Fix WAVExtractor to output full audio frames only

        maxBytesToRead = maxBytesAvailable;

    }

    // read only integral amounts of audio unit frames.

    const size_t inputUnitFrameSize = mNumChannels * mBitsPerSample / 8;

    maxBytesToRead -= maxBytesToRead % inputUnitFrameSize;

    if (mWaveFormat == WAVE_FORMAT_MSGSM) {

        // Microsoft packs 2 frames into 65 bytes, rather than using separate 33-byte frames,

        // so read multiples of 65, and use smaller buffers to account for ~10:1 expansion ratio