MpegBitstream.cxx

Go to the documentation of this file.

/*
 * Copyright (c) 2004 MUSIC TECHNOLOGY GROUP (MTG)
 *                         UNIVERSITAT POMPEU FABRA
 *
 *
 * 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
 *
 */

#include "MpegBitstream.hxx"
#include "Assert.hxx"
#include <cstring>
#include <iostream>

namespace CLAM
{

namespace AudioCodecs
{
        // MRJ: This number was extracted from Underbit's own
        // mp3 player code ( mad-0.14.2b2, player.c:86 ). As they
        // say: 40000 bytes is worth 2.5 secs of audio on a stream
        // with 128 kpbs, 1s with 320 kbps
        const int MpegBitstream::mInputBufferSize = 5*8192;
        
        MpegBitstream::MpegBitstream( FILE* bitstream )
                : mpFile( bitstream )
        {
                mInputBuffer = new unsigned char[mInputBufferSize];
        }

        MpegBitstream::MpegBitstream()
        {
                mInputBuffer = new unsigned char[mInputBufferSize];
        }
        
        MpegBitstream::~MpegBitstream()
        {
                if ( mInputBuffer )
                        delete [] mInputBuffer;
        }

        void MpegBitstream::Init( FILE* fp )
        {
                mpFile = fp;
                Init();
        }

        void MpegBitstream::Init()
        {
                mad_stream_init( &mBitstream );
                mad_frame_init( &mCurrentFrame );
                mad_synth_init( &mMpegSynth );
                mad_timer_reset( &mStreamTimer );
                mFatalError = false;
        }

        TTime MpegBitstream::Finish()
        {
                mad_synth_finish( &mMpegSynth );
                mad_frame_finish( &mCurrentFrame );
                mad_stream_finish( &mBitstream );

                return (TTime)mad_timer_count( mStreamTimer, MAD_UNITS_MILLISECONDS );
        }

        bool MpegBitstream::EOS()
        {
                if ( feof( mpFile ) ) // no more frames
                        return true;
                return false;
                                
        }

        bool MpegBitstream::NextFrame()
        {
                bool validFrameFound = false;

                while( !validFrameFound && !FatalError() )
                {
                        // the first condition ( mStream.buffer == NULL ) handles the first time we 
                        // seek a new Mpeg frame since the stream object does not have a buffer attached.                       
                        // Last time we tried to decode a frame, there wasn't enough data on the buffer,
                        // so we must re-read from the file.

                        if ( mBitstream.buffer == NULL 
                             || mBitstream.error == MAD_ERROR_BUFLEN ) 
                        {

                                TSize readSize, remaining;
                                unsigned char*  readStart;
                        
                                if ( mBitstream.next_frame != NULL )
                                {
                                        remaining = mBitstream.bufend - mBitstream.next_frame;
                                        memmove( mInputBuffer, mBitstream.next_frame, remaining );
                                        readStart = mInputBuffer+remaining;
                                        readSize = mInputBufferSize - remaining;
                                }
                                else
                                {
                                        readSize = mInputBufferSize;
                                        readStart = mInputBuffer;
                                        remaining = 0;
                                }
                                
                                TSize readbytes = fread( readStart, sizeof(unsigned char), readSize, mpFile );
                        
                                if ( readbytes == 0 ) // Nothing read
                                        return false;
                                else if ( readbytes < readSize ) // Less bytes than expected were read
                                {
                                        CLAM_DEBUG_ASSERT( readStart + readbytes + MAD_BUFFER_GUARD <=
                                                           mInputBuffer + mInputBufferSize,
                                                           "Whoops! no room left for buffer guard bytes" );
                                        unsigned char* startPadding = readStart + readbytes;

                                        for ( int i = 0; i < MAD_BUFFER_GUARD; i++ )
                                                startPadding[i] = 0;

                                        readSize = readbytes + MAD_BUFFER_GUARD;
                                }
                                else
                                        readSize = readbytes;

                        
                                mad_stream_buffer( &mBitstream, mInputBuffer, readSize+remaining );
                                mBitstream.error = MAD_ERROR_NONE;
                        }
                        
                        
                        if (mad_frame_decode( &mCurrentFrame, &mBitstream )==-1 ) // error
                        {
                                // some *recoverable* error occured
                                if ( !MAD_RECOVERABLE( mBitstream.error ) )
                                        if ( mBitstream.error != MAD_ERROR_BUFLEN )                                     
                                                mFatalError = true;                                                             
                        }
                        else // frame was decoded right
                        {
                                // we signal that a good frame has been decoded
                                validFrameFound = true;
                                // we add this frame duration to the bitstream internal timer
                                mad_timer_add( &mStreamTimer, mCurrentFrame.header.duration );
                        }


                }

                return validFrameFound;

        }

        bool MpegBitstream::FatalError()
        {
                return mFatalError || ferror(mpFile)!=0;
        }

        bool MpegBitstream::SynthesizeCurrent()
        {
                mad_synth_frame( &mMpegSynth, &mCurrentFrame );

                return true;
        }

        struct mad_frame& MpegBitstream::CurrentFrame()
        {
                return mCurrentFrame;
        }

        struct mad_synth& MpegBitstream::CurrentSynthesis()
        {
                return mMpegSynth;
        }
        
}

}

---