bitstream.c

这是一个压缩解压包,用C语言进行编程的,里面有详细的源代码.

			dec->aspect_ratio = BitstreamGetBits(bs, 4);

			if (dec->aspect_ratio == VIDOBJLAY_AR_EXTPAR)	/* aspect_ratio_info */
			{
				DPRINTF(XVID_DEBUG_HEADER, "+ aspect_ratio_info\n");
				dec->par_width = BitstreamGetBits(bs, 8);	/* par_width */
				dec->par_height = BitstreamGetBits(bs, 8);	/* par_height */
			}

			if (BitstreamGetBit(bs))	/* vol_control_parameters */
			{
				DPRINTF(XVID_DEBUG_HEADER, "+ vol_control_parameters\n");
				BitstreamSkip(bs, 2);	/* chroma_format */
				dec->low_delay = BitstreamGetBit(bs);	/* low_delay */
				DPRINTF(XVID_DEBUG_HEADER, "low_delay %i\n", dec->low_delay);
				if (BitstreamGetBit(bs))	/* vbv_parameters */
				{
					unsigned int bitrate;
					unsigned int buffer_size;
					unsigned int occupancy;

					DPRINTF(XVID_DEBUG_HEADER,"+ vbv_parameters\n");

					bitrate = BitstreamGetBits(bs,15) << 15;	/* first_half_bit_rate */
					READ_MARKER();
					bitrate |= BitstreamGetBits(bs,15);		/* latter_half_bit_rate */
					READ_MARKER();

					buffer_size = BitstreamGetBits(bs, 15) << 3;	/* first_half_vbv_buffer_size */
					READ_MARKER();
					buffer_size |= BitstreamGetBits(bs, 3);		/* latter_half_vbv_buffer_size */

					occupancy = BitstreamGetBits(bs, 11) << 15;	/* first_half_vbv_occupancy */
					READ_MARKER();
					occupancy |= BitstreamGetBits(bs, 15);	/* latter_half_vbv_occupancy */
					READ_MARKER();

					DPRINTF(XVID_DEBUG_HEADER,"bitrate %d (unit=400 bps)\n", bitrate);
					DPRINTF(XVID_DEBUG_HEADER,"buffer_size %d (unit=16384 bits)\n", buffer_size);
					DPRINTF(XVID_DEBUG_HEADER,"occupancy %d (unit=64 bits)\n", occupancy);
				}
			}else{
				dec->low_delay = dec->low_delay_default;
			}

			dec->shape = BitstreamGetBits(bs, 2);	/* video_object_layer_shape */

			DPRINTF(XVID_DEBUG_HEADER, "shape %i\n", dec->shape);
			if (dec->shape != VIDOBJLAY_SHAPE_RECTANGULAR)
			{
				DPRINTF(XVID_DEBUG_ERROR,"non-rectangular shapes are not supported\n");
			}

			if (dec->shape == VIDOBJLAY_SHAPE_GRAYSCALE && vol_ver_id != 1) {
				BitstreamSkip(bs, 4);	/* video_object_layer_shape_extension */
			}

			READ_MARKER();

			/********************** for decode B-frame time ***********************/
			dec->time_inc_resolution = BitstreamGetBits(bs, 16);	/* vop_time_increment_resolution */
			DPRINTF(XVID_DEBUG_HEADER,"vop_time_increment_resolution %i\n", dec->time_inc_resolution);

			if (dec->time_inc_resolution > 0) {
				dec->time_inc_bits = MAX(log2bin(dec->time_inc_resolution-1), 1);
			} else {
				/* for "old" xvid compatibility, set time_inc_bits = 1 */
				dec->time_inc_bits = 1;
			}

			READ_MARKER();

			if (BitstreamGetBit(bs))	/* fixed_vop_rate */
			{
				DPRINTF(XVID_DEBUG_HEADER, "+ fixed_vop_rate\n");
				BitstreamSkip(bs, dec->time_inc_bits);	/* fixed_vop_time_increment */
			}

			if (dec->shape != VIDOBJLAY_SHAPE_BINARY_ONLY) {

				if (dec->shape == VIDOBJLAY_SHAPE_RECTANGULAR) {
					uint32_t width, height;

					READ_MARKER();
					width = BitstreamGetBits(bs, 13);	/* video_object_layer_width */
					READ_MARKER();
					height = BitstreamGetBits(bs, 13);	/* video_object_layer_height */
					READ_MARKER();

