问题
I have red a lot of interesting stuff today about iOS & Audio Units and have found a lot of usefull resources (SO included).
First of all, i am confused with something : Is it really necessary to create an audio graph with mixer unit to record sounds played by an app ?
Or is it sufficient to play sounds with ObjectAL (or more simply AVAudioPlayer calls) and create a single remote io unit adressed on the correct bus with a recording callback ?
Second, a more programmatically issue ! As i'm not already comfortable with Audio Units concepts, i try to adapt the apple Mixer Host project with the ability to record the resulting mix. Obviously, i try to do this with the Michael Tyson RemoteIO post.
And I get a EXC_BAD_ACCESS on my callback function :
static OSStatus recordingCallback (void *inRefCon,
AudioUnitRenderActionFlags *ioActionFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList *ioData) {
AudioBufferList *bufferList; // <- Fill this up with buffers (you will want to malloc it, as it's a dynamic-length list)
EffectState *effectState = (EffectState *)inRefCon;
AudioUnit rioUnit = effectState->rioUnit;
OSStatus status;
// BELOW I GET THE ERROR
status = AudioUnitRender(rioUnit,
ioActionFlags,
inTimeStamp,
inBusNumber,
inNumberFrames,
bufferList);
if (noErr != status) { NSLog(@"AudioUnitRender error"); return noErr;}
// Now, we have the samples we just read sitting in buffers in bufferList
//ExtAudioFileWriteAsync(effectState->audioFileRef, inNumberFrames, bufferList);
return noErr;
}
Before using the callback function i did in MixerHostAudio.h
typedef struct {
AudioUnit rioUnit;
ExtAudioFileRef audioFileRef;
} EffectState;
And create in the interface :
AudioUnit iOUnit;
EffectState effectState;
AudioStreamBasicDescription iOStreamFormat;
...
@property AudioUnit iOUnit;
@property (readwrite) AudioStreamBasicDescription iOStreamFormat;
Then in the implementation file MixerHostAudio.h :
#define kOutputBus 0
#define kInputBus 1
...
@synthesize iOUnit; // the Remote IO unit
...
result = AUGraphNodeInfo (
processingGraph,
iONode,
NULL,
&iOUnit
);
if (noErr != result) {[self printErrorMessage: @"AUGraphNodeInfo" withStatus: result]; return;}
// Enable IO for recording
UInt32 flag = 1;
result = AudioUnitSetProperty(iOUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Input,
kInputBus,
&flag,
sizeof(flag));
if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty" withStatus: result]; return;}
// Describe format
iOStreamFormat.mSampleRate = 44100.00;
iOStreamFormat.mFormatID = kAudioFormatLinearPCM;
iOStreamFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
iOStreamFormat.mFramesPerPacket = 1;
iOStreamFormat.mChannelsPerFrame = 1;
iOStreamFormat.mBitsPerChannel = 16;
iOStreamFormat.mBytesPerPacket = 2;
iOStreamFormat.mBytesPerFrame = 2;
// Apply format
result = AudioUnitSetProperty(iOUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
kInputBus,
&iOStreamFormat,
sizeof(iOStreamFormat));
if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty" withStatus: result]; return;}
result = AudioUnitSetProperty(iOUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Input,
kOutputBus,
&iOStreamFormat,
sizeof(iOStreamFormat));
if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty" withStatus: result]; return;}
effectState.rioUnit = iOUnit;
// Set input callback ----> RECORDING
AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = recordingCallback;
callbackStruct.inputProcRefCon = self;
result = AudioUnitSetProperty(iOUnit,
kAudioOutputUnitProperty_SetInputCallback,
kAudioUnitScope_Global,
kInputBus,
&callbackStruct,
sizeof(callbackStruct));
if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty" withStatus: result]; return;}
But I don't know what's wrong and don't know how to digg. Note : The EffectState struct is present because I also try to integrate the BioAudio project ability to write file from buffers.
And Third, I wonder if there something easier to do to record sounds played by my iPhone app (ie microphone excluded) ?
回答1:
Found by myself. I forgot to chain like this :
callbackStruct.inputProcRefCon = &effectState;
This is the code part. Now I have again conceptual issues ...
来源:https://stackoverflow.com/questions/7032468/record-sounds-played-by-my-iphone-app-with-audio-units