SoftwireEngineer;146318 Wrote: > I guess, the buffer, is really small to makeup for time needed to > (re)read the data properly. > Except for portable players with "anti-skip" buffers, CD players do not re-read. If there is an uncorrectable error, then it is concealed, either by interpolation or in extreme cases muting. (I should just point out that the number of uncorrectable errors experienced when playing a CD in good condition on a player that's working properly is typically zero - you might get the odd one here and there on some discs, but it's not a big issue).
SoftwireEngineer;146318 Wrote: > So for all practical purposes, the 'small buffer' in the CD players > might as well be non-existent. A CD player without such a buffer simply wouldn't work, so it could not be non-existent. I think there's a danger that some people are interpreting the purpose of this small buffer in CD players as some sort of jitter-reducer. That is not its primary purpose. The data that is on a physical CD isn't a one-to-one representation of the 16 bit samples. Every 8 bits are encoded into 14 bits (so that there can never be more than 3 consecutive bits that are the same - this is to help keep the laser tracking correctly). Also, the data is arranged into blocks (588 samples, plus their error correction code, per block), and the content of a block is interleaved around the disc so that burst errors can be corrected. Thus the data stream that emerges from the laser bears little relationship to the required 16 bit samples. The buffer is used to de-interleave, decode the 8-to-14 modulation, and apply error correction where necessary. Once reconstructed, the samples are then clocked out under the control of the DAC's master clock. As it happens, because the output of the buffer is controlled by the DAC's clock, jitter from the transport is eliminated. Basically, jitter 'twixt transport and DAC is a non-issue in a single box CD player. It only rears its ugly head when you send the digital samples on to an external DAC. -- cliveb Performers -> dozens of mixers and effects -> clipped/hypercompressed mastering -> you think a few extra ps of jitter matters? ------------------------------------------------------------------------ cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=28621 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
