IETF Opus codec now ready for testing
Reply #173 – 2012-07-18 06:22:43
I'm finally testing it! If I try encoding at 2kbps, VBR or CBR, at anything other than 20ms packets (I tested 10ms and 60ms), the encoder fails. And more than that, it reports a successful encode, with crazy speed like that:F:\Test\Opus\opus-tools_exp_1a50ad0b\opus-tools>opusenc --hard-cbr --bitrate 2 --framesize 60 t1.wav t1-cbr-2kbps-60ms.opus Encoding using libopus 0.9.11-119-g1a50ad0-exp_analysis (audio) ----------------------------------------------------- Input: 48kHz 2 channels Output: 2 channels (2 coupled) 60ms packets, 2kbit/sec CBR Preskip: 312 Encoding complete ----------------------------------------------------- Encoded: 29 minutes and 4.8 seconds Runtime: 0.6471 seconds (2696x real-time) Wrote: 107430 bytes, 29080 packets, 1820 pages Bitrate: 0.133333kbit/s (without overhead) Rate range: 0.133333kbit/s to 0.133333kbit/s (1 to 1 bytes per packet) Overhead: 72.9% (container+metadata) At 3kbps things already run fine with with all modes that I tested. BTW, how do I know if Opus is using the Silk or Celt mode for encoding? I don't see this info in the opusenc or opusinfo. It would be good to know, especially if it overrides your choice. I don't want to memorize a table with the heuristics/allowed combinations (even thought I may end up memorizing it). It seems that the minimum bitrate supported is indeed 6~7kbps. Even at this bitrate the voices are still very clear, and the music gets interesting analog-like noise/artifacts (better than metallic sound of most codecs close to their limits). 60ms packets are better overall at those bitrates. But if I try to force it under that with --hard-cbr it falls completely apart... That means I can't put 50 minutes of audio in a floppy, like AAC and speex could (well, AAC was also a train-wreck at 2~3kbps, but still better than opus)... One less way I can show off opus, but don't really impact in practical uses.