2019-02-08 6:08 GMT+01:00, Gyan <ffm...@gyani.pro>: > > > On 08-02-2019 03:31 AM, Carl Eugen Hoyos wrote: >> . >> No strong opinion here, I hadn't realized that -crf 0 only works with >> newer versions. >> >> Can you explain why crf alone has no effect and needs -b:v 0? >> Isn't this a bug both with libvpx and libaom? >> > > With crf present but VBV params absent, VPX operates using a constrained > Q RC mode , where the target bitrate acts as a ceiling. Since acvodec > has a non-zero default -b of 200 kbps, this produces undesirable > effects. If set to 0, VPX switches to constant quality.
Yes. This looks like a bug to me. > I do see this block though, > > if (avctx->codec_id == AV_CODEC_ID_VP9 && ctx->lossless == 1) { > enccfg.rc_min_quantizer = > enccfg.rc_max_quantizer = 0; > } else { > if (avctx->qmin >= 0) > enccfg.rc_min_quantizer = avctx->qmin; > if (avctx->qmax >= 0) > enccfg.rc_max_quantizer = avctx->qmax; > } > > > Looks like the quantizer range is disabled only by using the deprecated > option, or has this changed? Is your question "Isn't 'lossless 1' necessary for lossless encoding"? > Also, with libvpx v1.7.0-1758, I get different results for -crf 0 -b:v > 0 vs only -lossless 1, with the latter producing a slightly larger > file, and its result showing a slightly larger SSIM score. Although > neither produces a SSIM of 1, like libx264. Not truly lossless? Please provide your input sample. Carl Eugen _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel