Re: Does anyone get an AudioDevice that has both input and output channels? (question is related to software play through)
Re: Does anyone get an AudioDevice that has both input and output channels? (question is related to software play through)
- Subject: Re: Does anyone get an AudioDevice that has both input and output channels? (question is related to software play through)
- From: Jeff Moore <email@hidden>
- Date: Wed, 18 Jul 2001 15:08:46 -0700
on 7/18/01 2:54 PM, Karl MacMillan <email@hidden> wrote:
>
Playing from one device to another seems likely to fail to me if those two
>
devices do not have a common clock source (which would be the case for
>
most consumer cards). This is not an issue that can be solved by
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buffering because it is likely that this cards will run at different clock
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rates entirely (although they will be close) rather than just clock
>
jitter. Do you guys have a solution to this?
Yeah, it's called Sample Rate Conversion based on incoming timing
information which is supplied in abundance by the Core Audio APIs. Audio
apps have been doing it for years. You can too. It's not that hard. I
suggest reading up on synchronization techniques in multi-rate systems in a
good DSP book.
>
Also, I hate to see the introduction of this extra buffering - this api
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looks very promising in terms of latency (and the output only tests I have
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done seem to work well) but unless 1 IOProc can deliver both input and
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output I think this will always fall behind something like ASIO.
ASIO can't magically unify two physically separate devices either.
>
So again, will the built-in audio device driver be fixed?
I say to you again, that if you really are going to do this, then it doesn't
matter since most devices don't support it anyway. You need the general
technique or you will not have this feature in your app for most audio
devices because you are not willing to do the extra work or buffer up a bit.
--
Jeff Moore
Core Audio
Apple