* wolfgang buresch <[EMAIL PROTECTED]> on Sun, 21 Oct 2001 | Q#10: "What bitrates are used?" | A:".....In LP2 and LP4 modes 20 bytes of dummy data per | 212 byte soundgroup......" --> those 20 bytes -- are they | a fact or just a wild guess?
They are a fact. The dummy data is required so that MiniDiscs recorded in LP modes will not damage older players. That is, those 20 bytes per sound group are the equivalent of "no sound" for older players instead of loud noise. That is why you get slightly less than 160 minutes in LP2 mode out of an MD-80 disc. Sony had to do it that way becuase they left no room for expansion in the MD storage algorithm. Admittedly, they never forsaw a time where anyone would want to *reduce* recording quality. | We know from ATRAC1 that it records at (exact) 292162.5 bits/sec. I could | not find an exact number for ATRAC3 (LP2) -- is it 132300? Looking at ATRAC in "bits per second" is somewhat inaccurate because it doesn't work that way. An ATRAC encoder gets a 16 bit wide block of data (Linear PCM, same as CD-DA). Standard ATRAC removes 4 bits out of every 5 from the signal resulting in a 5:1 reduction ratio. LP2 is 10:1, removing 9 out of every 10 bits. LP4 is not 20:1 bitwise reduction, but ~15:1 reduction (I would have to check for the exact figure) combined with partial stereo channel merging (joint stereo). | I also read somewhere that LP uses huffman coding (fact?) -- only on | computers or on MD decks as well? Fiction. There is no data compression in any MD ATRAC algorithm. It is strictly bitwise reduction via psychoacoustic modeling. | And last: at Q#18 this nice picture. What do they mean by | "tonal/non-tonal component decoding"? where in this picture takes the | joint stereo stuff place? any thoughts are welcome! I don't know, specifically. -- Rat <[EMAIL PROTECTED]> \ Happy Fun Ball contains a liquid core, Minion of Nathan - Nathan says Hi! \ which, if exposed due to rupture, should PGP Key: at a key server near you! \ not be touched, inhaled, or looked at. ----------------------------------------------------------------- To stop getting this list send a message containing just the word "unsubscribe" to [EMAIL PROTECTED]
