videostrm_in.cpp

来自「Motion JPEG编解码器源代码」· C++ 代码 · 共 499 行

/*
 *  inptstrm.c:  Members of video stream class related to raw stream
 *               scanning and buffering.
 *
 *  Copyright (C) 2001 Andrew Stevens <[e-mail]>
 *
 *
 *  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 "videostrm.hpp"
#include "interact.hpp"
#include "multiplexor.hpp"



static void marker_bit (IBitStream &bs, unsigned int what)
{
    if (what != bs.Get1Bit())
    {
        mjpeg_error ("Illegal MPEG stream at offset (bits) %lld: supposed marker bit not found.",bs.bitcount());
        exit (1);
    }
}


void VideoStream::ScanFirstSeqHeader()
{
    if (bs.GetBits( 32)==SEQUENCE_HEADER)
    {
		num_sequence++;
		horizontal_size	= bs.GetBits( 12);
		vertical_size	= bs.GetBits( 12);
		aspect_ratio	= bs.GetBits(  4);
		picture_rate 	= bs.GetBits(  4);
		bit_rate		= bs.GetBits( 18);
		marker_bit( bs, 1);
		vbv_buffer_size	= bs.GetBits( 10);
		CSPF		= bs.Get1Bit();

    } else
    {
		mjpeg_error ("Invalid MPEG Video stream header.");
		exit (1);
    }

	if (mpeg_valid_framerate_code(picture_rate))
    {
		frame_rate = Y4M_RATIO_DBL(mpeg_framerate(picture_rate));
	}
    else
    {
		frame_rate = 25.0;
	}

}




void VideoStream::Init ( const int stream_num )
{
	mjpeg_debug( "SETTING video buffer to %d", parms->DecodeBufferSize() );
	MuxStream::Init( VIDEO_STR_0+stream_num,
					 1,  // Buffer scale
					 parms->DecodeBufferSize()*1024,
					 0,  // Zero stuffing
					 muxinto.buffers_in_video,
					 muxinto.always_buffers_in_video);
    mjpeg_info( "Scanning for header info: Video stream %02x (%s) ",
                VIDEO_STR_0+stream_num,
                bs.StreamName()
                );

	SetBufSize( 4*1024*1024 );
	ScanFirstSeqHeader();

	/* Skip to the end of the 1st AU (*2nd* Picture start!)
	*/
	AU_hdr = SEQUENCE_HEADER;
	AU_pict_data = 0;
	AU_start = 0;
    
    fields_presented = 0;
    group_start_pic = 0;
    group_start_field = 0;
    OutputSeqhdrInfo();
}

//
// Set the Maximum STD buffer delay for this video stream.
// By default we set 1 second but if we have specified a video
// buffer that can hold more than 1.0 seconds demuxed data we
// set the delay to the time to fill the buffer.
//

void VideoStream::SetMaxStdBufferDelay( unsigned int dmux_rate )
{
    double max_delay = CLOCKS;
    if( static_cast<double>(BufferSize()) / dmux_rate > 1.0 )
        max_delay *= static_cast<double>(BufferSize()) / dmux_rate;

    //
    // To enforce a maximum STD buffer residency the
    // calculation is a bit tricky as when we decide to mux we may
    // (but not always) have some of the *previous* picture left to
    // mux in which case it is the timestamp of the next picture that counts.
    // For simplicity we simply reduce the limit by 1.5 frame intervals
    // and use the timestamp for the current picture.
    //
    if( frame_rate > 10.0 )
        max_STD_buffer_delay = static_cast<clockticks>(max_delay * (frame_rate-1.5)/frame_rate);
    else
        max_STD_buffer_delay = static_cast<clockticks>(10.0 * max_delay / frame_rate);

}


//
// Refill the AU unit buffer setting  AU PTS DTS from the scanned
// header information...
//

void VideoStream::FillAUbuffer(unsigned int frames_to_buffer)
{
    if( eoscan )
        return;

	last_buffered_AU += frames_to_buffer;
	mjpeg_debug( "Scanning %d video frames to start of frame %d", 
				 frames_to_buffer, last_buffered_AU );

