mpegaudiodecoder.h

Linux下比较早的基于命令行的DVD播放器

//
// Copyright (c) 2003 by Istv醤 V醨adi
//
// This file is part of dxr3Player, a DVD player written specifically 
// for the DXR3 (aka Hollywood+) decoder card.

// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

#ifndef DXR3PLAYER_OUTPUT_MPEGAUDIODECODER_H
#define DXR3PLAYER_OUTPUT_MPEGAUDIODECODER_H
//------------------------------------------------------------------------------

#include "AudioDecoder.h"

#include "util/AudioFormat.h"

#include <cstdlib>

#include <mad.h>

//------------------------------------------------------------------------------

namespace output {

//------------------------------------------------------------------------------

/**
 * MPEG audio decoder using MAD.
 * FIXME: this should be unified with AC3Decoder.
 */
class MPEGAudioDecoder : public AudioDecoder
{
private:
    /**
     * The type of the samples.
     */
    typedef unsigned short sampleType;

    /**
     * The size of a stereo sample
     */
    static const size_t sampleSize = sizeof(sampleType) * 2;

    /**
     * The size of the frame buffer.
     */
    static const size_t frameBufferSize = 4096;

    /**
     * The maximal number of output samples.
     */
    static const size_t maxOutputSamples = 1152;

    /**
     * The table for bitrates.
     *
     * The first index is for the MPEG versions: 0 -> MPEG 2.5, 1 -> MPEG 1
     * and 2.
     * The second index is for the layers: 0 -> III, 1 -> II, 2 -> I
     * The third index is the bitrate index
     */
    static const size_t bitrateTable[2][3][16];

    /**
     * The table for sample rates.
     *
     * The index is the sample rate index as found in the frame
     * header. The value is the sample rate for MPEG 2.5. It should be
     * multiplied by 2 for MPEG 2 and 4 for MPEG 1.
     */
    static const size_t sampleRateTable[3];

    /**
     * Convert the given sample to our sample type.
     */
    static sampleType convertSample(mad_fixed_t sample);

private:
    /**
     * Buffer for frame data.
     */
    unsigned char frameBuffer[frameBufferSize];

    /**
     * The offset of the next byte to be received from the frame.
     */
    size_t frameOffset;

    /**
     * The frame length;
     */
    size_t frameLength;

    /**
     * The MAD stream.
     */
    mad_stream madStream;

    /**
     * The MAD frame.
     */
    mad_frame madFrame;

    /**
     * The MAD synth structure
     */
    mad_synth madSynth;

public:
    /**
     * Construct the MPEG audio decoder.
     *
     * FIXME: remove the default value
     */
    MPEGAudioDecoder(AudioProcessor* audioProcessor);

    /**
     * Reset the decoder.
     */
    virtual void reset();

    /**
     * @see AudioDecoder::decodePacket
     */
    virtual void decodePacket(const unsigned char* data,
                              size_t length, pts_t packetPTS);

private:
    /**
     * Determine if the decoder is empty.
     */
    bool isEmpty() const;

    /**
     * Decode the given data 
     *
     * @param data the start of the data. Will be moved to the end of
     * the processed data.
     *
     * @return true, if a frame has been decoded, false otherwise.
     */
    bool decode(const unsigned char*& data,
                const unsigned char* end);

    /**
     * Get the length of a frame. It should be called when the 4
     * header bytes are available in the frame buffer. It also filles
     * the sample rate in the format structure.
     */
    size_t getFrameLength();

    /**
     * Copy the data from the given address into the frame buffer,
     * until the given target offset is reached.
     */
    void copy(const unsigned char*& data,
              const unsigned char* end,
              size_t targetOffset);

    /**
     * Decode the frame from the buffer.
     *
     * @return if the decoding was successful.
     */
    bool decodeFrame();

    /**
     * Synthesize the frame into the output buffer.
     */
    void synthesizeFrame();
};

//------------------------------------------------------------------------------

} /* namespace output */

//------------------------------------------------------------------------------
#endif // DXR3PLAYER_OUTPUT_MPEGAUDIODECODER_H

// Local variables:
// mode: c++
// End: