AudioToolbox.m

    // Step 1: load audio data
    // If the packetIndex is out of range, the ioNumPackets will be 0
    UInt32 ioNumBytes = outBufferSize;
    UInt32 ioNumPackets = numPacketsToRead;
    status = AudioFileReadPacketData(
                            _audioFile,
                            NO,
                            &ioNumBytes,
                            packetDescs,
                            packetIndex,
                            &ioNumPackets,
                            audioQueueBuffer->mAudioData
                            );
    if (status != noErr) NSLog(@"AudioQueueSetParameter failed %d", status);

    // Step 2: prevent load audio data failed
    if (ioNumPackets <= 0) {
        return;
    }

    // Step 3: re-assign the data size
    audioQueueBuffer->mAudioDataByteSize = ioNumBytes;