lossyWAV noise questions
Reply #5 – 2010-04-21 20:43:59
With a former implementation there was a sample for which -P was considered non-transparent. After that the --altpreset (aka -t) option was introduced which made things more defensive for qualtiy levels below -S as a tendency while keeping bitrate more or less the same. I don't remember the exact details but some suspicion came up that -P -t isn't transparent too (which made me increase the quality level for productive purposes - paranoid me). So if you have a sample you can ABX with -P -t it would be welcome to know (though we certainly prefer that there isn't such a thing). A more intelligent noise shaping targeting at lower bitrate is a bit problematic. At the moment things are pretty much free of flaws - with the only open question whether or not exactly -q 2.5 -t can be considered transparent (we do know though that this is a very good setting quality-wise, and paranoid people like me can go just a bit higher - saving some kbps isn't so important any more nowadays). Targeting at 320 kbps or so probably means we have to give up confidence in quality. More or less the same like with mp3 etc. Look at wavPack lossy which is an alternative to lossyWAV in case you don't have problems playing it back. wavPack lossy has a more effecient noise shaping which together with its integration into just one procdure allows for very good quality usually at around 300 kbps. But it comes at the price that you can't be sure that noise shaping works sufficiently well. It usually does, but that's all. To me it's more consequent not to do noise shaping (or maybe a simple defensive noise shaping towards very high frequencies which however has disadvantages when transcoding to mp3 etc.). It's simply more fail-safe which matches the properties of lossyWAV. For practice moreover in case you are willing to spend more kbps than usually done witn mp3 etc. for the sake of quality, it's not so important nowadays whether it's 320 kbps or 380 kbps. The 60 kbps saving doesn't come for free.