Accessing raw audio data with Audio Queue using AudioFileReadPackets
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18-06-2021 - |
سؤال
I'm attempting to access the raw audio data sent to the Audio Queue callback, but I after calling AudioFileReadPackets, the number of bytes (numBytes) is 0.
void AQRecorder::MyInputBufferHandler(void *inUserData, AudioQueueRef inAQ, AudioQueueBufferRef inBuffer, const AudioTimeStamp * inStartTime, UInt32 inNumPackets, const AudioStreamPacketDescription* inPacketDesc) {
AQRecorder *aqr = (AQRecorder *)inUserData;
try {
if (inNumPackets > 0) {
//read packets
UInt32 numBytes;
OSStatus result = AudioFileReadPackets(aqr->mRecordFile, // The audio file from which packets of audio data are to be read.
FALSE, // Set to true to cache the data. Otherwise, set to false.
&numBytes, // On output, a pointer to the number of bytes actually returned.
(__bridge AudioStreamPacketDescription*)inPacketDesc, // A pointer to an array of packet descriptions that have been allocated.
aqr->mRecordPacket, // The packet index of the first packet you want to be returned.
&inNumPackets, // On input, a pointer to the number of packets to read. On output, the number of packets actually read.
inBuffer->mAudioData); // A pointer to user-allocated memory.
inBuffer->mAudioDataByteSize = numBytes;
SInt16 *testBuffer = (SInt16*)inBuffer->mAudioData;
for (int i=0; i < numBytes; i++)
{
UInt16 currentData = testBuffer[i];
printf("Current data in testbuffer is %d", currentData);
}
// if we're not stopping, re-enqueue the buffe so that it gets filled again
if (aqr->IsRunning())
XThrowIfError(AudioQueueEnqueueBuffer(inAQ, inBuffer, 0, NULL), "AudioQueueEnqueueBuffer failed");
} catch (CAXException e) {
char buf[256];
fprintf(stderr, "Error: %s (%s)\n", e.mOperation, e.FormatError(buf));
}
}
I am able to get values between 0 and 4294967296 when I print out just the first index of testBuffer, so it does not seem to be empty. Any ideas why numBytes is 0 after AudioFileReadPackets executes?
المحلول
I'm still unsure as to why numBytes is 0, but I found a workable solution from this question.
To get the size of testBuffer I used the following code:
int sampleCount = inBuffer->mAudioDataBytesCapacity / sizeof(SInt16);
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