[FFmpeg-devel] [PATCH] libvorbis: use 0-10 range for audio quality

Justin Ruggles justin.ruggles
Thu Jan 22 01:21:14 CET 2009


Nicolas George wrote:
> Hi.
> The attached trivial patch changes the libvorbis encoder so that the range
> for the -aq option is 0-10 instead of 0-1. My reasons for this change are:
> - The native vorbis encoder uses a similar factor:
>   venc->quality = avccontext->global_quality / (float)FF_QP2LAMBDA / 10.;

I agree that the native and libvorbis encoders should be the same.

> - The command line oggenc uses the same 0-10 range.

This is a valid consideration. I chose 0.0 to 1.0 for libvorbis when I
submitted the patch for the -aq option because lavc passes the quality
setting directly to libvorbis, which uses 0.0 to 1.0.

> - The usual quality settings (3 for 112 kbps nominal, 4 for 128 kbps) are
>   not exactly possible because 0.3?118 and 0.4?118 are not integers
>   (118=FF_QP2LAMBDA); "Nominal bitrate: 127.728000 kb/s" lacks some
>   elegance.

I don't see what this has to do with your patch.


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