					DPRINTF(XVID_DEBUG_HEADER, "width %i\n", width);
					DPRINTF(XVID_DEBUG_HEADER, "height %i\n", height);

					if (dec->width != width || dec->height != height)
					{
						if (dec->fixed_dimensions)
						{
							DPRINTF(XVID_DEBUG_ERROR, "decoder width/height does not match bitstream\n");
							return -1;
						}
						resize = 1;
						dec->width = width;
						dec->height = height;
					}
				}

				dec->interlacing = BitstreamGetBit(bs);
				DPRINTF(XVID_DEBUG_HEADER, "interlacing %i\n", dec->interlacing);

				if (!BitstreamGetBit(bs))	/* obmc_disable */
				{
					DPRINTF(XVID_DEBUG_ERROR, "obmc_disabled==false not supported\n");
					/* TODO */
					/* fucking divx4.02 has this enabled */
				}

				dec->sprite_enable = BitstreamGetBits(bs, (vol_ver_id == 1 ? 1 : 2));	/* sprite_enable */

				if (dec->sprite_enable == SPRITE_STATIC || dec->sprite_enable == SPRITE_GMC)
				{
					int low_latency_sprite_enable;

					if (dec->sprite_enable != SPRITE_GMC)
					{
						int sprite_width;
						int sprite_height;
						int sprite_left_coord;
						int sprite_top_coord;
						sprite_width = BitstreamGetBits(bs, 13);		/* sprite_width */
						READ_MARKER();
						sprite_height = BitstreamGetBits(bs, 13);	/* sprite_height */
						READ_MARKER();
						sprite_left_coord = BitstreamGetBits(bs, 13);	/* sprite_left_coordinate */
						READ_MARKER();
						sprite_top_coord = BitstreamGetBits(bs, 13);	/* sprite_top_coordinate */
						READ_MARKER();
					}
					dec->sprite_warping_points = BitstreamGetBits(bs, 6);		/* no_of_sprite_warping_points */
					dec->sprite_warping_accuracy = BitstreamGetBits(bs, 2);		/* sprite_warping_accuracy */
					dec->sprite_brightness_change = BitstreamGetBits(bs, 1);		/* brightness_change */
					if (dec->sprite_enable != SPRITE_GMC)
					{
						low_latency_sprite_enable = BitstreamGetBits(bs, 1);		/* low_latency_sprite_enable */
					}
				}

				if (vol_ver_id != 1 &&
					dec->shape != VIDOBJLAY_SHAPE_RECTANGULAR) {
					BitstreamSkip(bs, 1);	/* sadct_disable */
				}

				if (BitstreamGetBit(bs))	/* not_8_bit */
				{
					DPRINTF(XVID_DEBUG_HEADER, "not_8_bit==true (ignored)\n");
					dec->quant_bits = BitstreamGetBits(bs, 4);	/* quant_precision */
					BitstreamSkip(bs, 4);	/* bits_per_pixel */
				} else {
					dec->quant_bits = 5;
				}

				if (dec->shape == VIDOBJLAY_SHAPE_GRAYSCALE) {
					BitstreamSkip(bs, 1);	/* no_gray_quant_update */
					BitstreamSkip(bs, 1);	/* composition_method */
					BitstreamSkip(bs, 1);	/* linear_composition */
				}

				dec->quant_type = BitstreamGetBit(bs);	/* quant_type */
				DPRINTF(XVID_DEBUG_HEADER, "quant_type %i\n", dec->quant_type);

				if (dec->quant_type) {
					if (BitstreamGetBit(bs))	/* load_intra_quant_mat */
					{
						uint8_t matrix[64];

						DPRINTF(XVID_DEBUG_HEADER, "load_intra_quant_mat\n");

						bs_get_matrix(bs, matrix);
						set_intra_matrix(dec->mpeg_quant_matrices, matrix);
					} else
						set_intra_matrix(dec->mpeg_quant_matrices, get_default_intra_matrix());

					if (BitstreamGetBit(bs))	/* load_inter_quant_mat */
					{
						uint8_t matrix[64];

						DPRINTF(XVID_DEBUG_HEADER, "load_inter_quant_mat\n");

						bs_get_matrix(bs, matrix);
						set_inter_matrix(dec->mpeg_quant_matrices, matrix);
					} else
						set_inter_matrix(dec->mpeg_quant_matrices, get_default_inter_matrix());

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

				}


				if (vol_ver_id != 1) {
					dec->quarterpel = BitstreamGetBit(bs);	/* quarter_sample */
					DPRINTF(XVID_DEBUG_HEADER,"quarterpel %i\n", dec->quarterpel);
				}
				else
					dec->quarterpel = 0;


				dec->complexity_estimation_disable = BitstreamGetBit(bs);	/* complexity estimation disable */
				if (!dec->complexity_estimation_disable)
				{
					read_vol_complexity_estimation_header(bs, dec);
				}

