shiftAudioPacket = function shiftAudioPacket() {

        // Flatten data in packet queue
        var data = joinAudioPackets(packetQueue);
        if (!data)
            return null;

        // Pull an appropriate amount of data from the front of the queue
        packetQueue = splitAudioPacket(data);
        data = packetQueue.shift();

        return data;

    }
Shifts off and returns a packet of audio data from the beginning of the
playback queue. The length of this audio packet is determined
dynamically according to the click-reduction algorithm implemented by
splitAudioPacket().

@private
@returns {SampleArray}
    A packet of audio data pulled from the beginning of the playback
    queue.