ac3strm_in.cpp

来自「Motion JPEG编解码器源代码」· C++ 代码 · 共 479 行

/*
 *  ac3strm_in.c: AC3 Audio strem class members handling scanning and
 *  buffering raw input stream.
 *
 *  Copyright (C) 2001 Andrew Stevens <[e-mail]>
 *  Copyright (C) 2000,2001 Brent Byeler for original header-structure
 *                          parsing code.
 *
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of version 2 of the GNU General Public License
 *  as published by the Free Software Foundation.
 *
 *  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 <config.h>
#include <math.h>
#include <stdlib.h>

#include "audiostrm.hpp"
#include "interact.hpp"
#include "multiplexor.hpp"

//#define DEBUG_AC3_HEADERS
#define AC3_SYNCWORD            0x0b77
#define AC3_PACKET_SAMPLES      1536

const unsigned int AC3Stream::default_buffer_size = 16*1024;

/// table for the available AC3 bitrates
static const unsigned int ac3_bitrate_index[32] =
{ 32,40,48,56,64,80,96,112,128,160,192,
  224,256,320,384,448,512,576,640,
  0,0,0,0,0,0,0,0,0,0,0,0,0
};

static const unsigned int ac3_frame_size[3][32] =
{
    { 64,80,96,112,128,160,192,224,256,320,384,
      448,512,640,768,896,1024, 1152,1280,
      0,0,0,0,0,0,0,0,0,0,0,0,0
    },
    { 69,87,104,121,139,174,208,243,278,348,417,
      487,557,696,835,975,1114, 1253,1393,
          0,0,0,0,0,0,0,0,0,0,0,0,0
    },
    { 96,120,144,168,192,240,288,336,384,480,576,
      672,768,960,1152,1344, 1536,1728,1920,
      0,0,0,0,0,0,0,0,0,0,0,0,0
    }
}; 

/// table for the available AC3 frequencies
static const unsigned int ac3_frequency[4] = 
{ 48000, 44100, 32000, 0};


AC3Stream::AC3Stream(IBitStream &ibs, Multiplexor &into) : 
	AudioStream( ibs, into )
{
num_frames = 0;
}

bool AC3Stream::Probe(IBitStream &bs )
{
    return bs.GetBits(16) == AC3_SYNCWORD;
}


/*************************************************************************
 *
 * Reads initial stream parameters and displays feedback banner to users
 * @param stream_num AC3 substream ID
 *************************************************************************/


void  AC3Stream::DisplayAc3HeaderInfo()
{
        /* Some stuff to generate frame-header information */
        printf( "bsid         = %d\n", bs.GetBits(5) );
        printf( "bsmode       = 0x%1x\n", bs.GetBits(3) ); 
        int acmode = bs.GetBits(3);
        int nfchans = 0;
        switch( acmode )
        {
        case 0x0 :
            nfchans = 2; break;
        case 0x1 :
            nfchans = 1; break;
        case 0x2 :
            nfchans = 2; break;
        case 0x3 :
        case 0x4 :
            nfchans = 3; break;
        case 0x5 :
        case 0x6 :
            nfchans = 4; break;
        case 0x7 :
            nfchans = 5; break;
        }
        printf( "acmode       = 0x%1x (%d channels)\n", acmode, nfchans ); 
        if( (acmode & 0x1) && (acmode != 1 ) )
            printf( "cmixlev  = %d\n", bs.GetBits(2) ); 
        if( (acmode & 0x4) )
            printf( "smixlev  = %d\n", bs.GetBits(2) ); 
        if( acmode == 2 ) 
            printf( "dsurr    = %d\n", bs.GetBits(2) ); 
        printf( "lfeon        = %d\n", bs.GetBits(1) ); 
        printf( "dialnorm     = %02d\n", bs.GetBits(5) ); 
        int compre = bs.GetBits(1);
        printf( "compre       = %d\n", compre ); 
        if( compre )
            printf( "compr    = %02d\n", bs.GetBits(8) ); 
        int langcode = bs.GetBits(1);
        printf( "langcode     = %d\n", langcode ); 
        if( langcode )
            printf( "langcod  = 0x%02x\n", bs.GetBits(8) ); 
        int audprodie =  bs.GetBits(1);
        printf( "audprodie    = %d\n", audprodie );
        if( audprodie )
        {
            printf( "mixlevel = 0x%02x\n", bs.GetBits(5) );
            printf( "roomtyp  = 0x%02x\n", bs.GetBits(2) );
        }
        if( acmode == 0 )
        {
            printf( "Skipping 1+1 mode parameters\n" );
            bs.GetBits(5+1+8+1+8);
            if( bs.GetBits(1) )
                bs.GetBits(7);
        }
        printf( "Copyright  = %d\n", bs.GetBits(1) ); 
        printf( "Original   = %d\n", bs.GetBits(1) ); 
        int timecod1e = bs.GetBits(1);
        if( timecod1e )
        {
            printf( "timecod1 = 0x%03x\n", bs.GetBits(14) );
        }
        int timecod2e = bs.GetBits(1);
        if( timecod2e )
        {
            printf( "timecod2 = 0x%03x\n", bs.GetBits(14) );
        }
        int addbsie = bs.GetBits(1);
        if( addbsie )
        {
            printf( "addbsil  = %02x\n", bs.GetBits(6) );
        }
        

