Re: IOAudioDevice Startup Latency
Re: IOAudioDevice Startup Latency
- Subject: Re: IOAudioDevice Startup Latency
- From: Dirk Musfeldt <email@hidden>
- Date: Thu, 12 Dec 2002 15:23:07 +0100
No, I don't think that is true.
I don't know how to measure exactly what is happening, but I have audio DMA
as well as video DMA.
The audio DMA goes into my IOAudioEngine and is output by CoreAudio and the
video DMA goes into a QuickTime vdig.
I have observed a latency between the audio output from CoreAudio and the
video output as well as between the audio output from CoreAudio and the
DAC's line out signal.
The video output and the DAC's signal are in sync so that I can't imagine
the latency being in the DMA stream.
With kind regards
Dirk Musfeldt
Meilenstein Mac OS Software
Neue Strasse 5
D-31582 Nienburg
Germany
Tel: +49 (0) 5021 91 24 44
Fax: +49 (0) 5021 91 24 45
<
http://www.meilenstein.de/>
>
Von: Jeff Moore <email@hidden>
>
Datum: Wed, 11 Dec 2002 11:24:00 -0800
>
An: CoreAudio API <email@hidden>
>
Betreff: Re: IOAudioDevice Startup Latency
>
>
So if I'm understanding what you are saying correctly, you have
>
observed a latency between when the data is bussed to your card (by DMA
>
or some other way?) and when your card's DAC's put the signal on the
>
line. If that's right, that sounds like a hardware issue with how your
>
card interfaces with the PCI bus. This is probably not the best forum
>
for your question in that case, but perhaps I'm misunderstanding?
>
>
On Wednesday, December 11, 2002, at 07:11 AM, Dirk Musfeldt wrote:
>
>
> Hi all,
>
>
>
> I have a PCI device that has audio and video output over PCI as well
>
> as a
>
> line out port.
>
>
>
> I observe an offset between the audio over PCI and the audio over the
>
> line
>
> out port. I have difficulties to measure the exact amount of the
>
> offset but
>
> I think it is about 500 msec.
>
>
>
> Of course there has to be an offset but I think it should be less than
>
> 500
>
> msec.
>
>
>
> How could I minimize the offset?
>
>
>
>
>
>
>
> With kind regards
>
>
>
> Dirk Musfeldt
>
> Meilenstein Mac OS Software
>
>
>
> Neue Strasse 5
>
> D-31582 Nienburg
>
> Germany
>
> Tel: +49 (0) 5021 91 24 44
>
> Fax: +49 (0) 5021 91 24 45
>
> <http://www.meilenstein.de/>
>
>
--
>
>
Jeff Moore
>
Core Audio
>
Apple
>
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