    // We set a limit of 2M to seek before we give up.
    // This is intentionally very high because some heavily
    // padded still frames may have a loooong gap before
    // a following sequence end marker.
    // IMPORTANT: SeekSync *must* come last otherwise a header
    // will be lost!!!!
	while(!bs.eos() 
          && decoding_order < last_buffered_AU  
          && !muxinto.AfterMaxPTS(access_unit.PTS)
		  && bs.SeekSync( SYNCWORD_START, 24, 2*1024*1024)
		)
	{
		syncword = (SYNCWORD_START<<8) + bs.GetBits( 8);
		if( AU_pict_data )
		{
			
			/* Handle the header *ending* an AU...
			   If we have the AU picture data an AU and have now
			   reached a header marking the end of an AU fill in the
			   the AU length and append it to the list of AU's and
			   start a new AU.  I.e. sequence and gop headers count as
			   part of the AU of the corresponding picture
			*/
			stream_length = bs.bitcount()-static_cast<bitcount_t>(32);
			switch (syncword) 
			{
			case SEQUENCE_HEADER :
                mjpeg_debug( "Seq hdr @ %lld", bs.bitcount() / 8-4 );
			case GROUP_START :
                mjpeg_debug( "Group hdr @ %lld", bs.bitcount() / 8-4 );
			case PICTURE_START :
				access_unit.start = AU_start;
				access_unit.length = static_cast<int>(stream_length - AU_start)>>3;
				access_unit.end_seq = 0;
				avg_frames[access_unit.type-1]+=access_unit.length;
				mjpeg_debug( "AU %d %d %d @ %lld: DTS=%ud", 
                             decoding_order,
                             access_unit.type,
                             access_unit.length,
                             bs.bitcount() / 8-4,
							 static_cast<unsigned int>(access_unit.DTS/300) );


				aunits.Append( access_unit );					
                decoding_order++;
				AU_hdr = syncword;
				AU_start = stream_length;
				AU_pict_data = 0;
				break;
			case SEQUENCE_END:
				access_unit.length = ((stream_length - AU_start)>>3)+4;
				access_unit.end_seq = 1;
				aunits.Append( access_unit );
				mjpeg_info( "Scanned to end AU %d", access_unit.dorder );
				avg_frames[access_unit.type-1]+=access_unit.length;

				/* Do we have a sequence split in the video stream? */
				if( !bs.eos() && 
					bs.GetBits( 32) ==SEQUENCE_HEADER )
				{
					stream_length = bs.bitcount()-static_cast<bitcount_t>(32);
					AU_start = stream_length;
					syncword  = AU_hdr = SEQUENCE_HEADER;
					AU_pict_data = 0;
					if( !muxinto.split_at_seq_end )
						mjpeg_warn("Sequence end marker found in video stream but single-segment splitting specified!" );
				}
				else
				{
					if( !bs.eos() && muxinto.split_at_seq_end )
						mjpeg_warn("No seq. header starting new sequence after seq. end!");
				}
                decoding_order++;
				num_seq_end++;
				break;
			}
		}

		/* Handle the headers starting an AU... */
		switch (syncword) 
		{
		case SEQUENCE_HEADER:
			/* TODO: Really we should update the info here so we can handle
			 streams where parameters change on-the-fly... */
			num_sequence++;
			break;
			
		case GROUP_START:
			num_groups++;
			break;
			
		case PICTURE_START:
			/* We have reached AU's picture data... */
			AU_pict_data = 1;
            mjpeg_debug( "Picture start @ %lld", bs.bitcount() / 8-4 );
			
            prev_temp_ref = temporal_reference;
			temporal_reference = bs.GetBits( 10);
			access_unit.type   = bs.GetBits( 3);

