CODE SNIPPET - PROCESSING AN AUDIO FRAME

// get the codec context
AVCodecContext *codecCtx = _audioStream->codec;

// source variables
int64_t sourceChannelLayout = AV_CH_LAYOUT_STEREO;
int sourceSampleRate = 44100;
enum AVSampleFormat sourceSampleFormat = AV_SAMPLE_FMT_FLT;
int sourceNumberOfChannels = av_get_channel_layout_nb_channels(sourceChannelLayout);
int sourceLineSize = 0;
int sourceNumberOfSamples = (int)sampleBuffer.numberOfSamples;
uint8_t *sourceData = NULL;

// destination variables
int64_t destinationChannelLayout = AV_CH_LAYOUT_STEREO;
int destinationSampleRate = 44100;
enum AVSampleFormat destinationSampleFormat = _outputSampleFormat;
int destinationNumberOfChannels = av_get_channel_layout_nb_channels(destinationChannelLayout);
int destinationLineSize = 0;
int destinationNumberOfSamples = (int)av_rescale_rnd(sourceNumberOfSamples, destinationSampleRate, sourceSampleRate, AV_ROUND_UP);
uint8_t *destinationData = NULL;

// resample the audio to convert to a format that FFmpeg can use

// allocate a resampler context
static struct SwrContext *resamplerCtx;
resamplerCtx = swr_alloc_set_opts(NULL,
                                  destinationChannelLayout,
                                  destinationSampleFormat,
                                  destinationSampleRate,
                                  sourceChannelLayout,
                                  sourceSampleFormat,
                                  sourceSampleRate,
                                  0,
                                  NULL);

if (resamplerCtx == NULL)
{
    // handle error
}

// allocate the source samples buffer
int returnVal = av_samples_alloc(&sourceData,
                                 &sourceLineSize,
                                 sourceNumberOfChannels,
                                 sourceNumberOfSamples,
                                 sourceSampleFormat,
                                 1);

if (returnVal < 0)
{
	// handle error
}

// allocate the destination samples buffer
returnVal = av_samples_alloc(&destinationData,
                             &destinationLineSize,
                             destinationNumberOfChannels,
                             destinationNumberOfSamples,
                             destinationSampleFormat,
                             1);

if (returnVal < 0)
{
	// handle error
}

// fill the source samples buffer
returnVal = av_samples_fill_arrays(&sourceData,
                                   &sourceLineSize,
                                   sampleBuffer.bytesForAllSamples,
                                   sourceNumberOfChannels,
                                   sourceNumberOfSamples,
                                   sourceSampleFormat,
                                   1);

if (returnVal < 0)
{
	// handle error
}

// convert to destination format
returnVal = swr_convert(resamplerCtx,
                        &destinationData,
                        destinationNumberOfSamples,
                        (const uint8_t **)&sourceData,
                        sourceNumberOfSamples);

*** The above line crashes with an EXC_ARITHMETIC error, generally the result of divide by 0