>>> <SNIP> >> How would you configure a system for the absolute lowest jitter for >> audio playback? Maybe nothing can be done besides choosing a >> low-jitter sound card and a playback app which uses a large buffer? >> > > You've got it right. Good quality equipment is where you start. Using > Jack allows you to monitor whether the buffers ever run dry. Smaller > buffers equate to lower latency but have nothing to do with jitter. If > I was going to purchase hardware I would look for two main > characteristics in semi-pro and above solutions: > > 1) DAC external to the PC - keeps internal PC electrical noise from > effecting the D/A conversion. Technically your USB device meets this > requirement. > > 2) Sound cards with a clock input - they all have crystals, but if you > can drive the device with a Word Clock or ADAT clock you can get much > lower jitter - basically as good as you want to pay for. Check out RME > cards for some great solutions in this area, but also ProSonus and > lots of other studio level companies now have semi-pro/consumer > devices that have these features. > > Of course, getting the best possible D/A chip inside your device helps also... > > One other thing you might want to explore as you investigate the > rt-sources kernel is that *disk* latency can actually be worse unless > you grant your audio driver higher priority than default. For > recording I use 1394 audio drives, not because they are faster (they > are) but because I know that the only data on them is audio and they > have their own driver in the Linux stack. I can grant the 1394 driver > higher RT priority and know that it will have no effect on system > operation in general. That way things like swap space access (yuck...) > and cron jobs, etc., don't get in the way of me moving data on and off > disk.
Can there exist small time inconsistencies (latencies?) throughout the streaming of the buffer to the USB DAC? I'm just trying to root out any possibilities for improvement in Linux as a digital audio player. Even the choice of USB cable is said to make an audible difference. This type of thing can descend into paranoia pretty easily, but I want to press on. - Grant
