bitstream.c

mpeg4代码,比较具体

						bs_get_matrix(bs, matrix);
						set_intra_matrix(matrix);
					} else
						set_intra_matrix(get_default_intra_matrix());

					if (BitstreamGetBit(bs))	/* load_inter_quant_mat */
					{
						uint8_t matrix[64];
						
						DPRINTF(DPRINTF_HEADER, "load_inter_quant_mat");

						bs_get_matrix(bs, matrix);
						set_inter_matrix(matrix);
					} else
						set_inter_matrix(get_default_inter_matrix());

					if (dec->shape == VIDOBJLAY_SHAPE_GRAYSCALE) {
						DPRINTF(DPRINTF_ERROR, "greyscale matrix not supported");
						return -1;
					}

				}


				if (vol_ver_id != 1) {
					DPRINTF(DPRINTF_DEBUG, "QUARTERPEL BITSTREAM");
					dec->quarterpel = BitstreamGetBit(bs);	/* quarter_sample */
				}
				else
					dec->quarterpel = 0;
				

				if (!BitstreamGetBit(bs))	/* complexity_estimation_disable */
				{
					DPRINTF(DPRINTF_ERROR, "complexity_estimation not supported");
					return -1;
				}

				BitstreamSkip(bs, 1);	/* resync_marker_disable */

				if (BitstreamGetBit(bs))	/* data_partitioned */
				{
					DPRINTF(DPRINTF_ERROR, "data_partitioned not supported");
					BitstreamSkip(bs, 1);	/* reversible_vlc */
				}

				if (vol_ver_id != 1) {
					if (BitstreamGetBit(bs))	/* newpred_enable */
					{
						DPRINTF(DPRINTF_HEADER, "+ newpred_enable");
						BitstreamSkip(bs, 2);	/* requested_upstream_message_type */
						BitstreamSkip(bs, 1);	/* newpred_segment_type */
					}
					if (BitstreamGetBit(bs))	/* reduced_resolution_vop_enable */
					{
						DPRINTF(DPRINTF_ERROR, "reduced_resolution_vop not supported");
						return -1;
					}
				}

				if ((dec->scalability = (int8_t)BitstreamGetBit(bs)))	/* scalability */
				{
					DPRINTF(DPRINTF_ERROR, "scalability not supported");
					return -1;
				}
			} else				/* dec->shape == BINARY_ONLY */
			{
				if (vol_ver_id != 1) {
					if (BitstreamGetBit(bs))	/* scalability */
					{
					DPRINTF(DPRINTF_ERROR, "scalability not supported");
						return -1;
					}
				}
				BitstreamSkip(bs, 1);	/* resync_marker_disable */

			}

		} else if (start_code == GRPOFVOP_START_CODE) {

			DPRINTF(DPRINTF_STARTCODE, "<group_of_vop>");

			BitstreamSkip(bs, 32);
			{
				int hours, minutes, seconds;

				hours = BitstreamGetBits(bs, 5);
				minutes = BitstreamGetBits(bs, 6);
				READ_MARKER();
				seconds = BitstreamGetBits(bs, 6);
				
				DPRINTF(DPRINTF_HEADER, "time %ih%im%is", hours);
			}
			BitstreamSkip(bs, 1);	/* closed_gov */
			BitstreamSkip(bs, 1);	/* broken_link */

		} else if (start_code == VOP_START_CODE) {

			DPRINTF(DPRINTF_STARTCODE, "<vop>");

			BitstreamSkip(bs, 32);	/* vop_start_code */

			coding_type = BitstreamGetBits(bs, 2);	/* vop_coding_type */
			DPRINTF(DPRINTF_HEADER, "coding_type %i", coding_type);

/* *************************** for decode B-frame time *********************** */
			while (BitstreamGetBit(bs) != 0)	/* time_base */
				time_incr++;

			READ_MARKER();

			if (dec->time_inc_bits) {
				time_increment = (BitstreamGetBits(bs, dec->time_inc_bits));	/* vop_time_increment */
			}