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

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

				if (vol_ver_id != 1) {
					dec->newpred_enable = BitstreamGetBit(bs);
					if (dec->newpred_enable)	/* newpred_enable */
					{
						DPRINTF(XVID_DEBUG_HEADER, "+ newpred_enable\n");
						BitstreamSkip(bs, 2);	/* requested_upstream_message_type */
						BitstreamSkip(bs, 1);	/* newpred_segment_type */
					}
					dec->reduced_resolution_enable = BitstreamGetBit(bs);	/* reduced_resolution_vop_enable */
					DPRINTF(XVID_DEBUG_HEADER, "reduced_resolution_enable %i\n", dec->reduced_resolution_enable);
				}
				else
				{
					dec->newpred_enable = 0;
					dec->reduced_resolution_enable = 0;
				}

				dec->scalability = BitstreamGetBit(bs);	/* scalability */
				if (dec->scalability)
				{
					DPRINTF(XVID_DEBUG_ERROR, "scalability not supported\n");
					BitstreamSkip(bs, 1);	/* hierarchy_type */
					BitstreamSkip(bs, 4);	/* ref_layer_id */
					BitstreamSkip(bs, 1);	/* ref_layer_sampling_direc */
					BitstreamSkip(bs, 5);	/* hor_sampling_factor_n */
					BitstreamSkip(bs, 5);	/* hor_sampling_factor_m */
					BitstreamSkip(bs, 5);	/* vert_sampling_factor_n */
					BitstreamSkip(bs, 5);	/* vert_sampling_factor_m */
					BitstreamSkip(bs, 1);	/* enhancement_type */
					if(dec->shape == VIDOBJLAY_SHAPE_BINARY /* && hierarchy_type==0 */) {
						BitstreamSkip(bs, 1);	/* use_ref_shape */
						BitstreamSkip(bs, 1);	/* use_ref_texture */
						BitstreamSkip(bs, 5);	/* shape_hor_sampling_factor_n */
						BitstreamSkip(bs, 5);	/* shape_hor_sampling_factor_m */
						BitstreamSkip(bs, 5);	/* shape_vert_sampling_factor_n */
						BitstreamSkip(bs, 5);	/* shape_vert_sampling_factor_m */
					}
					return -1;
				}
			} else				/* dec->shape == BINARY_ONLY */
			{
				if (vol_ver_id != 1) {
					dec->scalability = BitstreamGetBit(bs); /* scalability */
					if (dec->scalability)
					{
						DPRINTF(XVID_DEBUG_ERROR, "scalability not supported\n");
						BitstreamSkip(bs, 4);	/* ref_layer_id */
						BitstreamSkip(bs, 5);	/* hor_sampling_factor_n */
						BitstreamSkip(bs, 5);	/* hor_sampling_factor_m */
						BitstreamSkip(bs, 5);	/* vert_sampling_factor_n */
						BitstreamSkip(bs, 5);	/* vert_sampling_factor_m */
						return -1;
					}
				}
				BitstreamSkip(bs, 1);	/* resync_marker_disable */

			}

			return (resize ? -3 : -2 );	/* VOL */

		} else if (start_code == GRPOFVOP_START_CODE) {

			DPRINTF(XVID_DEBUG_STARTCODE, "<group_of_vop>\n");

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

				hours = BitstreamGetBits(bs, 5);
				minutes = BitstreamGetBits(bs, 6);
				READ_MARKER();
				seconds = BitstreamGetBits(bs, 6);

				DPRINTF(XVID_DEBUG_HEADER, "time %ih%im%is\n", hours,minutes,seconds);
			}
			BitstreamSkip(bs, 1);	/* closed_gov */
			BitstreamSkip(bs, 1);	/* broken_link */

		} else if (start_code == VOP_START_CODE) {

			DPRINTF(XVID_DEBUG_STARTCODE, "<vop>\n");

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

			coding_type = BitstreamGetBits(bs, 2);	/* vop_coding_type */
			DPRINTF(XVID_DEBUG_HEADER, "coding_type %i\n", 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(XVID_DEBUG_HEADER, "time_base %i\n", time_incr);
			DPRINTF(XVID_DEBUG_HEADER, "time_increment %i\n", time_increment);

			DPRINTF(XVID_DEBUG_TIMECODE, "%c %i:%i\n",
				coding_type == I_VOP ? 'I' : coding_type == P_VOP ? 'P' : coding_type == B_VOP ? 'B' : 'S',
				time_incr, time_increment);

			if (coding_type != B_VOP) {
				dec->last_time_base = dec->time_base;
				dec->time_base += time_incr;
				dec->time = dec->time_base*dec->time_inc_resolution + time_increment;
				dec->time_pp = (int32_t)(dec->time - dec->last_non_b_time);
				dec->last_non_b_time = dec->time;
			} else {
				dec->time = (dec->last_time_base + time_incr)*dec->time_inc_resolution + time_increment;
				dec->time_bp = dec->time_pp - (int32_t)(dec->last_non_b_time - dec->time);
			}
			DPRINTF(XVID_DEBUG_HEADER,"time_pp=%i\n", dec->time_pp);
			DPRINTF(XVID_DEBUG_HEADER,"time_bp=%i\n", dec->time_bp);

