Re: Random Delays occurring with OSX after Mountain Lion
Re: Random Delays occurring with OSX after Mountain Lion
- Subject: Re: Random Delays occurring with OSX after Mountain Lion
- From: Benjamin Federer <email@hidden>
- Date: Tue, 25 Oct 2016 19:13:45 +0200
A customer of ours reported having issues with A/V sync where the audio gradually got more and more delayed. This also happened over longer time spans like hours to days. They were monitoring over a USB audio device and tried documenting the A/V sync offset using Quicktime screen recording and Soundflower to re-route the audio output of our software to Quicktime and the USB device. The screen recording was fine, the delay was only on the USB device. I am not entirely sure which OS they were using but it probably was El Capitan, maybe Yosemite. Since we were not able to reproduce the issue I cannot say anything about buffer time stamps. However, recreating the HAL AU fixed the issue. Not ideal, of course, but better than restarting the Coreaudiod.
John, is your issue limited to any specific device class, e.g. are the built-in devices affected?
> Am 25.10.2016 um 18:16 schrieb Doug Wyatt <email@hidden>:
>
>
>> On Oct 23, 2016, at 11:48 , John Ruf <email@hidden> wrote:
>>
>> We have been experiencing very rare random delays in the audio buffers in core audio. This is occurring in our audio mixer application which runs flawlessly on Snow Leopard and Mountain Lion.
>> This problem has been noted many times by people using professional audio applications with various hardware interfaces and digitizing hardware. When running on any of the newer operating systems they will occasionally experience delays after running the application for long periods of time (sometimes hours, sometimes days). Sometimes there is also distortion in the sound. All of this is killing our reputation with customers.
>> Often it can be cured by restarting our mixer application and we have implemented a "Restart" button to very quickly bring down the whole audio chain and restart it in about 1 second. However, there are times when that will not cure it and we have customers rebooting the computer to cure it. We have seen discussions that indicate that just killing Coreaudiod (and allowing it to automatically restart) is what is necessary.
>> We have run bench tests on our system with extra diagnostic messages letting us know when the time stamps of the input and output buffers are out of sync. We have run a system for weeks continuously and then it may pop up one day and the messages indicate that the buffers are out of sync. This buffers are outside the control of our program and therefore there is nothing we can do to trace down the cause and fix it. The only thing we can do right now to preserve some of our reputation is to automatically kill and restart core audio with our "Restart" button. We are currently running an extended bench test using Sierra in the possibly vain hope that it has cured this problem, but without Apple indicating that they have worked on this defect, there's not much hope.
>> SInce this has been occurring for several years now and we do not see Apple taking any action to address this problem directlyI am appealing to this group to see how we can have Apple investigate the cause of these very infrequent random delays.
>
> Please write a Radar and be as detailed as you can about what your application observes the system doing when the bad state is detected.
>
> Thanks,
> Doug
>
>> Of course, the problem is that no one can supply a real test case that demonstrates the problem reliably since it can take hours to weeks to occur. Unless we can eliminate this random sporadic delay we may ultimately be forced to abandon Apple computers and move to another platform for our audio applications. That would be a terrible shame.
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