Patrick Dixon;325171 Wrote: > Solving the problem with a buffer is not straightforward. The read and > write clocks will never be at exactly the same frequency (and won't be > constant either), but they are at the same nominal frequency.
Consider the following scenario: suppose you have a local clock in your DAC with an adjustable frequency (such clocks exist and are used in some DACs). For simplicity we'll ignore jitter in that clock (and any other local jitter source) and worry only about jitter in the incoming S/PDIF stream. Now you record the incoming data stream in a buffer for (say) 1 second. Then you start to play out the buffer using your local clock. The analogue signal coming out is jitter-artifact free given the above assumption. But now we will run into a problem - our buffer will start to either fill or empty depending on the mismatch in average timing between the local and source clocks. But since our local clock is adjustable, we can monitor the buffer state and make a (tiny) adjustment. We'd need to do that at most every second, but in reality much less often (since the clock mismatch will be smallish). As far as I can see this scheme removes all jitter with a frequency higher than some very low cutoff (which in this example will be around 1 Hz times the fractional clock mismatch). -- opaqueice ------------------------------------------------------------------------ opaqueice's Profile: http://forums.slimdevices.com/member.php?userid=4234 View this thread: http://forums.slimdevices.com/showthread.php?t=50147 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
