[FFmpeg-devel] [PATCH] libvorbis: use 0-10 range for audio quality
Nicolas George
nicolas.george
Tue Jan 20 12:00:54 CET 2009
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.;
- The command line oggenc uses the same 0-10 range.
- 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.
Regards,
--
Nicolas George
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diff --git a/libavcodec/libvorbis.c b/libavcodec/libvorbis.c
index 03c9f88..819f01c 100644
--- a/libavcodec/libvorbis.c
+++ b/libavcodec/libvorbis.c
@@ -57,7 +57,7 @@ static int oggvorbis_init_encoder(vorbis_info *vi, AVCodecContext *avccontext) {
/* variable bitrate */
if(vorbis_encode_setup_vbr(vi, avccontext->channels,
avccontext->sample_rate,
- avccontext->global_quality / (float)FF_QP2LAMBDA))
+ avccontext->global_quality / (float)FF_QP2LAMBDA / 10.0))
return -1;
} else {
/* constant bitrate */
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