CODEWITHSUNDEEP
core-audioaudiounitcircular-buffer
Gerard
Gerard

Reputation: 349

Reading chunks of audio with ringbuffer

I would like to analyze chunks of audio data of one second. For this purpose I implemented an audio unit that fills a ringbuffer (TPCircularBuffer by Michael Tyson). In another file I try to read chunks of one second using a NStimer. Unfortunately, I receive errors with consuming these data.

The buffer is filled in a kAudioOutputUnitProperty_SetInputCallback and works fine

Device * THIS = (__bridge Device *)inRefCon;
// Render audio into buffer
AudioBufferList bufferList;
bufferList.mNumberBuffers = 1;
bufferList.mBuffers[0].mNumberChannels = 2;
bufferList.mBuffers[0].mData = NULL;
bufferList.mBuffers[0].mDataByteSize = inNumberFrames * sizeof(SInt16) * 2;
CheckError(AudioUnitRender(THIS -> rioUnit, ioActionFlags, inTimeStamp, 1, inNumberFrames, &bufferList), "AudioUnitRender");

// Put audio into circular buffer
TPCircularBufferProduceBytes(&circBuffer, bufferList.mBuffers[0].mData, inNumberFrames * 2 * sizeof(SInt16));

To read one second of samples I implemented te following code:

    - (void)initializeTimer {
        timer = [NSTimer scheduledTimerWithTimeInterval:1
                                                 target:self
                                               selector:@selector(timerFired:)
                                               userInfo:nil
                                                repeats:YES];
    }

    - (void) timerFired:(NSTimer *)theTimer {
        NSLog(@"Reading %i second(s) from ring",1);

        int32_t availableBytes;
        SInt16 *tail = TPCircularBufferTail(&circBuffer, &availableBytes);
        int availableSamples = availableBytes / sizeof(SInt16);
        NSLog(@"Available samples %i", availableSamples);

        for (int i = 0; i < availableSamples; i++) {
            printf("%i\n",tail[i]);
        }

        TPCircularBufferConsume(&circBuffer, sizeof(SInt16) * availableBytes);
    }

However, when I run this code the number of samples is printed but then I receive the following error: Assertion failed: (buffer->fillCount >= 0), function TPCircularBufferConsume, file …/TPCircularBuffer.h, line 142.

Unfortunately, I don’t know what is going wrong with consuming the data. The buffer length is set to samplerate * 2 to be long enough.

I would be very happy if someone knows what is going wrong here.

Upvotes: 1

Views: 336

Answers (1)

hotpaw2
hotpaw2

Reputation: 70673

Your circular buffer isn't long enough. You don't check that the available size is positive before emptying, and the time all your print statements take let the buffer get over-filled. Make the buffer at least 2X larger than your timer, check before emptying, empty the buffer before printing, and use far fewer print statements.

Upvotes: 2

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