Re: IOAudioEngine::clipOutputSamples cannot be called
Re: IOAudioEngine::clipOutputSamples cannot be called
- Subject: Re: IOAudioEngine::clipOutputSamples cannot be called
- From: Jeff Moore <email@hidden>
- Date: Wed, 03 Dec 2008 18:01:43 -0800
Just FYI, a lot of drivers will just queue up a short DMA transfer or
whatever to kick off the time stamps by triggering the same code that
would run normally to deliver the time stamps. This is a good approach
because it will prevent any distortions in the time stamps that would
be caused by hiccups in the start-up process of the hardware. Such
distortions show up to the HAL as the difference between the first two
time stamps being very different from the differences of the time
stamps that come later.
On Dec 3, 2008, at 5:48 PM, David Tan wrote:
Hi Jeff,
Thanks for your continuous help :-)
You're right, I didn't call takeTimeStamp(). It's might be the key
point of
my issue. I'll try to setup it. But unfortunately I don't have much
experience about it, so maybe I'll bother you more posts. Thanks in
advance!
Best Regards,
David Tan,
Software Engineer,
Dextrys Co., Ltd.
-----Original Message-----
From: coreaudio-api-bounces+david.tan=email@hidden
[mailto:coreaudio-api-bounces+david.tan=email@hidden]
On
Behalf Of Jeff Moore
Sent: Wednesday, December 03, 2008 4:48 AM
To: CoreAudio-API Mailing List
Subject: Re: IOAudioEngine::clipOutputSamples cannot be called
The HAL won't actually start doing any IO with your device until it
sees the first time stamp from the driver. This could lead to a
situation where performAudioStart() has been called but there are no
subsequent calls to the kernel trap (and hence to your
clipOutputSamples() method).
Is it possible that you've set your driver up such that it isn't
dropping a time stamp in this case?
On Dec 2, 2008, at 1:58 AM, David Tan wrote:
Hi All,
Actually I'm developing a FireWire audio driver.
As my understanding, the clipOutputSamples() should be called after
the performAudioStart() be called no matter if the DCL program is
running or not.
Is that correct?
BTW, I use iTunes to play music and the progress cannot step
forwards. I think that clipOutputSamples() cannot be called explains
it. Is that correct?
Best Regards,
David Tan,
Software Engineer,
Dextrys Co., Ltd.
From: coreaudio-api-bounces+david.tan=email@hidden
[mailto:coreaudio-api-bounces+david.tan=email@hidden
] On Behalf Of David Tan
Sent: Tuesday, December 02, 2008 4:38 PM
To: CoreAudio-API Mailing List
Subject: IOAudioEngine::clipOutputSamples cannot be called
Hi Apple,
I have asked this question two weeks before and Jeff kindly gave me
some confirmation that the overridden of it is feasible.
But unfortunately I'm still blocked at this issue.
Now my question is: is it possibly caused by incorrect setup of
output IOAudioStream?
Although I can see my device on Sound Preference Pane and HALLab
device window, I'm suspicious of something incorrect in it.
BTW, my audio engine creates one input stream and one output stream
respectively.
--
Jeff Moore
Core Audio
Apple
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