site_archiver@lists.apple.com Delivered-To: darwin-dev@lists.apple.com So far I've figured out the following; please correct me If I'm wrong: Please help Rich _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... Im working on the pure darwin system and am trying to get audio working. As the open-source Apple components include all kernel components but not userspace (CoreAudio), I'm attempting to write an application which reads audio from an input device and saves it into a file. Unfortunately I'm having problems - at least in part related to the lack of documentation; writing a kernel driver is documented as is CoreAudio but not the userspace/kernelspace interface. * I can access the IOAudioEngineStatus for a IOAudioEngine (via the IOAudioEngineUserClient) by calling IOConnectMapMemory with kIOAudioStatusBuffer. Q. Is there a mechanism to tell me when its safe to use this data, or is it, as I suspect, volatile and you use it "as it". * IOConnectMapMemory with kIOAudioBytesInInputBuffer or kIOAudioBytesInOutputBuffer do nothing. Tracing through the kernel code it appears to returns a valid buffer but nothign ever writes into it (this matches with what I've seen). * To get the data for a stream I call IOConnectCallMethod with kIOAudioEngineCallRegisterClientBuffer, supplying a userspace buffer, an arbitrary bufferSetID and a streamID. This is of type IOAudioBufferDataDescriptor (+ lots of buffer space). * Calling IOConnectCallMethod with kIOAudioEngineCallStart/ kIOAudioEngineCallStop starts/stops the engine (respectively) So based on this and the fact that input is simpler than output (according to the audio kernel documentation) I'm trying to record. So I'm creating a buffer, registering it, starting the engine, setting the fActualNumSampleFrames member of my buffer to 256 and then calling IOConnectTrap6 with kIOAudioEngineTrapPerformClientIO. This appears to give me data but just not intelligible stuff. I was expecting IOConnectTrap6 with kIOAudioEngineTrapPerformClientIO to block for ~0.005 seconds (time taken to read 256 sample frames) but it doesn't. Q. My key question is how do I get intelligible audio from the driver? I've tried putting a sleep in, but to no avail. Also I was expecting that if I called IOConnectTrap6 with kIOAudioEngineTrapPerformClientIO repeatedly but incremented firstSampleFrame by 256 each time I'd see the driver write data into the first 2048 bytes of fData, the first time, then the next 2048 bytes etc etc i.e. start writing into the fData buffer at firstSampleFrame's * sizeof( float ) * numchannels in ... again it doesn't and appears to simply overwite the first 2048 bytes of fData. I've tried many things but still can't get it to work so any help or pointers you can provide will be greatfully recieved. This email sent to site_archiver@lists.apple.com