Codecs and settings for 64kbit/s SE listening test, criticism required Options

[Serge Smirnoff]

As SoundExpert now has pretty stable flow of volunteer testers it is time to update codecs in all bitrate sections. After a short discussion at Russian bit-torrent tracker we decided to update 64-96-128-192-256-320 sections first. For the 64kbit/s section five codecs were chosen:

Fhg AAC (2012-06-24) - 59.2 kbit/s (fhgaacenc --vbr 2 se_ref.wav)
QAAC TVBR (v1.42) - 59.6 kbit/s (qaac --he -v56 se_ref.wav)
Nero AAC (v1.5.4.0) - 60.1 kbit/s (neroAacEnc.exe -q 0.25 -if se_ref.wav -of out.mp4)
Vorbis (Xiph 1.3.3) - 60.3 kbit/s (oggenc2.exe -q-0.3 se_ref.wav)
Opus (libopus 1.0.1) - 59.9 kbit/s (opusenc --bitrate 59 se_ref48.wav out.opus)
Conversion chain for Opus: 44.1/16 -->> 48/24(Audition CS6) -->> opusenc -->> foobar2000(48/24) -->> 44.1/16(Audition CS6)

Bitrates are calculated on the basis of nine SE test samples concatenated. Fortunately first two codecs have close values of resulting bitrates at their corresponding discrete quality settings. Other contenders were adjusted to have close values.

Did we miss something?

[jensend]

Conversion chain for Opus: 44.1/16 -->> 48/24(Audition CS6) -->> opusenc -->> foobar2000(48/24) -->> 44.1/16(Audition CS6)

Why on earth would you do that? You should just use opusenc and opusdec. opusenc will happily accept your 44.1/16 input and running the result through opusdec will by default give you 44.1/16 output.

opusenc and opusdec will handle any resampling internally and transparently, even making sure that opusdec's output has the exact same number of samples as the input to opusenc had. Using a convoluted Audition/foobar/Audition toolchain is more likely to introduce extraneous problems.

Also, I agree with other posters that your bitrate setting selections for these codecs seems rather odd. In concluding that these are the rates that "really" give an average 64kbps output, have you really tried this with a large and diverse collection, or are you jumping to conclusions based on a few choice files? If the latter, you may well be unjustly penalizing codecs that have better VBR rate control.