Re: Audio buffers in user-land audio driver
Re: Audio buffers in user-land audio driver
- Subject: Re: Audio buffers in user-land audio driver
- From: Jeff Moore <email@hidden>
- Date: Fri, 21 Mar 2008 14:07:57 -0700
The SampleHardwarePlugIn code supports multiple IOProcs where each IOProc has it's own set of output buffers. So to access the output buffers after they have been filled by the IOProcs, you need to iterate through the IOProcs in mIOProcList using HP_IOProcList::GetNumberIOProcs() and HP_IOProcList::GetIOProcByIndex() and retrieve the buffers individually for each IOProc for processing using HP_IOProc::GetAudioBufferList().
That said, you can also achieve this by doing the work in the SHP_Device::PreProcessOutputData() method. This method is called as soon as the IOProc in question returns, so you'll see the data for each IOProc one at a time as opposed to getting them all at once in the SHP_Device:: WriteOututData() method.
On Mar 21, 2008, at 1:56 PM, Dave Addey wrote: First up, many thanks to Jeff for the SampleHardwarePlugin example code. Like others on this list recently, I’m looking to create a device driver based on the example code. It’s making a lot of sense, but in trying to use it I think I’m missing something fairly fundamental about how the audio buffers are stored and passed around.
I’m not too familiar with IOProc operations, and I can’t see how I might access the contents of the output audio buffer in the WriteOutputData stage of the IO cycle defined in CallIOProcs. Is this the correct stage to be doing so, and if so, how would I retrieve the buffer? Apologies if this is a dumb question, but since the sample code obviously doesn’t do anything at this stage, I’m a little stumped.
--
Jeff Moore
Core Audio
Apple
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