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Pure Java implementation of video/audio codecs and formats
There is a newer version: 0.2.5
package net.sourceforge.jaad.aac;
import org.jcodec.common.logging.Logger;

import net.sourceforge.jaad.aac.filterbank.FilterBank;
import net.sourceforge.jaad.aac.syntax.BitStream;
import net.sourceforge.jaad.aac.syntax.IBitStream;
import net.sourceforge.jaad.aac.syntax.PCE;
import net.sourceforge.jaad.aac.syntax.SyntacticElements;
import net.sourceforge.jaad.aac.syntax.SyntaxConstants;
import net.sourceforge.jaad.aac.transport.ADIFHeader;

/**
 * This class is part of JAAD ( jaadec.sourceforge.net ) that is distributed
 * under the Public Domain license. Code changes provided by the JCodec project
 * are distributed under FreeBSD license.
 * 
 * Main AAC decoder class
 * 
 * @author in-somnia
 */
public class Decoder implements SyntaxConstants {
    private final DecoderConfig config;
    private final SyntacticElements syntacticElements;
    private final FilterBank filterBank;
    private IBitStream _in;
    private ADIFHeader adifHeader;

    /**
     * The methods returns true, if a profile is supported by the decoder.
     * 
     * @param profile
     *            an AAC profile
     * @return true if the specified profile can be decoded
     * @see Profile#isDecodingSupported()
     */
    public static boolean canDecode(Profile profile) {
        return profile.isDecodingSupported();
    }

    /**
     * Initializes the decoder with a MP4 decoder specific info.
     *
     * After this the MP4 frames can be passed to the
     * decodeFrame(byte[], SampleBuffer) method to decode them.
     * 
     * @param decoderSpecificInfo
     *            a byte array containing the decoder specific info from an MP4
     *            container
     * @throws AACException
     *             if the specified profile is not supported
     */
    public Decoder(byte[] decoderSpecificInfo) throws AACException {
        config = DecoderConfig.parseMP4DecoderSpecificInfo(decoderSpecificInfo);
        if (config == null)
            throw new IllegalArgumentException("illegal MP4 decoder specific info");

        if (!canDecode(config.getProfile()))
            throw new AACException("unsupported profile: " + config.getProfile().getDescription());

        syntacticElements = new SyntacticElements(config);
        filterBank = new FilterBank(config.isSmallFrameUsed(), config.getChannelConfiguration().getChannelCount());

        _in = new BitStream();

        Logger.debug("profile: {0}", config.getProfile());
        Logger.debug("sf: {0}", config.getSampleFrequency().getFrequency());
        Logger.debug("channels: {0}", config.getChannelConfiguration().getDescription());
    }

    public DecoderConfig getConfig() {
        return config;
    }

    /**
     * Decodes one frame of AAC data in frame mode and returns the raw PCM data.
     * 
     * @param frame
     *            the AAC frame
     * @param buffer
     *            a buffer to hold the decoded PCM data
     * @throws AACException
     *             if decoding fails
     */
    public void decodeFrame(byte[] frame, SampleBuffer buffer) throws AACException {
        if (frame != null)
            _in.setData(frame);
        Logger.debug("bits left " + _in.getBitsLeft());
        try {
            decode(buffer);
        } catch (AACException e) {
            if (!e.isEndOfStream())
                throw e;
            else
                Logger.warn("unexpected end of frame");
        }
    }

    private void decode(SampleBuffer buffer) throws AACException {
        if (ADIFHeader.isPresent(_in)) {
            adifHeader = ADIFHeader.readHeader(_in);
            final PCE pce = adifHeader.getFirstPCE();
            config.setProfile(pce.getProfile());
            config.setSampleFrequency(pce.getSampleFrequency());
            config.setChannelConfiguration(ChannelConfiguration.forInt(pce.getChannelCount()));
        }

        if (!canDecode(config.getProfile()))
            throw new AACException("unsupported profile: " + config.getProfile().getDescription());

        syntacticElements.startNewFrame();

        try {
            //1: bitstream parsing and noiseless coding
            syntacticElements.decode(_in);
            //2: spectral processing
            syntacticElements.process(filterBank);
            //3: send to output buffer
            syntacticElements.sendToOutput(buffer);
        } catch (AACException e) {
            buffer.setData(new byte[0], 0, 0, 0, 0);
            throw e;
        } catch (Exception e) {
            buffer.setData(new byte[0], 0, 0, 0, 0);
            throw AACException.wrap(e);
        }
    }
}