jaffacake;299720 Wrote: > So does that mean that one player will play faster than the other and be > slightly different from the original source? > > Would the clock be more accurate in, for example, Transporter hardware > where owners might expect a more accurate reproduction of the source?
The crystals in SB3 are specified to within 50ppm accuracy, so if you take the worst case where one is fast by 50ppm and the other is slow by 50ppm, then you have a total drift between the two of 100ppm or 0.000100. After one hour, the faster player would be ahead by 0.000100 hours == 360 milliseconds, which is easily audible. In reality I don't think you would ever find crystals as bad as that, but it's easy to see how even at +/- 10ppm, correction for clock drift is still required. I would estimate the threshold of audibility for the casual listener to be about 50ms. As an approximate rule of thumb 1ms is equal to 1 foot at the speed of sound. Typically there is some distance between the two rooms so you would add that to the drift that is perceived. Certainly Transporter has a better clock but it is hard to estimate exactly by how much two Transporters might drift slower than two squeezeboxes. It's a manufacturing tolerance issue so you can't really characterize it without comparing LOTS of units. In any case, a design which depends on two crystals having exactly the same frequency is simply broken as this is never achievable in practice. Even two perfectly identically manufactured crystals will not behave the same in a real world setting because they will be operating at different temperatures, and this affects the speed too. I am not entirely up to speed on all of the improvements that Alan has made but my most recent understanding is that we still resync on track boundaries. This is not an unreasonable approach, but it's not ideal either because it inherently makes it impossible to do gapless playback while synced. To do that we would need to implement a gradual correction scheme where clock drift is corrected over a relatively long period of time. -- seanadams ------------------------------------------------------------------------ seanadams's Profile: http://forums.slimdevices.com/member.php?userid=3 View this thread: http://forums.slimdevices.com/showthread.php?t=47344 _______________________________________________ discuss mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/discuss
