bitstream.c

MPEG-4编解码的实现(包括MPEG4视音频编解码)

				}

				if (!BitstreamGetBit(bs))			// resync_marker_disable
				{
					DEBUG("IGNORED/TODO: !resync_marker_disable");
					// TODO
				}

				if (BitstreamGetBit(bs))		// data_partitioned
				{
					DEBUG("+ data_partitioned");
					BitstreamSkip(bs, 1);		// reversible_vlc
				}

				if (vol_ver_id != 1)
				{
					if (BitstreamGetBit(bs))			// newpred_enable
					{
						DEBUG("+ newpred_enable");
						BitstreamSkip(bs, 2);			// requested_upstream_message_type
						BitstreamSkip(bs, 1);			// newpred_segment_type
					}
					if (BitstreamGetBit(bs))			// reduced_resolution_vop_enable
					{
						DEBUG("TODO: reduced_resolution_vop_enable");
						// TODO
						return -1;
					}
				}
				
				if (BitstreamGetBit(bs))	// scalability
				{
					// TODO
					DEBUG("TODO: scalability");
					return -1;
				}
			}
			else	// dec->shape == BINARY_ONLY
			{
				if (vol_ver_id != 1)
				{
					if (BitstreamGetBit(bs))	// scalability
					{
						// TODO
						DEBUG("TODO: scalability");
						return -1;
					}
				}
				BitstreamSkip(bs, 1);			// resync_marker_disable

			}
			if (findvol != 0) return 1;
		}
		else if (start_code == GRPOFVOP_START_CODE)
		{
			// DEBUG("group_of_vop");
			BitstreamSkip(bs, 32);
			{
				int hours, minutes, seconds;
				hours = BitstreamGetBits(bs, 5);
				minutes = BitstreamGetBits(bs, 6);
				READ_MARKER();
				seconds = BitstreamGetBits(bs, 6);
				// DEBUG3("hms", hours, minutes, seconds);
			}
			BitstreamSkip(bs, 1);			// closed_gov
			BitstreamSkip(bs, 1);			// broken_link
		}
		else if (start_code == VOP_START_CODE)
		{
		  if (findvol != 0) return -1;
			// DEBUG("vop_start_code");
			BitstreamSkip(bs, 32);						// vop_start_code

			coding_type = BitstreamGetBits(bs, 2);		// vop_coding_type
			//DEBUG1("coding_type", coding_type);

			while (BitstreamGetBit(bs) != 0) ;			// time_base
	
			READ_MARKER();
	 
			//DEBUG1("time_inc_bits", dec->time_inc_bits);
			//DEBUG1("vop_time_incr", BitstreamShowBits(bs, dec->time_inc_bits));
			if (dec->time_inc_bits)
			{
				BitstreamSkip(bs, dec->time_inc_bits);	// vop_time_increment
			}

			READ_MARKER();

			if (!BitstreamGetBit(bs))					// vop_coded
			{
				return N_VOP;
			}

			/* if (newpred_enable)
			{
			}
			*/

			if (coding_type != I_VOP)
			{
				*rounding = BitstreamGetBit(bs);	// rounding_type
				//DEBUG1("rounding", *rounding);
			}

			/* if (reduced_resolution_enable)
			{
			}
			*/

			if (dec->shape != VIDOBJLAY_SHAPE_RECTANGULAR)
			{
				uint32_t width, height;
				uint32_t horiz_mc_ref, vert_mc_ref;
				
				width = BitstreamGetBits(bs, 13);
				READ_MARKER();
				height = BitstreamGetBits(bs, 13);
				READ_MARKER();
				horiz_mc_ref = BitstreamGetBits(bs, 13);
				READ_MARKER();
				vert_mc_ref = BitstreamGetBits(bs, 13);
				READ_MARKER();

				// DEBUG2("vop_width/height", width, height);
				// DEBUG2("ref             ", horiz_mc_ref, vert_mc_ref);

