Getting Total Channels of an Input Device
Getting Total Channels of an Input Device
- Subject: Getting Total Channels of an Input Device
- From: Craig Bakalian <email@hidden>
- Date: Fri, 11 Mar 2005 05:03:31 -0500
Hi,
I still have Daisy's source on my hard drive. I have realized that
the way to get the total channels of an input device is a bit more
complex than I thought. Must I do the following to get the total
channels?
UInt32 outsize;
Boolean writable;
AudioBufferList *bufferList;
UInt32 channelCount;
AudioDeviceGetPropertyInfo(inputDeviceID, 0, isInput,
kAudioDevicePropertyStreamConfiguration, &outsize, &writable);
bufferList = malloc(outsize);
AudioDeviceGetProperty(inputDeviceID, 0, isInput,
kAudioDevicePropertyStreamConfiguration, &outsize,bufferList);
for(i=0;i<bufferList->mNumberBuffers:i++)
{
channelCount += bufferList->mBuffers[i].mNumberChannels;
}
Am I correct in assuming that if a device has a
kAudioDevicePropertyStreamConfiguration with a bufferList count of 2,
and each buffer has a channel count of 2 that there is 4 channels in
the input device? And, another example could be a bufferList count of
2 where each buffer has 1 channel, does this mean the input device has
2 channels of audio data? Is that configuration possible? Are there
any impossiblities?
I apologize for my ignorance, I am just trying to get a handle on the
paradigm of BufferList, mBuffers[], mData Is it safe to say, a
BufferList may contain many mBuffers, and a mBuffer may contain one
mData. And the confusion for me is the state of mData. Is mData laid
out according to the AudioStreamBasicDescription's mChannelsPerFrame,
thereby mData may contain many channels of audioData.
Isn't this a bit obfuscated? Do audio engineers really need to go this
far? Does audio recording really need this much complexity? Wouldn't
the data coming into a IOProcess be a bit more intelligent if was a
list of channels instead of a list of channels with channels? Or am I
simply confused? Help, please someone open this conversation, reply,
please reply!
Craig Bakalian
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