Re: CAPlayThrough sample code problem
Re: CAPlayThrough sample code problem
- Subject: Re: CAPlayThrough sample code problem
- From: tahome izwah <email@hidden>
- Date: Thu, 05 Jan 2012 14:42:43 +0100
CAPlayThrough never worked correctly, I have mentioned this many times
(and got into a little bit of a fight with the Apple engineers a while
ago). The reason seems to be that their varispeed AU loses precision
after some time and eventually goes out of sync. This causes drop-outs
after some 30+ minutes of uptime. After implementing my own varispeed
algorithm using code from www.dspdimension.com I finally got it to
work and it's working great to this date.
HTH
--th
2012/1/5 Heinrich Fink <email@hidden>:
> Hi Daniel,
>
> I have also recently spent some time with the CAPlayThrough example, although I haven’t tested it running for a longer time than just a couple of seconds. It’s certainly interesting to try syncing multiple devices on your own, but it’s also a considerably hard and, for most scenarios, an unnecessary task. I would strongly recommend you to use "Aggregate Devices” instead, which take care of the syncing for you:
>
> http://developer.apple.com/library/mac/documentation/MusicAudio/Conceptual/CoreAudioOverview/ARoadmaptoCommonTasks/ARoadmaptoCommonTasks.html#//apple_ref/doc/uid/TP40003577-CH6-SW14
>
> You can create them via the “Audio Midi Setup” Utility App. You can also create them programmatically. I haven’t tried it myself, but I recently ran over this blog entry which might be useful to you:
>
> http://www.thismuchiknow.co.uk/?p=51
>
> The net effect of using Aggregate Devices is that you can use a single AUHal instance in your AUGraph for I/O, which really simplifies your setup.
>
> best regards,
>
> Heinrich
>
> p.s.: Since you are new to CoreAudio: Have you already tried the utility apps “HALLab” and “AULab” which come with the developer tools for testing? You could create an aggregate device, configure it, and test playthrough without writing a single line of code…
>
> On Jan 5, 2012, at 09:57 , Daniel Tapie wrote:
>
>> I have noticed a lot of audio artifacts after about 3-4 minutes of running the CAPlayThrough sample application using my DisplayAudio input (Thunderbolt 27" display) and the headphones output of my MacBook Pro (two different devices then). The sound becomes distorted after 3-4 minutes and then finally stops completely.
>>
>> I have also tried with another external USB source and it is the same problem.
>>
>> Could this be a problem in the varispeed usage in the sample ? Has anybody else seen this problem ?
>>
>> Thanks,
>>
>>
>> Daniel Tapie
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