			READ_MARKER();

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

			if (dec->newpred_enable)
			{
				int vop_id;
				int vop_id_for_prediction;

				vop_id = BitstreamGetBits(bs, MIN(dec->time_inc_bits + 3, 15));
				DPRINTF(XVID_DEBUG_HEADER, "vop_id %i\n", vop_id);
				if (BitstreamGetBit(bs))	/* vop_id_for_prediction_indication */
				{
					vop_id_for_prediction = BitstreamGetBits(bs, MIN(dec->time_inc_bits + 3, 15));
					DPRINTF(XVID_DEBUG_HEADER, "vop_id_for_prediction %i\n", vop_id_for_prediction);
				}
				READ_MARKER();
			}



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

			if (dec->reduced_resolution_enable &&
				dec->shape == VIDOBJLAY_SHAPE_RECTANGULAR &&
				(coding_type == P_VOP || coding_type == I_VOP)) {

				if (BitstreamGetBit(bs));
					DPRINTF(XVID_DEBUG_ERROR, "RRV not supported (anymore)\n");
			}

			if (dec->shape != VIDOBJLAY_SHAPE_RECTANGULAR) {
				if(!(dec->sprite_enable == SPRITE_STATIC && coding_type == I_VOP)) {

					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(XVID_DEBUG_HEADER, "width %i\n", width);
					DPRINTF(XVID_DEBUG_HEADER, "height %i\n", height);
					DPRINTF(XVID_DEBUG_HEADER, "horiz_mc_ref %i\n", horiz_mc_ref);
					DPRINTF(XVID_DEBUG_HEADER, "vert_mc_ref %i\n", 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) {

				if (!dec->complexity_estimation_disable)
				{
					read_vop_complexity_estimation_header(bs, dec, coding_type);
				}

				/* intra_dc_vlc_threshold */
				*intra_dc_threshold =
					intra_dc_threshold_table[BitstreamGetBits(bs, 3)];

				dec->top_field_first = 0;
				dec->alternate_vertical_scan = 0;

				if (dec->interlacing) {
					dec->top_field_first = BitstreamGetBit(bs);
					DPRINTF(XVID_DEBUG_HEADER, "interlace top_field_first %i\n", dec->top_field_first);
					dec->alternate_vertical_scan = BitstreamGetBit(bs);
					DPRINTF(XVID_DEBUG_HEADER, "interlace alternate_vertical_scan %i\n", dec->alternate_vertical_scan);

				}
			}

			if ((dec->sprite_enable == SPRITE_STATIC || dec->sprite_enable== SPRITE_GMC) && coding_type == S_VOP) {

				int i;

				for (i = 0 ; i < dec->sprite_warping_points; i++)
				{
					int length;
					int x = 0, y = 0;

					/* sprite code borowed from ffmpeg; thx Michael Niedermayer <[e-mail]> */
					length = bs_get_spritetrajectory(bs);
					if(length){
						x= BitstreamGetBits(bs, length);
						if ((x >> (length - 1)) == 0) /* if MSB not set it is negative*/
							x = - (x ^ ((1 << length) - 1));
					}
					READ_MARKER();

					length = bs_get_spritetrajectory(bs);
					if(length){
						y = BitstreamGetBits(bs, length);
						if ((y >> (length - 1)) == 0) /* if MSB not set it is negative*/
							y = - (y ^ ((1 << length) - 1));
					}
					READ_MARKER();

					gmc_warp->duv[i].x = x;
					gmc_warp->duv[i].y = y;

					DPRINTF(XVID_DEBUG_HEADER,"sprite_warping_point[%i] xy=(%i,%i)\n", i, x, y);
				}

				if (dec->sprite_brightness_change)
				{
					/* XXX: brightness_change_factor() */
				}
				if (dec->sprite_enable == SPRITE_STATIC)
				{
					/* XXX: todo */
				}

			}

			if ((*quant = BitstreamGetBits(bs, dec->quant_bits)) < 1)	/* vop_quant */
				*quant = 1;
			DPRINTF(XVID_DEBUG_HEADER, "quant %i\n", *quant);

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

			if (coding_type == B_VOP) {
				*fcode_backward = BitstreamGetBits(bs, 3);	/* fcode_backward */
				DPRINTF(XVID_DEBUG_HEADER, "fcode_backward %i\n", *fcode_backward);