Hello,
I am trying to convert PCM audio to iLBC audio using
AudioConverterFillComplexBuffer.
For this I have a sourceFormat and an destinationFormat to create my
AudioConverterRef:
AudioStreamBasicDescription sourceFormat = {0};
sourceFormat.mSampleRate = 44100;
sourceFormat.mFormatID = kAudioFormatLinearPCM;
sourceFormat.mFormatFlags =
kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
sourceFormat.mFramesPerPacket = 1;
sourceFormat.mChannelsPerFrame = 1;
sourceFormat.mBitsPerChannel = 16;
sourceFormat.mBytesPerPacket = 2;
sourceFormat.mBytesPerFrame = 2;
AudioStreamBasicDescription destinationFormat = {0};
destinationFormat.mFormatID = kAudioFormatiLBC;
destinationFormat.mFormatFlags = 0;
destinationFormat.mSampleRate = 8000;
destinationFormat.mChannelsPerFrame = 1;
//160 frames per packet = 20ms mode
destinationFormat.mFramesPerPacket = 160;
destinationFormat.mBytesPerPacket = 38;
OSStatus status = AudioConverterNew(&sourceFormat, & destinationFormat,
&audioConverter);
CAShow() logs the following:
PCMConverter2 0x13fe73590
Input: 1 ch, 44100 Hz, 'lpcm' (0x0000000C) 16-bit little-endian signed
integer
Output: 1 ch, 44100 Hz, 'lpcm' (0x00000009) 32-bit little-endian float
SampleRateConverter 0x13fe60710
Input: 1 ch, 44100 Hz, 'lpcm' (0x00000009) 32-bit little-endian float
Output: 1 ch, 8000 Hz, 'lpcm' (0x00000009) 32-bit little-endian float
Algorithm 'norm', quality 96, Resampler2Wrapper @ 0x13fe511b0
PCMConverter2 0x13fe3b4a0
Input: 1 ch, 8000 Hz, 'lpcm' (0x00000009) 32-bit little-endian float
Output: 1 ch, 8000 Hz, 'lpcm' (0x0000000C) 16-bit little-endian signed
integer
CodecConverter 0x13fe33180
Input: 1 ch, 8000 Hz, 'lpcm' (0x0000000C) 16-bit little-endian signed
integer
Output: 1 ch, 8000 Hz, 'ilbc' (0x00000000) 0 bits/channel, 38
bytes/packet, 160 frames/packet, 0 bytes/frame
codec: 'aenc'/'ilbc'/'appl'
Input layout tag: 0x640001
Output layout tag: 0x640001
Here is my first question: why is the bits per channel and bytes per frame for
my resulting output both 0?
The OSStatus for creating the AudioConverterRef says noErr, so everything seems
to be fine.
Now I want to call the AudioConverterFillComplexBuffer. For this I need an
outOutputData which I create like this:
AudioBufferList outOutputData;
outOutputData.mNumberBuffers = 1;
outOutputData.mBuffers[0].mNumberChannels = 1;
outOutputData.mBuffers[0].mDataByteSize = 38;
outOutputData.mBuffers[0].mData = malloc(38);
The mDataByteSize is 38, because I assume that this should be the 20ms 38
bytes/packet from the AudioConverter. Is this correct?
And so is my UInt32 ioOutputDataPacketSize = 38;
My user data is a circular buffer void *userData = &circularbuffer;
This is how my dataProc looks like:
static OSStatus myAudioConverterComplexInputDataProc( AudioConverterRef
inAudioConverter,
UInt32*
ioNumberDataPackets,
AudioBufferList*
ioData,
AudioStreamPacketDescription** outDataPacketDescription,
void*
inUserData){
TPCircularBuffer *sendBuffer = (TPCircularBuffer*) inUserData;
int32_t availableBytes;
SInt16 *audiobuffer = TPCircularBufferTail(sendBuffer, &availableBytes);
availableBytes = 1024; //min(availableBytes, 1024);
ioData->mBuffers[0].mData = malloc(availableBytes);
memcpy(ioData->mBuffers[0].mData, audiobuffer, availableBytes);
ioData->mBuffers[0].mDataByteSize = availableBytes;
TPCircularBufferConsume(sendBuffer, availableBytes);
return noErr;
}
So how many bytes should we provide? 1024? How is this defined or calculated?
So all in all I call AudioConverterFillComplexBuffer using the given
parameters.
OSStatus status = AudioConverterFillComplexBuffer(audioConverter,
myAudioConverterComplexInputDataProc,
userData,
&ioOutputDataPacketSize,
&outOutputData,
NULL);
This results in an Error: Conversion ('insz’), which represents
kAudioConverterErr_InvalidInputSize.
Do you have any idea where something is wrong with this code?
Thanks a lot and have nice day!
Frederik _______________________________________________
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