				BitstreamSkip(bs, 1);				// change_conv_ratio_disable
				if (BitstreamGetBit(bs))			// vop_constant_alpha
				{
					BitstreamSkip(bs, 8);			// vop_constant_alpha_value
				}
			}
				

			if (dec->shape != VIDOBJLAY_SHAPE_BINARY_ONLY)
			{
				// intra_dc_vlc_threshold
				*intra_dc_threshold = intra_dc_threshold_table[ BitstreamGetBits(bs,3) ];

				if (dec->interlacing)
				{
					if ((dec->top_field_first = BitstreamGetBit(bs)))
					{
						DEBUG("vop: top_field_first");
					}
					if ((dec->alternate_vertical_scan = BitstreamGetBit(bs)))
					{
						DEBUG("vop: alternate_vertical_scan");
					}
				}
			}
						
			*quant = BitstreamGetBits(bs, dec->quant_bits);		// vop_quant
			//DEBUG1("quant", *quant);
						
			if (coding_type != I_VOP)
			{
				*fcode = BitstreamGetBits(bs, 3);			// fcode_forward
			}
				
			if (coding_type == B_VOP)
			{
				// *fcode_backward = BitstreamGetBits(bs, 3);		// fcode_backward
			}
			return coding_type;
		}
		else if (start_code == USERDATA_START_CODE)
		{
			// DEBUG("user_data");
			BitstreamSkip(bs, 32);		// user_data_start_code
		}
		else  // start_code == ?
		{
			if (BitstreamShowBits(bs, 24) == 0x000001)
			{
				DEBUG1("*** WARNING: unknown start_code", BitstreamShowBits(bs, 32));
			}
			BitstreamSkip(bs, 8);
		}
	}
	while ((BitstreamPos(bs) >> 3) < bs->length);

	DEBUG("*** WARNING: no vop_start_code found");
	if (findvol != 0) return 0;
	return -1; /* ignore it */
}


/* write custom quant matrix */

static void bs_put_matrix(Bitstream * bs, const int16_t *matrix)
{
	int i, j;
	const int last = matrix[scan_tables[0][63]];

	for (j = 63; j >= 0 && matrix[scan_tables[0][j - 1]] == last; j--) ;

	for (i = 0; i <= j; i++)
	{
		BitstreamPutBits(bs, matrix[scan_tables[0][i]], 8);
	}

	if (j < 63)
	{
		BitstreamPutBits(bs, 0, 8);
	}
}

#ifdef MPEG4IP
/*
	write vosh header
*/
void BitstreamWriteVoshHeader(Bitstream * const bs)
{
    BitstreamPad(bs);

	BitstreamPutBits(bs, VISOBJSEQ_START_CODE, 32);
	BitstreamPutBits(bs, 3, 8);			// Simple Profile @ L3

	// video object_start_code
	BitstreamPutBits(bs, VISOBJ_START_CODE, 32);
	// no verid, priority, or signal type
    BitstreamPutBits(bs, 0x08, 8);
	
	// video object_start_code & vo_id
	BitstreamPutBits(bs, VO_START_CODE, 27);
    BitstreamPutBits(bs, 0, 5);
}
#endif

/*
	write vol header
*/
void BitstreamWriteVolHeader(Bitstream * const bs,
						const MBParam * pParam)
{
    BitstreamPad(bs);

#ifndef MPEG4IP
	// video object_start_code & vo_id
	BitstreamPutBits(bs, VO_START_CODE, 27);
    BitstreamPutBits(bs, 0, 5);
#endif

	// video_object_layer_start_code & vol_id
	BitstreamPutBits(bs, VOL_START_CODE, 28);
	BitstreamPutBits(bs, 0, 4);

	BitstreamPutBit(bs, 0);				// random_accessible_vol
#ifdef MPEG4IP
	BitstreamPutBits(bs, 1, 8);			// video_object_type_indication
										// 1 == simple profile
	BitstreamPutBit(bs, 1);				// is_object_layer_identified 
	BitstreamPutBits(bs, 2, 4);			// visual object layer ver id = 2 
	BitstreamPutBits(bs, 1, 3);			// visual object layer priority = 1 
#else
	BitstreamPutBits(bs, 0, 8);			// video_object_type_indication
	BitstreamPutBit(bs, 0);				// is_object_layer_identified (0=not given)
#endif
	BitstreamPutBits(bs, 1, 4);			// aspect_ratio_info (1=1:1)
	BitstreamPutBit(bs, 0);				// vol_control_parameters (0=not given)
	BitstreamPutBits(bs, 0, 2);			// video_object_layer_shape (0=rectangular)

