problem samples for WavPack lossy
Reply #27 – 2007-05-17 11:04:19
I think when looking for desasters you have to search within artificial (electronic) music. The principle of a lossless based lossy encoder essentially involves the quality of the predictor. With the bitrates you consider the prediction error is coded with roughly 4 bits of accuracy, so in order that encodings are fine the predictor has to work pretty well. It usually is the case with natural music as with this the sample-to-sample-relation is pretty well predictable. It may happen that noise isn't masked well at a rather low bitrate but when going into the upper half of the 300...400 kbps range and especially when using higher quality settings the probability for noise being audible is so low that to me it's negligible (and it's a good attitude towards lossy codecs to allow for non-annoying issues in very rare cases which is especially easy to do as these errors normally just sound like noise). If it's up to electronic music a possible solution may be to say good bye to wavPack lossy for this genre. As wavPack doesn't have a real quality control (yet?) you might consider shadowking's proposal of OptimFrog Dualstream. Quality 3 to me too provides for an astoshingly robust quality. Moreover OptimFrog's predictor seems to be more adequate for artificial music than wavPack's. Of course there's nothing wrong using a high quality mp3 setting. But more so than with wavPack where you say wavPack doesn't deserve a 450 kbps or so usage it's to me with mp3 CBR 320. mp3 is efficient at a lower bitrate and you can't expect to get an essential improvement when going from say 256 kbps to 320 kbps. Even 256 kbps is unnessary overhead most of the time. BTW the worst known problem samples for mp3 are in the electronic music genre too. pre-echo is a general problem (though the different encoders behave differently) but most of the problems known are electronically produced. Worst known sample to me is eig. Maybe you'll never want to use mp3 again if you've heard an eig mp3 version. The problem with the problem samples is that it's hard to decide on the practical implications. We all have a tendency for perfection (you have it very much, I probably have it also to a larger extent than is really sane). But I've changed my attitude pretty much within the last year. eig for instance has no real influence on my choice of encoder and setting for the mere fact that I don't listen to such a music. I'm still interested in encoders' behavior on eig but that has nothing to do with my practicing. A pre-echo sample with more practical implication (to me) is castanets. But luckily I'm not very sensitive to pre-echo, and I can easiliy abx castanets only at low bitrate which I don't use. When I was practicing abxing very intensively one day I was able to abx castanets at 256 kbps, but I had a hard time, so castanets isn't a real problem to me when considering real life listening situations. As for mp3 I personally would use quite some quality headroom, but the 250 kbps range is the maximum I would allow. mp3 doesn't deserve more. If things aren't fine at such a bitrate (which has a probability close to zero) it won't be at 320 kbps. BTW depending on bit reservoir usage strategy (restrictions on 320 kbps frames) CBR 256 can temporarily allow for a higher audio data bitrate than CBR 320. As a safeguard against rare failure of the psy model where VBR makes things worse I personally would prefer ABR (with Lame) or CBR (otherwise). My current mp3 encodings were made with FhG CBR 192 (I would have preferred 224 or 256 kbps but I would have to give away joint stereo) - anyway quality is excellent to me (problem samples of course aren't but they are acceptable). Guess you just run into worse perfection trouble again when returning to mp3. If you reconsider using transform codecs why don't you think of using AAC, Vorbis, or MPC? They are far better candidates to get at a close-to-perfection level than mp3 is. But with your demand for perfection: why don't you do it this way: Use wavPack 350...400 kbps with a high quality setting for natural music. Play around for some time with it to heavily confirm your current experience that everything is fine (hope I don't misinterpret you). Use lossless (wavPack, FLAC, TAK, Monkey, OptimFrog or whatever you like best) for any kind of electronic music.