			DPRINTF(DPRINTF_HEADER, "time_base %i", time_incr);
			DPRINTF(DPRINTF_HEADER, "time_increment %i", time_increment);

			DPRINTF(DPRINTF_TIMECODE, "%c %i:%i", 
				coding_type == I_VOP ? 'I' : coding_type == P_VOP ? 'P' : 'B',
				time_incr, time_increment);

			if (coding_type != B_VOP) {
				dec->last_time_base = dec->time_base;
				dec->time_base += time_incr;
				dec->time = time_increment;

/*					dec->time_base * time_increment_resolution +
					time_increment;
*/				dec->time_pp = (uint32_t) 
					(time_increment_resolution + dec->time - dec->last_non_b_time)%time_increment_resolution;
				dec->last_non_b_time = dec->time;
			} else {
				dec->time = time_increment; 
/*
					(dec->last_time_base +
					 time_incr) * time_increment_resolution + time_increment; 
*/
				dec->time_bp = (uint32_t) 
					(time_increment_resolution + dec->last_non_b_time - dec->time)%time_increment_resolution;
			}

			READ_MARKER();

			if (!BitstreamGetBit(bs))	/* vop_coded */
			{
				DPRINTF(DPRINTF_HEADER, "vop_coded==false");
				return N_VOP;
			}

			/* if (newpred_enable)
			   {
			   }
			 */

			/* fix a little bug by MinChen <[e-mail]> */
			if ((dec->shape != VIDOBJLAY_SHAPE_BINARY_ONLY) &&
				(coding_type == P_VOP)) {
				*rounding = BitstreamGetBit(bs);	/* rounding_type */
				DPRINTF(DPRINTF_HEADER, "rounding %i", *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();

				DPRINTF(DPRINTF_HEADER, "width %i", width);
				DPRINTF(DPRINTF_HEADER, "height %i", height);
				DPRINTF(DPRINTF_HEADER, "horiz_mc_ref %i", horiz_mc_ref);
				DPRINTF(DPRINTF_HEADER, "vert_mc_ref %i", 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) {
					dec->top_field_first = BitstreamGetBit(bs);
					DPRINTF(DPRINTF_HEADER, "interlace top_field_first %i", dec->top_field_first);
					dec->alternate_vertical_scan = BitstreamGetBit(bs);
					DPRINTF(DPRINTF_HEADER, "interlace alternate_vertical_scan %i", dec->alternate_vertical_scan);
					
				}
			}

			if ((*quant = BitstreamGetBits(bs, dec->quant_bits)) < 1)	/* vop_quant */
				*quant = 1;

			DPRINTF(DPRINTF_HEADER, "quant %i", *quant);

			if (coding_type != I_VOP) {
				*fcode_forward = BitstreamGetBits(bs, 3);	/* fcode_forward */
				DPRINTF(DPRINTF_HEADER, "fcode_forward %i", *fcode_forward);
			}

			if (coding_type == B_VOP) {
				*fcode_backward = BitstreamGetBits(bs, 3);	/* fcode_backward */
				DPRINTF(DPRINTF_HEADER, "fcode_backward %i", *fcode_backward);
			}
			if (!dec->scalability) {
				if ((dec->shape != VIDOBJLAY_SHAPE_RECTANGULAR) &&
					(coding_type != I_VOP)) {
					BitstreamSkip(bs, 1);	/* vop_shape_coding_type */
				}
			}
			return coding_type;

		} else if (start_code == USERDATA_START_CODE) {

			DPRINTF(DPRINTF_STARTCODE, "<user_data>");

			BitstreamSkip(bs, 32);	/* user_data_start_code */

		} else					/* start_code == ? */
		{
			if (BitstreamShowBits(bs, 24) == 0x000001) {
				DPRINTF(DPRINTF_STARTCODE, "<unknown: %x>", BitstreamShowBits(bs, 32));
			}
			BitstreamSkip(bs, 8);
		}
	}
	while ((BitstreamPos(bs) >> 3) < bs->length);

