@Override
    public MediaExtractor getAudioExtractor() throws IOException {
        if(mAudioUri != null) {
            // In case of a separate audio file Uri, return an audio extractor
            MediaExtractor mediaExtractor = new MediaExtractor();
            mediaExtractor.setDataSource(mContext, mAudioUri, mAudioHeaders);
            return mediaExtractor;
        }
        // We do not need a separate audio extractor when only a single Uri to a single
        // (multiplexed) file is passed into this class.
        return null;
    }
Creates a media source from separate video and audio URIs.
@param context the context to open the URIs in
@param videoUri the URI pointing to the video source
@param audioUri the URI pointing to the audio source
MediaPlayer/src/main/java/net/protyposis/android/mediaplayer/UriSource.java