			/* Now scan forward a little for an MPEG-2 picture coding extension
			   so we can get pulldown info (if present) */
			if( bs.SeekSync(EXT_START_CODE, 32, 64) &&
                bs.GetBits(4) == CODING_EXT_ID)
			{
				/* Skip: 4 F-codes (4)... */
				(void)bs.GetBits(16); 
                /* Skip: DC Precision(2) */
                (void)bs.GetBits(2);
                pict_struct = bs.GetBits(2);
                /* Skip: topfirst (1) frame pred dct (1),
                   concealment_mv(1), q_scale_type (1), */
				(void)bs.GetBits(4);	
				/* Skip: intra_vlc_format(1), alternate_scan (1) */
				(void)bs.GetBits(2);	
				repeat_first_field = bs.Get1Bit();
				pulldown_32 |= repeat_first_field;

			}
			else
			{
				repeat_first_field = 0;
                pict_struct = PIC_FRAME;
			}
				
			if( access_unit.type == IFRAME )
			{
                double bits_persec = 
                    static_cast<double>( stream_length - prev_offset) 
                    * 2.0 * frame_rate  
                    / static_cast<double>(fields_presented - group_start_field);
                
				if( bits_persec > max_bits_persec )
				{
					max_bits_persec = bits_persec;
				}
				prev_offset = stream_length;
				group_start_pic = decoding_order;
				group_start_field = fields_presented;
			}

			NextDTSPTS( );

			access_unit.dorder = decoding_order;
			access_unit.porder = temporal_reference + group_start_pic;

			access_unit.seq_header = ( AU_hdr == SEQUENCE_HEADER);

			if ((access_unit.type>0) && (access_unit.type<5))
			{
				num_frames[access_unit.type-1]++;
			}

			
			if ( decoding_order >= old_frames+1000 )
			{
				mjpeg_debug("Got %d picture headers.", decoding_order);
				old_frames = decoding_order;
			}
			
			break;		    

  
				
		}
	}

	last_buffered_AU = decoding_order;
	num_pictures = decoding_order;	
	eoscan = bs.eos() || muxinto.AfterMaxPTS(access_unit.PTS);
}

void VideoStream::Close()
{
    unsigned int comp_bit_rate	;
    unsigned int peak_bit_rate  ;

    stream_length = bs.bitcount() / 8;
    for( int i=0; i<4; i++)
	{
		avg_frames[i] /= num_frames[i] == 0 ? 1 : num_frames[i];
	}

	/* Average and Peak bit rate in 50B/sec units... */
    comp_bit_rate = 
        static_cast<unsigned int>( static_cast<unsigned int>( stream_length / fields_presented * 2 ) 
                                   * frame_rate  + 25) / 50;

	peak_bit_rate = static_cast<unsigned int>((max_bits_persec / 8 + 25) / 50);
	mjpeg_info ("VIDEO_STATISTICS: %02x", stream_id); 
    mjpeg_info ("Video Stream length: %11llu bytes", stream_length);
    mjpeg_info ("Sequence headers: %8u",num_sequence);
    mjpeg_info ("Sequence ends   : %8u",num_seq_end);
    mjpeg_info ("No. Pictures    : %8u",num_pictures);
    mjpeg_info ("No. Groups      : %8u",num_groups);
    mjpeg_info ("No. I Frames    : %8u avg. size%6u bytes",
			  num_frames[0], (uint32_t)avg_frames[0]);
    mjpeg_info ("No. P Frames    : %8u avg. size%6u bytes",
			  num_frames[1], (uint32_t)avg_frames[1]);
    mjpeg_info ("No. B Frames    : %8u avg. size%6u bytes",
			  num_frames[2], (uint32_t)avg_frames[2]);
    mjpeg_info("Average bit-rate : %8u bits/sec",comp_bit_rate*400);
    mjpeg_info("Peak bit-rate    : %8u  bits/sec",peak_bit_rate*400);
	
