• Open Menu Close Menu
  • Apple
  • Shopping Bag
  • Apple
  • Mac
  • iPad
  • iPhone
  • Watch
  • TV
  • Music
  • Support
  • Search apple.com
  • Shopping Bag

Lists

Open Menu Close Menu
  • Terms and Conditions
  • Lists hosted on this site
  • Email the Postmaster
  • Tips for posting to public mailing lists
coreaudio usb driver
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

coreaudio usb driver


  • Subject: coreaudio usb driver
  • From: Eugene Gavrilov <email@hidden>
  • Date: Mon, 1 Dec 2008 23:10:04 +0300

Hello,

I'm developing a driver for Mac OS X for USB 2.0 and 1.1 devices (which are not class-compliant).

I noticed that sometimes IOAudioEngine::clipOutputSamples() function sends a request with 'numSampleFrames' = 0. Is this correct? Why can this happen? Can this influence driver performance or indicate any problems with the timestamps? I'm also getting resetClipPosition() notification - but I don't know whether I need to deal with it or not.

Original "Apple USB Audio Driver" has a set of very complicated timestamp calculation algorithms with separate anchored time stamp timers and jitter filters.. Is there a way to implement it in a less- complex way?
My audio driver works quite fine, even with very small buffer sizes (32, 64 samples), but I'm experiencing problems with certain 3-rd party software, such as 'Cubase LE': there are occasional clicks and "click storms", especially right after sampling rate change - and in some cases the application can not recover automatically - even after a number of manual resets. (But my driver + Apple aggregated driver + Cubase work fine, without problems).
I suspect the problem is with synchronous start-up of the two audio engines (playback and recording), as they are implemented independent in my driver (similar to Apple USB Audio Driver), but I don't know where to dig into..


Is there a way to check the timestamps calculated by the driver? I tried "HALLab" application, but it does not show any problems with the timestamps: they seem to be reported accurately, "Late" field is always less than 0.1 ms. Is there any documentation on HALLab available?

I would appreciate any help on this topic, thank you in advance!

Regards,
  Eugene Gavrilov
  Senior Software Engineer,
  CEntrance, Inc.

_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden


  • Follow-Ups:
    • Re: coreaudio usb driver
      • From: Jeff Moore <email@hidden>
  • Prev by Date: kAudioFilePropertyAudioDataByteCount?
  • Next by Date: Re: kAudioFilePropertyAudioDataByteCount?
  • Previous by thread: Re: kAudioFilePropertyAudioDataByteCount?
  • Next by thread: Re: coreaudio usb driver
  • Index(es):
    • Date
    • Thread