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Re: Timing & Callbacks
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Re: Timing & Callbacks


  • Subject: Re: Timing & Callbacks
  • From: Jeff Moore <email@hidden>
  • Date: Mon, 24 Feb 2003 10:57:29 -0800

The HAL provides enough timing information about the devices in question that it is possible to judge how much faster or slower device A is going than Device B. This is known by tracking the relationship each device's sample time has with host time. Armed with this information, you can make decisions about the amount of rate conversion you do to make up for the missing samples.

Or, you could buffer the input more at the cost of latency.

In your specific case, you might want to check out our PlayEffect sample code. It does through processing, but makes use of AudioDeviceRead so as to not need an IOProc for it's input.

On Monday, February 24, 2003, at 12:34 PM, Lubor Prikryl wrote:

Hi,
if I select two different devices in my audio application, there are clicks appearing in certain periods, about 10s. The application is a realtime effect processor passing audio from input thru effect to output.

Thinking about principles of input and output callbacks, if we have two different devices, the clock is never so accurate to make the count of input and output calls to be the same, and it causes these clicks. This will not occur in one driver/multiple card solutions, where the timing may be synchronized in driver, but I am searching for a general solution.

Is it possible to solve this problem by means of CA API?

Lubor, DSound

--

Jeff Moore
Core Audio
Apple
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References: 
 >Timing & Callbacks (From: Lubor Prikryl <email@hidden>)

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