        // FROM This point on we're actually right into the actual audio block
        printf( "Audio block header...\n" );
        printf( "blksw  [ch] = %02x\n", bs.GetBits(nfchans) );
        printf( "dithflg[ch] = %02x\n", bs.GetBits(nfchans) );
        int dynrnge = bs.GetBits(1);
        printf( "Dynrange    = %d\n", bs.GetBits(1) ); 
        if( dynrnge )
        {
            printf( "dynrng    = %02x\n", bs.GetBits(8) );
        }
        if( acmode == 0 && bs.GetBits(1) )
        {
            printf( "dynrng2   = %02x\n", bs.GetBits(8) );
        }
        int cplstre = bs.GetBits(1);
        printf( "cplstre     = %d\n", cplstre ); 
        int cplinu = 0;
        if( cplstre )
        {
            cplinu = bs.GetBits(1);
            printf( "cplinu    = %d\n", cplinu );
            if( cplinu )
            {
                printf( "Skipping cplinu=1 info...\n");
                bs.GetBits(nfchans);
                if( acmode == 2 )
                    bs.GetBits(1);
                int cplbegf = bs.GetBits(4);
                int cplendf = bs.GetBits(4);
                bs.GetBits(3+cplbegf-cplendf);
            }
        }
        if( cplinu )
        {
            printf( "Warning: no parser for coupling co-ordinates mess\n");
            return;
        }

        if( acmode == 2 )
        {
            int rmatstr = bs.GetBits(1);
            printf( "rmatstr = %d\n", rmatstr );
            printf( "Warning: no parser for rematrixing...\n" );
        }
        

}

void AC3Stream::Init ( const int _stream_num)

{
    unsigned int framesize_code;
    stream_num = _stream_num;
	MuxStream::Init( PRIVATE_STR_1, 
					 1,  // Buffer scale
					 default_buffer_size,
					 false,
					 muxinto.buffers_in_audio,
					 muxinto.always_buffers_in_audio
		);
    mjpeg_info ("Scanning for header info: AC3 Audio stream %02x (%s)",
                stream_num,
                bs.StreamName()
                );

	AU_start = bs.bitcount();
    if (bs.GetBits(16)==AC3_SYNCWORD)
    {
		num_syncword++;
        bs.GetBits(16);         // CRC field
        frequency = bs.GetBits(2);  // Sample rate code
        framesize_code = bs.GetBits(6); // Frame size code
        framesize = ac3_frame_size[frequency][framesize_code>>1];
        framesize = 
            (framesize_code&1) && frequency == 1 ?
            (framesize + 1) << 1:
            (framesize <<1);
            
        header_skip = 5;        // Initially skipped past  5 bytes of header 

	num_frames++;
        access_unit.start = AU_start;
	access_unit.length = framesize;
        mjpeg_info( "AC3 frame size = %d", framesize );
        bit_rate = ac3_bitrate_index[framesize_code>>1];
		samples_per_second = ac3_frequency[frequency];

