Wavpack Hybrid as wav pre-processor ?
Reply #2 – 2008-05-19 09:02:01
wavPack lossy in it's current form is married to wavPack. Every lossless codec is based on a predictor scheme. It predicts the value of the next wave sample based on the knowledge of the previous samples. The prediction scheme is known by the decoder, and thus the predicted value itself need not be encoded. The prediction can't be exact of course, and the (usually small) prediction error is encoded losslessly. What wavPack lossy does is encode the prediction error only with an accuracy of a certain number of bits as the target accuracy. This way wavPack lossy makes use of the specific wavPack prediction scheme. The integration of a lossy variant into a lossless codec can have advantages for optimizing things. The separated procedure like it's done with lossyWAV however makes you independent from the final lossless codec. shadowking's remarks make me share my decision of doings things now: I don't have a huge collection, but I don't want a lossless plus a lossy production archive any more. I want just 1 productive archive. What I do is: a) as a standard procedure I use lossyWAV at a very high quality setting (-q 7.0 --shaping 0.5). b) for the rare tracks which have a very important meaning to me I use lossyWAV -q 10.0 --shaping 0.8. c) for all the tracks that can be compressed very effeciently by a lossless codec so that procedure a) resp. b) produces a larger file or a file of nearly the same size I use wavPack normal -x3 (x5 at the moment as I have tak files already so I can tell whether or not lossless coding is efficient). I also encode losslessly in those very rare cases when a track has an extremely important meaning to me. d) I also have a considerable number of mp3 files. I will continue to use mp3 at very high bitrate for the tracks that have a minor meaning and quality to me. This way I get what I want qualitywise and i feel safe for the future. For a) to c) final codecs can be exchanged, and mp3 is considered to be pretty much future safe. When the day should come for mp3 transcoding I guess it won't hurt then to transcode to lossless (or very high quality lossy without really sacrifying quality).