	WRITE_MARKER();
    
	/* time_increment_resolution; ignored by current decore versions
		eg. 2fps		res=2		inc=1
			25fps		res=25		inc=1
			29.97fps	res=30000	inc=1001
	*/
#ifdef MPEG4IP
	BitstreamPutBits(bs, pParam->fbase, 16);
#else
	BitstreamPutBits(bs, 2, 16);
#endif

	WRITE_MARKER();

	// fixed_vop_rate
	// MPEG4IP - above comment is incorrect, 0 signals variable rate
	BitstreamPutBit(bs, 0);

	// fixed_time_increment: value=nth_of_sec, nbits = log2(resolution)
	// BitstreamPutBits(bs, 0, 15);

	WRITE_MARKER();
	BitstreamPutBits(bs, pParam->width, 13);		// width
	WRITE_MARKER();
	BitstreamPutBits(bs, pParam->height, 13);		// height
	WRITE_MARKER();
	
	BitstreamPutBit(bs, pParam->global_flags & XVID_INTERLACING);		// interlace
	BitstreamPutBit(bs, 1);		// obmc_disable (overlapped block motion compensation)
#ifdef MPEG4IP
	BitstreamPutBits(bs, 0, 2);		// sprite_usage
#else
	BitstreamPutBit(bs, 0);		// sprite_enable
#endif
	BitstreamPutBit(bs, 0);		// not_in_bit

	// quant_type   0=h.263  1=mpeg4(quantizer tables)
	BitstreamPutBit(bs, pParam->quant_type);
	
	if (pParam->quant_type)
	{
		BitstreamPutBit(bs, get_intra_matrix_status());	// load_intra_quant_mat
		if (get_intra_matrix_status())
		{
			bs_put_matrix(bs, get_intra_matrix());
		}

		BitstreamPutBit(bs, get_inter_matrix_status());		// load_inter_quant_mat
		if (get_inter_matrix_status())
		{
			bs_put_matrix(bs, get_inter_matrix());
		}

	}

#ifdef MPEG4IP
	BitstreamPutBit(bs, 0);		// quarter pixel
#endif
	BitstreamPutBit(bs, 1);		// complexity_estimation_disable
	BitstreamPutBit(bs, 1);		// resync_marker_disable
	BitstreamPutBit(bs, 0);		// data_partitioned
#ifdef MPEG4IP
	BitstreamPutBit(bs, 0);		// newpred
	BitstreamPutBit(bs, 0);		// reduced resolution vop
#endif
	BitstreamPutBit(bs, 0);		// scalability
}


/*
  write vop header

  NOTE: doesnt handle bother with time_base & time_inc
  time_base = n seconds since last resync (eg. last iframe)
  time_inc = nth of a second since last resync
  (decoder uses these values to determine precise time since last resync)
*/
void BitstreamWriteVopHeader(Bitstream * const bs,
						const MBParam * pParam)
{
    BitstreamPad(bs);
    BitstreamPutBits(bs, VOP_START_CODE, 32);

    BitstreamPutBits(bs, pParam->coding_type, 2);
    
	// time_base = 0  write n x PutBit(1), PutBit(0)
	BitstreamPutBits(bs, 0, 1);

	WRITE_MARKER();

	// time_increment: value=nth_of_sec, nbits = log2(resolution)
#ifdef MPEG4IP
	BitstreamPutBits(bs, pParam->fincr, pParam->time_inc_bits);		
#else
	BitstreamPutBits(bs, 1, 1);
#endif

	WRITE_MARKER();

	BitstreamPutBits(bs, 1, 1);				// vop_coded

	if (pParam->coding_type != I_VOP)
		BitstreamPutBits(bs, pParam->rounding_type, 1);
    
	BitstreamPutBits(bs, 0, 3);				// intra_dc_vlc_threshold

	if (pParam->global_flags & XVID_INTERLACING)
	{
		BitstreamPutBit(bs, 1);		// top field first
		BitstreamPutBit(bs, 0);		// alternate vertical scan
	}

 	BitstreamPutBits(bs, pParam->quant, 5);			// quantizer
	
	if (pParam->coding_type != I_VOP)
		BitstreamPutBits(bs, pParam->fixed_code, 3);		// fixed_code = [1,4]
}