}
	



/*************************************************************************
	OutputSeqHdrInfo
     Display sequence header parameters
*************************************************************************/

void VideoStream::OutputSeqhdrInfo ()
{
	const char *str;
	mjpeg_info("VIDEO STREAM: %02x", stream_id);

    mjpeg_info ("Frame width     : %u",horizontal_size);
    mjpeg_info ("Frame height    : %u",vertical_size);
	if (mpeg_valid_aspect_code(muxinto.mpeg, aspect_ratio))
		str =  mpeg_aspect_code_definition(muxinto.mpeg,aspect_ratio);
	else
		str = "forbidden";
    mjpeg_info ("Aspect ratio    : %s", str );
				

    if (picture_rate == 0)
		mjpeg_info( "Picture rate    : forbidden");
    else if (mpeg_valid_framerate_code(picture_rate))
		mjpeg_info( "Picture rate    : %2.3f frames/sec",
					Y4M_RATIO_DBL(mpeg_framerate(picture_rate)) );
    else
		mjpeg_info( "Picture rate    : %x reserved",picture_rate);

    if (bit_rate == 0x3ffff)
		{
			bit_rate = 0;
			mjpeg_info( "Bit rate        : variable"); 
		}
    else if (bit_rate == 0)
		mjpeg_info( "Bit rate       : forbidden");
    else
		mjpeg_info( "Bit rate        : %u bits/sec",
					bit_rate*400);

    mjpeg_info("Vbv buffer size : %u bytes",vbv_buffer_size*2048);
    mjpeg_info("CSPF            : %u",CSPF);
}

//
// Compute PTS DTS of current AU in the video sequence being
// scanned.  This is is the PTS/DTS calculation for normal video only.
// It is virtual and over-ridden for non-standard streams (Stills
// etc!).
//

int gopfields_32pd( int temporal_ref, bool repeat_first_field )
{
    int frames2field;
    int frames3field;
    //
    // Assume first presented frame of GOP has temporal ref 0
    if( repeat_first_field )
    {
        frames2field = (temporal_ref+1) / 2;
        frames3field = temporal_ref / 2;
    }
    else
    {
        frames2field = (temporal_ref) / 2;
        frames3field = (temporal_ref+1) / 2;
    }

    return frames2field*2 + frames3field*3;

}

/****************************************************
 *
 * Work out DTS PTS stamps for the current AU.
 * Note: Current strategy assumes decoders model 'ideal'
 * timing with instantaneous decoding.
 * This makes sense it is what is assumed for B-frames anyway
 * (no seperate DTS).
 *
 ******************************************************/

void VideoStream::NextDTSPTS()
{
    const int decode_delay = 0;
    int startup_skew = 2;
    int decode_fields, present_fields;
    if( pict_struct != PIC_FRAME )
    {
		decode_fields = fields_presented;
        present_fields = temporal_reference*2 + group_start_field+decode_delay/2;
        if( temporal_reference == prev_temp_ref )
            present_fields += 1;
        fields_presented += 1;
    }	
    else if( pulldown_32 )
	{
        present_fields = group_start_field  + startup_skew + decode_delay +
            gopfields_32pd( temporal_reference, repeat_first_field );
        
        if( decoding_order == 0 )
        {
            // Special case... first IFRAME is not decoded during presentation
            // of previous ref frame but immediately at start
            decode_fields = 0;
            prev_ref_present = present_fields ;
        }
        else if( access_unit.type == IFRAME || access_unit.type == PFRAME )
        {
            decode_fields = prev_ref_present-decode_delay;
            prev_ref_present = present_fields;
        }
        else
        {
            decode_fields = present_fields - decode_delay;
        }
        fields_presented += repeat_first_field ? 3 : 2;
	}
    else
	{
        decode_fields = decoding_order*2;
        present_fields = (temporal_reference + group_start_pic)*2
            + startup_skew + decode_delay;
		fields_presented += 2;
	}

    access_unit.DTS = static_cast<clockticks>
        (decode_fields * (double)(CLOCKS/2) / frame_rate);
    
    access_unit.PTS = static_cast<clockticks>
        (present_fields * (double)(CLOCKS/2) / frame_rate);
}




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