Measuring/ranking lossy difference from input+implications for quality
Reply #1 – 2012-06-21 09:16:21
I'm of the mind that a SNR of 130 dB could be described as "better" than 120 dB, even though I'm confident human beings would be unable to tell. A single metric, which might not even be correlated well if at all with perceived audio quality is never a good thing. Look at video codec development, where some people heavily rely (relied?) on the PSNR metric . Encoders mainly optimized for that metric can fail spectacularly in real world perception tests. Noise level is certainly not the only determining factor, not in audio and not in video.Granted some sorts of distortions and artifacts are more annoying (if discernable) than others, and weighting this regarding where the ear is most sensitive (say around 3.5 kHz) makes sense to me, but I still think an automated system with absolute numbers we can compare, instead of "Go ABX your entire 500 GB music collection your self to see what the answer is" would help this person out. While I try to adhere to the ToS here at this forum, I can accept the possibility of a metric with high correlation with perceived audio quality to be useful, but so far I haven't seen one in the audio world. Also, ABX tests are not as involved as you suggest, just take a small sample of music you listen to, encode it, and conduct the tests. If you don't have enough time, even a single song might be enough. There is also no reason to go OCD over your codec choice, if you find a music piece which doesn't encode well, just turn up the quality dial a bit on your encoder, and see if it helps. It is also no problem to just choose a "overcompensating" higher encoding setting overall, if you don't want to test a lot, but keep in mind that this is wasteful and not a real solution . Transparency of lossy encoder setting results is inherently subjective, there is no objective perfect setting for every person. You can never be sure that a certain encode is transparent to everyone. That's the reason why we tell everyone to just ABX themselves. And that's the point why selling lossy audio is a bad concept to begin with, too.