[opus] Stereo dropping to mono with libopus 1.2 RC

Jean-Marc Valin jmvalin at jmvalin.ca
Sun Jun 18 13:28:30 UTC 2017

Hi Matěj,

Yes, I would be interested in the samples, both the original and the
encoded versions with 1.1 and 1.2-rc.



On 18/06/17 07:01 AM, Matěj Steklík wrote:
> Hello, I'm not a programmer or Opus developer but I tried to test the
> sound quality of a music file (Nick Warren - Devil's Elbow, freely
> available from the author's Soundcloud account) encoded with libopus 1.2
> RC1. I used Windows binaries from free-codecs.com. I noticed that in the
> case of my selected music file (which is generally harsh on lossy codecs
> as it's necessary to use quite a high bitrate to make differences
> between the original and processed file inaudible), there is a long drop
> of stereo to mono (or something which sounds similar) at the beginning
> of the track and a few others much shorter during the whole track
> lenght. The selected bitrate is 32 kb/s stereo and everything else on
> default values. This is not happenig with libopus 1.1.x. Also while
> generally the quality of sound at 32 kb/s is now better with libopus 1.2
> than before (except for those stereo to mono drops, of course), at 48
> kb/s (so probably CELT only) the quality seems slightly lower than with
> libopus 1.1.x. The difference is minimal but the sound feels a bit more
> "flat". Stereo to mono drops happens at 48 kb/s as well but they're not
> as noticeable. If you want, I can upload the encoded files somewhere so
> you can check them. I think this should be solved before the final 1.2
> release as it strongly influence the sound quality of encoded files.
> Thanks for reading.
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