the demuxer timbase

0
use the codec timebase

-1
try to make the choice automatically

your description describes a orthogonal aspect, maybe they can be
combined ?

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Good people do not need laws to tell them to act responsibly, while bad
people will find a way around the laws. -- Plato
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