ALACDecoder.java

/*
 * Copyright (c) 2008, 2009, 2010, 2011 Denis Tulskiy
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * version 3 along with this work.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.tulskiy.musique.audio.formats.mp4;

import com.beatofthedrum.alacdecoder.AlacContext;
import com.beatofthedrum.alacdecoder.AlacUtils;
import com.beatofthedrum.alacdecoder.DecodeResult;
import com.tulskiy.musique.audio.Decoder;
import com.tulskiy.musique.playlist.Track;

import javax.sound.sampled.AudioFormat;

/**
* Author: Denis Tulskiy
* Date: 4/2/11
*/
public class ALACDecoder implements Decoder {
    private AlacContext alacContext;
    private AudioFormat audioFormat;

    public static final int destBufferSize = 1024 * 24 * 3; // 24kb buffer = 4096 frames = 1 alac sample (we support max 24bps)
    private int[] pDestBuffer;
    private int bps;
    private int totalSamples;

    @Override
    public boolean open(Track track) {
        alacContext = AlacUtils.AlacOpenFileInput(track.getTrackData().getFile().getAbsolutePath());
        if (alacContext.error) {
            logger.warning("Error while opening alac file: " + alacContext.error_message);
            return false;
        }
        int channels = AlacUtils.AlacGetNumChannels(alacContext);
        totalSamples = AlacUtils.AlacGetNumSamples(alacContext);
        bps = AlacUtils.AlacGetBytesPerSample(alacContext);
        int sampleRate = AlacUtils.AlacGetSampleRate(alacContext);
        int bitps = AlacUtils.AlacGetBitsPerSample(alacContext);

        pDestBuffer = new int[destBufferSize];
        audioFormat = new AudioFormat(sampleRate, bitps, channels, true, false);
        return true;
    }

    @Override
    public AudioFormat getAudioFormat() {
        return audioFormat;
    }

    @Override
    public void seekSample(long sample) {
        AlacUtils.AlacSetPosition(alacContext, sample);
    }

    @Override
    public int decode(byte[] buf) {
        int bytesUnpacked = AlacUtils.AlacUnpackSamples(alacContext, pDestBuffer);
        if (bytesUnpacked > 0) {
            formatSamples(bps, pDestBuffer, 0, buf, bytesUnpacked);
            return bytesUnpacked;
        }
        return -1;
    }

    private void formatSamples(int bps, int[] src, int offset, byte[] dst, int samcnt) {
        int temp;
        int destPos = 0;
        int srcPos = offset;

        switch (bps) {
            case 1:
                while (samcnt > 0) {
                    dst[destPos] = (byte) (0x00FF & (src[srcPos] + 128));
                    destPos++;
                    samcnt--;
                }
                break;

            case 2:
                while (samcnt > 0) {
                    temp = src[srcPos++];
                    dst[destPos++] = (byte) temp;
                    dst[destPos++] = (byte) (temp >>> 8);
                    samcnt = samcnt - 2;
                }
                break;

            case 3:
                while (samcnt > 0) {
                    dst[destPos] = (byte) src[srcPos];
                    destPos++;
                    srcPos++;
                    samcnt--;
                }
                break;
        }
    }

    @Override
    public void close() {
        if (alacContext != null)
            AlacUtils.AlacCloseFile(alacContext);
    }
}