	/*DPRINTF("*** WARNING: no vop_start_code found"); */
	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);
	}
}


/*
	write vol header
*/
void
BitstreamWriteVolHeader(Bitstream * const bs,
						const MBParam * pParam,
						const FRAMEINFO * frame)
{
	/* video object_start_code & vo_id */
	BitstreamPad(bs);
	BitstreamPutBits(bs, VO_START_CODE, 27);
	BitstreamPutBits(bs, 0, 5);

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

	BitstreamPutBit(bs, 0);		/* random_accessible_vol */
	BitstreamPutBits(bs, 1, 8);	/* video_object_type_indication "Video ID" == 00000001 */
	BitstreamPutBit(bs, 0);		/* is_object_layer_identified (0=not given) */
	BitstreamPutBits(bs, 1, 4);	/* aspect_ratio_info (1=1:1) */

	BitstreamPutBit(bs, 1);	/* vol_control_parameters */
	BitstreamPutBits(bs, 1, 2);	/* chroma_format 1="4:2:0" */

	BitstreamPutBit(bs, 1);	/* low_delay */

	BitstreamPutBit(bs, 0);	/* vbv_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
	 */
	BitstreamPutBits(bs, pParam->fbase, 16);


	WRITE_MARKER();

	BitstreamPutBit(bs, 1);		/* fixed_vop_rate = 1 */
	BitstreamPutBits(bs, pParam->fincr, log2bin(pParam->fbase));	/* fixed_vop_time_increment */

	WRITE_MARKER();
	BitstreamPutBits(bs, pParam->width, 13);	/* width */
	WRITE_MARKER();
	BitstreamPutBits(bs, pParam->height, 13);	/* height */
	WRITE_MARKER();

	BitstreamPutBit(bs, frame->global_flags & XVID_INTERLACING);	/* interlace */
	BitstreamPutBit(bs, 1);		/* obmc_disable (overlapped block motion compensation) */
	BitstreamPutBit(bs, 0);		/* sprite_enable */
	BitstreamPutBit(bs, 0);		/* not_8_bit */

	/* quant_type   0=h.263  1=mpeg4(quantizer tables) */
	BitstreamPutBit(bs, pParam->m_quant_type);

	if (pParam->m_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());
		}

	}

	BitstreamPutBit(bs, 1);		/* complexity_estimation_disable */
	BitstreamPutBit(bs, 1);		/* resync_marker_disable */
	BitstreamPutBit(bs, 0);		/* data_partitioned */
	BitstreamPutBit(bs, 0);		/* scalability */

	BitstreamPadAlways(bs);		/* next_start_code() */
}


/*
  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,
						const FRAMEINFO * frame,
						int vop_coded)
{
	uint32_t i;

	BitstreamPad(bs);
	BitstreamPutBits(bs, VOP_START_CODE, 32);

	BitstreamPutBits(bs, frame->coding_type, 2);

	/* time_base = 0  write n x PutBit(1), PutBit(0) */
	for (i = 0; i < frame->seconds; i++) {
		BitstreamPutBit(bs, 1);
	}
	BitstreamPutBit(bs, 0);

	WRITE_MARKER();

	/* time_increment: value=nth_of_sec, nbits = log2(resolution) */
	BitstreamPutBits(bs, frame->ticks, log2bin(pParam->fbase));

	WRITE_MARKER();

	if (!vop_coded) {
		BitstreamPutBits(bs, 0, 1);
		return;
	}

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

	if (frame->coding_type == P_VOP)
		BitstreamPutBits(bs, frame->rounding_type, 1);

	BitstreamPutBits(bs, 0, 3);	/* intra_dc_vlc_threshold */

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

	BitstreamPutBits(bs, frame->quant, 5);	/* quantizer */

	if (frame->coding_type != I_VOP)
		BitstreamPutBits(bs, frame->fcode, 3);	/* forward_fixed_code */

	if (frame->coding_type == B_VOP)
		BitstreamPutBits(bs, frame->bcode, 3);	/* backward_fixed_code */

}