		/* Presentation time-stamping  */
		access_unit.PTS = static_cast<clockticks>(decoding_order) * 
			static_cast<clockticks>(AC3_PACKET_SAMPLES) * 
			static_cast<clockticks>(CLOCKS)	/ samples_per_second;
		access_unit.DTS = access_unit.PTS;
		access_unit.dorder = decoding_order;
		++decoding_order;
		aunits.Append( access_unit );

    } else
    {
		mjpeg_error ( "Invalid AC3 Audio stream header.");
		exit (1);
    }


	OutputHdrInfo();
}

/// @returns the current bitrate
unsigned int AC3Stream::NominalBitRate()
{ 
	return bit_rate*1024;
}

/// Prefills the internal buffer for output multiplexing.
/// @param frames_to_buffer the number of audio frames to read ahead
void AC3Stream::FillAUbuffer(unsigned int frames_to_buffer )
{
	unsigned int framesize_code;

	last_buffered_AU += frames_to_buffer;
	mjpeg_debug( "Scanning %d AC3 audio frames to frame %d", 
				 frames_to_buffer, last_buffered_AU );

    int skip;
	while( !bs.eos() 
           && decoding_order < last_buffered_AU 
           && !muxinto.AfterMaxPTS(access_unit.PTS)
        )
	{
		skip=access_unit.length-header_skip; 
        bs.SeekFwdBits(skip);
		prev_offset = AU_start;
		AU_start = bs.bitcount();
        if( AU_start - prev_offset != access_unit.length*8 )
        {
            mjpeg_warn( "Discarding incomplete final frame AC3 stream %d!",
                       stream_num);
            aunits.DropLast();
            --decoding_order;
            break;
        }

		/* Check we have reached the end of have  another catenated 
		   stream to process before finishing ... */
		if ( (syncword = bs.GetBits(16))!=AC3_SYNCWORD )
		{
			if( !bs.eos()   )
			{
				mjpeg_error_exit1( "Can't find next AC3 frame: @ %lld we have %04x - broken bit-stream?", AU_start/8, syncword );
            }
            break;
		}

        bs.GetBits(16);         // CRC field
        bs.GetBits(2);          // Sample rate code TOOD: check for change!
        framesize_code = bs.GetBits(6);
        framesize = ac3_frame_size[frequency][framesize_code>>1];
        framesize = 
            (framesize_code&1) && frequency == 1 ?
            (framesize + 1) << 1:
            (framesize <<1);
		access_unit.start = AU_start;
		access_unit.length = framesize;
		access_unit.PTS = static_cast<clockticks>(decoding_order) * 
			static_cast<clockticks>(AC3_PACKET_SAMPLES) * 
			static_cast<clockticks>(CLOCKS)	/ samples_per_second;;
		access_unit.DTS = access_unit.PTS;
		access_unit.dorder = decoding_order;
		decoding_order++;
		aunits.Append( access_unit );
		num_frames++;
		
		num_syncword++;

		if (num_syncword >= old_frames+10 )
		{
			mjpeg_debug ("Got %d frame headers.", num_syncword);
			old_frames=num_syncword;
		}
        
    }
	last_buffered_AU = decoding_order;
	eoscan = bs.eos() || muxinto.AfterMaxPTS(access_unit.PTS);
}


/// Closes the AC3 stream and prints some statistics.
void AC3Stream::Close()
{
    stream_length = AU_start >> 3;
	mjpeg_info ("AUDIO_STATISTICS: %02x", stream_id); 
    mjpeg_info ("Audio stream length %lld bytes.", stream_length);
    mjpeg_info   ("Frames         : %8u",  num_frames);
}

/*************************************************************************
	OutputAudioInfo
	gibt gesammelte Informationen zu den Audio Access Units aus.

