A WAV RIFF will have in it's header a tag that indicates there is a compressor used, and maybe additional information for the compressor (called a CB or compressor block) that follows the header. There are a lot of different types of compressors it can use, you can find it in the Windows header file somewhere (mmreg.h I think?). You need a CODEC to uncode most of them. ADPCM means Adaptive Differential encoding. There is another type called Mu-Law encoding. ADPCM works by storing differences between samples that change. It doesn't lose any of the sound information. MP3 and OGG lose information (well, I think they throw it away on purpose, which is why they get better compression ratios). Once you lose that information though it is gone forever. I don't think there is any way to get it back again. You can notice it if you take an MP3 Rip and convert it to OGG. It will sound weird and you will notice that information lost forever. ----- Original Message ----- From: "Jaakko Prattala" <Jaakko.Prattala@xxxxxxxxxxx> To: <linux-audio-user@xxxxxxxxxxxxxxxxxx> Sent: Monday, March 31, 2003 10:40 PM Subject: Re: [linux-audio-user] Audio file format > On Monday 31 March 2003 13:16, Robert Epprecht wrote: > > 1.wav: RIFF (little-endian) data, WAVE audio, Microsoft ADPCM, mono 44100 > > Hz > > > > > > I thought WAVE was a format without compression? The duration of the files > > (when played by 'play') shows that this is not possible. So what is it? > > ADPCM is a kind of a compression method. > That's all (I think) I know. Google is your friend: > 92800 hits for adpcm :-) > > -- > Jaakko Prättälä > Jaakko.Prattala@xxxxxxxxxxx > >
