Samples are helpful, also— can you try the non-experimental encoder (see http://www.opus-codec.org/downloads/ ) and see if its obviously better?
Sample: http://www.hydrogenaudio.org/forums/index....showtopic=96497
Using Headphones (Beyerdynamic DT 880):
Original vs. non-experimental (libopus 0.9.11-134-gda3b5f7): ABX 16/16 (felt significantly harder than this noon on my PC speakers)
experimental vs. non-experimental: ABX failed
Using PC speakers again (Teufel Concept E Magnum):
experimental vs. non-experimental: ABX 16/16 relatively easy. Non-experimental is clearly better.
Bitrates for the complete track (target bitrate 64 kbps):
NonExp: 62 kbps
Exp: 54 kbps
I would have expected the artifact to be blatantly obvious on headphones, but the opposite was the case. This was a first for me.
Orig vs. NonExp on headphones
foo_abx 1.3.4 report
foobar2000 v1.1.14 beta 3
2012/08/14 20:01:15
File A: F:\tmp\soundcheck\Electronica\Pendulum - Slam (incl intro).flac
File B: F:\tmp\soundcheck\Electronica\Pendulum - Slam (incl intro)_NonExp.opus
20:01:15 : Test started.
20:01:50 : 01/01 50.0%
20:01:55 : 02/02 25.0%
20:02:02 : 03/03 12.5%
20:02:54 : 04/04 6.3%
20:03:14 : 05/05 3.1%
20:03:25 : 06/06 1.6%
20:04:01 : 07/07 0.8%
20:04:23 : 08/08 0.4%
20:04:44 : 09/09 0.2%
20:04:59 : 10/10 0.1%
20:05:21 : 11/11 0.0%
20:05:33 : 12/12 0.0%
20:06:15 : 13/13 0.0%
20:06:34 : 14/14 0.0%
20:08:13 : 15/15 0.0%
20:08:20 : 16/16 0.0%
20:08:22 : Test finished.
----------
Total: 16/16 (0.0%)
Exp vs. NonExp on PC speakers
foo_abx 1.3.4 report
foobar2000 v1.1.14 beta 3
2012/08/14 20:46:39
File A: E:\tmp\Pendulum - Slam (excerpt)_Exp.opus
File B: E:\tmp\Pendulum - Slam (excerpt)_NonExp.opus
20:46:39 : Test started.
20:47:21 : 01/01 50.0%
20:47:34 : 02/02 25.0%
20:47:45 : 03/03 12.5%
20:48:04 : 04/04 6.3%
20:48:14 : 05/05 3.1%
20:48:36 : 06/06 1.6%
20:49:22 : 07/07 0.8%
20:49:41 : 08/08 0.4%
20:49:58 : 09/09 0.2%
20:50:05 : 10/10 0.1%
20:50:12 : 11/11 0.0%
20:50:30 : 12/12 0.0%
20:50:43 : 13/13 0.0%
20:51:02 : 14/14 0.0%
20:51:38 : 15/15 0.0%
20:51:45 : 16/16 0.0%
20:51:48 : Test finished.
----------
Total: 16/16 (0.0%)