	Prints information on audio access units
*************************************************************************/

void AC3Stream::OutputHdrInfo ()
{
	mjpeg_info("AC3 AUDIO STREAM:");

    mjpeg_info ("Bit rate       : %8u bytes/sec (%3u kbit/sec)",
				bit_rate*128, bit_rate);

    if (frequency == 3)
		mjpeg_info ("Frequency      : reserved");
    else
		mjpeg_info ("Frequency      :     %d Hz",
				ac3_frequency[frequency]);

}

/**
Reads the bytes neccessary to complete the current packet payload. 
@param to_read number of bytes to read
@param dst byte buffer pointer to read to 
@returns the number of bytes read
 */
unsigned int 
AC3Stream::ReadPacketPayload(uint8_t *dst, unsigned int to_read)
{
    bitcount_t read_start = bs.GetBytePos();
    // Remember to change StreamHeaderLen if you write a different
    // length re-using this code...
    unsigned int bytes_read = bs.GetBytes( dst+4, to_read-4 );
    assert( bytes_read > 0 );   // Should never try to read nothing
    bs.Flush( read_start );
	clockticks   decode_time;

    unsigned int first_header = 
        (new_au_next_sec || au_unsent > bytes_read )
        ? 0 
        : au_unsent;

    // BUG BUG BUG: how do we set the 1st header pointer if we have
    // the *middle* part of a large frame?
    assert( first_header+2 <= to_read );

    unsigned int syncwords = 0;
    unsigned int bytes_muxed = bytes_read;
  
	if (bytes_muxed == 0 || MuxCompleted() )
    {
		goto completion;
    }


	/* Work through what's left of the current AU and the following AU's
	   updating the info until we reach a point where an AU had to be
	   split between packets.
	   NOTE: It *is* possible for this loop to iterate. 

	   The DTS/PTS field for the packet in this case would have been
	   given the that for the first AU to start in the packet.

	*/

	decode_time = RequiredDTS();
	while (au_unsent < bytes_muxed)
	{	  
        // BUG BUG BUG: if we ever had odd payload / packet size we might
        // split an AC3 frame in the middle of the syncword!
        assert( bytes_muxed > 1 );
		bufmodel.Queued(au_unsent, decode_time);
		bytes_muxed -= au_unsent;
        if( new_au_next_sec )
            ++syncwords;
		if( !NextAU() )
        {
            goto completion;
        }
		new_au_next_sec = true;
		decode_time = RequiredDTS();
	};

	// We've now reached a point where the current AU overran or
	// fitted exactly.  We need to distinguish the latter case
	// so we can record whether the next packet starts with an
	// existing AU or not - info we need to decide what PTS/DTS
	// info to write at the start of the next packet.
	
	if (au_unsent > bytes_muxed)
	{
        if( new_au_next_sec )
            ++syncwords;
		bufmodel.Queued( bytes_muxed, decode_time);
		au_unsent -= bytes_muxed;
		new_au_next_sec = false;
	} 
	else //  if (au_unsent == bytes_muxed)
	{
		bufmodel.Queued(bytes_muxed, decode_time);
        if( new_au_next_sec )
            ++syncwords;
        new_au_next_sec = NextAU();
	}	   
completion:
    // Generate the AC3 header...
    // Note the index counts from the low byte of the offset so
    // the smallest value is 1!
    dst[0] = AC3_SUB_STR_0 + stream_num;
    dst[1] = syncwords;
    dst[2] = (first_header+1)>>8;
    dst[3] = (first_header+1)&0xff;
	return bytes_read+4;
}



/* 
 * Local variables:
 *  c-file-style: "stroustrup"
 *  tab-width: 4
 *  indent-tabs-mode: nil
 * End:
 */