CoreAudio and external sync--fixed ?

[jnash]

I have read in several places on the DUC that CoreAudio has problems with external clock sync.

I'm using a Digi 001, so I'm not able to use the most recent ProTools or CoreAudio versions, but the problem I experience is that my UA 2192 converters sound OUTSTANDING when I sync ProTools to their clock via S/PDIF. And I get the same great sound with applications that allow selecting the Digi hardware directly from their preferences (DSP-Quattro and Live, for instance).

But, when I try to select the Digi hardware from the Sound control panel and use iTunes, QuickTime, or anything else, I get lousy sound and intermittent clicks and pops when I try to use external sync via S/PDIF.

I'm hoping that maybe this is a known bug that has been fixed, so maybe an upgrade to current Digi hardware and software would fix this problem ? Can anyone who has experienced the external sync/CoreAudio sound degradation confirm this ?

Also, does anyone understand the OS X audio layers well enough to explain the difference between selecting Digi hardware in the Sound control panel versus selecting it directly within an application that supports it ? CoreAudio is being used in both cases, right ? Is what Apple calls the Hardware Abstraction Layer the difference--i.e. it's not used by apps like Live and DSP-Quattro, but it's required by iTunes and QuickTime ? If so, then it appears the HAL is the element that doesn't work well with external clock sync...

Thanks for any advice!

James
[email protected]

[jnash]

Does anyone have any information on external clock sync with CoreAudio ? DigiTechSupport ?

I'd really appreciate it if someone could confirm whether or not there are officially-recognized bugs with CoreAudio when syncing to an external clock source (S/PDIF), and whether or not these bugs have been resolved in any of the current releases of PTLE. (I am using 001 and LE 6.4cs9 on 10.3.9, so I'm hoping the external clock sync problems I'm experiencing have possibly been resolved with the 002 and 6.9 on Tiger ?)

Thank you for any information!

James
[email protected]

[Digi Engineering]

Hi James,

I don't know of any bugs related to external sync and the CoreAudio driver, other than maybe the clock source setting not getting restored correctly when the Manager app gets launched. Could this explain your problems, maybe your setting has gotten lost and you're actually using internal sync? (If this is the case then you'd have to open the Hardware Setup dialog from the Manager app and set the clock source each time.) Let me know.

Regarding the differences between using the "Default Output" device and selecting the device directly from an app's control panel, there are no differences - the behavior should be exactly the same either way. The HAL is used in both scenarios.

digi-eng

[DigiTechSupt]

Which version of Pro Tools and the Core Audio driver are you using?

What is the sample rate you're running at? Is it possible that the application you're using and the clock source have mismatched sample rates?

[jnash]

Thank you for the suggestions, Digi! I'm afraid the problem is still at large, though...

1) Clock source setting. If I manually open the CoreAudio Manager before starting iTunes playback and select Hardware Setup, S/PDIF sync is shown to be selected. And when I return to ProTools after using CoreAudio, S/PDIF is still selected for sync, so I'm assuming that setting is active while I'm using CoreAudio as well ? But, I can't actually confirm the S/PDIF sync after iTunes connects because the Hardware Setup button in CoreAudio Manager gets greyed out. Also, if I monkey with the sample rate on my UA 2192 hardware while playing back an audio file through iTunes/CoreAudio, the playback speed/pitch changes, leading me to believe CoreAudio is indeed syncing to the S/PDIF output of the UA 2192. Does this all make sense, or is there some other way I can confirm that CoreAudio is truly set to external sync ?

2) Sample rate. I don't think there is a problem here. I'm playing back a 44.1k file from iTunes into CoreAudio, and the CoreAudio Manager shows a 44.1k connection. And my 2192 converter is set to 44.1k as well. The problem I'm experiencing is more subtle, I think, anyway. If I had a true sample rate mismatch, I'd expect to get some serious glitching. As it is, I get only one or two noticeable clicks every minute or so, and the overall sound quality through CoreAudio is subtly degraded all the time. But I'm talking about a *subtle* sonic difference between CoreAudio versus ProTools playback of the same file--if I weren't listening carefully through good monitoring equipment, I might not notice the difference, I'd only hear the occasional clicks/pops with CoreAudio.

I'm using a 001 with OS 10.3.9, ProTools 6.4cs9, and CoreAudio 6.9. Now, I know... that's not a supported configuration. The reason I'm using CoreAudio 6.9 and OS 10.3.9, however, is because I was experiencing the CoreAudio external sync problems with earlier versions of OS X and CoreAudio, and I upgraded in hopes that it might solve the external sync problem.

Also, I haven't scrutinized my particular configuration very carefully because I've read other reports of similar problems on the DUC:

lwilliam reported "flakey" behavior with CoreAudio and external sync:
http://duc.digidesign.com/showflat.p...&Number=805158

and someone logging in as DigiTechSupport confirmed the sound degradation with CoreAudio and iTunes/QuickTime:
http://duc.digidesign.com/showflat.p...&Number=853682

I've tried most if not all of the versions of OS X and CoreAudio that have been released over the past few years, but if you really think a particular configuration of OS and CoreAudio will solve my problem, I'll give it a try.

My best guess is that the CoreAudio performance with external sync is jittery--that's what it sounds like to me: subtly cloudy/grainy sound with occasional noticeable clicks/pops/glitches. But I get perfect playback when I use DSP-Quattro and select the 001 directly via the audio prefs within DSP-Quattro, so the problem seems to be related to the selection of the 001 via Appple's Sound Control Panel. I can use my 001 with external sync flawlessly with any app that has internal provisions to route to the 001 (ProTools of course does this, but I also get flawless performance with Live and DSP-Quattro). But iTunes is, from what I've seen, the best "jukebox" software out there, and I don't get the same level of audio performance from it, or from QuickTime, or from any other app I have that routes sound to the 001 via the Sound control panel.

Thank you so much for helping me work on this problem, Digi. If you know of no bugs between CoreAudio and external sync, and if it would help for me to install particular versions of ProTools, CoreAudio, and OS X, or change any system configuration settings to help try to debug this, I'm willing to do any of that. I'd certainly like to help resolve this problem, whether it affects just my system, or whether it's a widespread bug. But I have assumed it's a specific bug because my system works flawlessly with external sync and ProTools LE, DSP-Quattro, and Ableton Live... the problems only appear with QuickTime and iTunes.

Please let me know what I should try next--thanks!

James
[email protected]

[jnash]

Digi,

Could you please suggest what I should do next to try to debug this ?

Do you know for sure that the 001 has been tested with CoreAudio (iTunes or QuickTime) and external S/PDIF sync with no sound degradation and clicks/pops ? If so, could you please tell me what versions of OS X and CoreAudio were used ? 10.3.4 and CoreAudio 6.4 ?, 6.5 ? If this is a known quantity, I'm happy to try those versions.

If it were *certain* that this bug had been fixed, I would spend the money to upgrade to a 002, PT 6.9, and Tiger. But if CoreAudio/external sync was never a recognized bug with the 001, then I'm reluctant to buy new software and hardware in HOPES that the bug has been resolved, especially when there are other reports on the DUC of similar problems with 6.9/002. Can anyone confirm that the 002 handles CoreAudio (iTunes or QuickTime) and external S/PDIF sync with no sound degradation or clicks and pops ?

I am happy to do whatever you suggest to try to resolve this bug.

Thank you for the help!

James
[email protected]

[jnash]

Digi,

If you could either advise me how to try to fix this problem, or confirm that it's indeed a bug with CoreAudio and external sync, I'd really appreciate it!

Thanks!

James
[email protected]