[FFmpeg-devel] [PATCH 1/2] doc/encoders: Reformat libmp3lame doc

Stefano Sabatini stefasab at gmail.com
Wed Aug 28 23:59:18 CEST 2013


On date Monday 2013-08-26 16:48:19 -0700, Timothy Gu encoded:
> On Friday, August 16, 2013, Stefano Sabatini wrote:
> 
> > On date Wednesday 2013-08-14 17:51:38 -0700, Timothy Gu encoded:
> > > +
> > > +The @option{b} and @option{q} are mutually exclusive, as they
> > > +both set the quality, but refer to two different encoding modes:
> > > +CBR and VBR. The default is CBR mode (i.e. @option{b} is set).
> > > +This also applies to @option{bit_rate} and @option{global_quality}.
> >
> > This also seems a bit redundant in this specific context since it's
> > more related to the way the library works in general.
> >
> 
> So you mean that this is better off in the shared options chapter?

Ideally we could have a dedicated section explaining the
bitrate/quality parameters.

> 
> [...]
> 
> Timothy

> From 92758d06876836f084c3de33ac21e2d478d5455a Mon Sep 17 00:00:00 2001
> From: Timothy Gu <timothygu99 at gmail.com>
> Date: Sat, 3 Aug 2013 16:51:26 -0700
> Subject: [PATCH 1/2] doc/encoders: Reformat libmp3lame doc
> 
> ---
>  doc/encoders.texi | 48 +++++++++++++++++++++++++++++++-----------------
>  1 file changed, 31 insertions(+), 17 deletions(-)
> 
> diff --git a/doc/encoders.texi b/doc/encoders.texi
> index 585eae6..7690466 100644
> --- a/doc/encoders.texi
> +++ b/doc/encoders.texi
> @@ -420,26 +420,40 @@ Requires the presence of the libmp3lame headers and library during
>  configuration. You need to explicitly configure the build with
>  @code{--enable-libmp3lame}.
>  
> - at subsection Option Mapping
> + at subsection Options
>  
> -The following options are supported by the libmp3lame wrapper,
> -the LAME-equivalent options follow the FFmpeg ones.
> +The following options are supported by the libmp3lame wrapper. The
> + at command{lame}-equivalent of the options are listed in parentheses.
>  
> - at multitable @columnfractions .2 .2
> - at item FFmpeg            @tab LAME
> - at item b                 @tab b
> -Set bitrate expressed in bits/s, LAME @code{bitrate} is expressed in
> -kilobits/s.
> - at item q                 @tab V
> -Set quality setting for VBR.
> - at item compression_level @tab q
> -Set algorithm quality. Valid arguments are integers in the 0-9 range.
> - at item reservoir         @tab N.A.
> -Enable use of bit reservoir. LAME has this enabled by default.
> - at item joint_stereo      @tab -m j
> + at table @option

> + at item b (@emph{-b})
> +Set bitrate expressed in bits/s for CBR. LAME @code{bitrate} is
> +expressed in kilobits/s.

> This option is valid only using the + at command{ffmpeg} command-line
> tool.

That's not correct, this can be set via libavcodec with
av_opt_set(avctx, "b", "100k", ...); -> remove


> +
> + at item bit_rate (@emph{-b})
> +Set bitrate expressed in bits/s for CBR. LAME @code{bitrate} is
> +expressed in kilobits/s. This option is valid only using
> + at samp{libavcodec} library interface.

Please remove this part altogether, for the reasons I already
expressed (bit_rate is an AVCodecContext field, but we are only
documenting AVOption options, which are (mostly) the same for av_opt()
programmatic interface and the command line).

> +
> + at item q (@emph{-V})
> +Set constant quality setting for VBR.

=> This option is valid only using the @command{ffmpeg} command-line tool.

[...]
-- 
FFmpeg = Faithless & Fancy Maxi Patchable Energized Gargoyle


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