[Libav-user] qscale for vorbis encoder

[YIRAN LI]

Hi Guys,

I'm trying encoding ogg video with native experimental vorbis encoder.
While documentation here says the max qscale is 10 for vorbis audio, and
default is 6, http://ffmpeg.org/trac/ffmpeg/wiki/TheoraVorbisEncodingGuide

But I found that even if I pass 150 to -qscale:a I still can get files with
larger size than -qscale:10 (I keep same qscale for video, so I assume the
size increment is caused by audio part).

and the code fragment for vorbis quality is here

    avccontext->bit_rate = 0;
    if (avccontext->flags & CODEC_FLAG_QSCALE)
        venc->quality = avccontext->global_quality / (float)FF_QP2LAMBDA;
    else
        venc->quality = 8;
    venc->quality *= venc->quality;


So could anyone tell me what's the maximum value I can set
AVCodecCtx->global_quality for Vorbis encoder?

Great thanks!
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