| Re: [proaudio] Real-Time for audio playback? |
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- To: proaudio@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [proaudio] Real-Time for audio playback?
- From: Grant <emailgrant@xxxxxxxxx>
- Date: Thu, 31 Dec 2009 08:10:02 -0800
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>>> <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