bitstream.c

xvid解码的精简版本.非常好的版本,节省了分离xvid源代码的过程

			if (e->interpolate_mc_q) BitstreamSkip(bs, 8);	/* */
			if (e->sadct)		BitstreamSkip(bs, 8);	/* */
			if (e->quarterpel)	BitstreamSkip(bs, 8);	/* */
		}

		if (coding_type == S_VOP && dec->sprite_enable == SPRITE_STATIC) {
			if (e->intra_blocks) BitstreamSkip(bs, 8);	/* */
			if (e->not_coded_blocks) BitstreamSkip(bs, 8);	/* */
			if (e->dct_coefs)	BitstreamSkip(bs, 8);	/* */
			if (e->dct_lines)	BitstreamSkip(bs, 8);	/* */
			if (e->vlc_symbols)	BitstreamSkip(bs, 8);	/* */
			if (e->vlc_bits)	BitstreamSkip(bs, 8);	/* */
			if (e->inter_blocks) BitstreamSkip(bs, 8);	/* */
			if (e->inter4v_blocks)	BitstreamSkip(bs, 8);	/* */
			if (e->apm)			BitstreamSkip(bs, 8);	/* */
			if (e->npm)			BitstreamSkip(bs, 8);	/* */
			if (e->forw_back_mc_q)	BitstreamSkip(bs, 8);	/* */
			if (e->halfpel2)	BitstreamSkip(bs, 8);	/* */
			if (e->halfpel4)	BitstreamSkip(bs, 8);	/* */
			if (e->interpolate_mc_q) BitstreamSkip(bs, 8);	/* */
		}
	}
}


/*
decode headers
returns coding_type, or -1 if error
*/

#define VIDOBJ_START_CODE_MASK		0x0000001f
#define VIDOBJLAY_START_CODE_MASK	0x0000000f

int
BitstreamReadHeaders(Bitstream * bs,
					 DECODER * dec,
					 uint32_t * rounding,
					 uint32_t * quant,
					 uint32_t * fcode_forward,
					 uint32_t * fcode_backward,
					 uint32_t * intra_dc_threshold,
					 WARPPOINTS *gmc_warp)
{
	uint32_t vol_ver_id;
	uint32_t coding_type;
	uint32_t start_code;
	uint32_t time_incr = 0;
	int32_t time_increment = 0;
	int resize = 0;

	while ((BitstreamPos(bs) >> 3) + 4 <= bs->length) {

		BitstreamByteAlign(bs);
		start_code = BitstreamShowBits(bs, 32);

		if (start_code == VISOBJSEQ_START_CODE) {

			int profile;

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

			BitstreamSkip(bs, 32);	/* visual_object_sequence_start_code */
			profile = BitstreamGetBits(bs, 8);	/* profile_and_level_indication */

			DPRINTF(XVID_DEBUG_HEADER, "profile_and_level_indication %i\n", profile);

		} else if (start_code == VISOBJSEQ_STOP_CODE) {

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

			DPRINTF(XVID_DEBUG_STARTCODE, "</visual_object_sequence>\n");

		} else if (start_code == VISOBJ_START_CODE) {
			int visobj_ver_id;

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

			BitstreamSkip(bs, 32);	/* visual_object_start_code */
			if (BitstreamGetBit(bs))	/* is_visual_object_identified */
			{
				visobj_ver_id = BitstreamGetBits(bs, 4);	/* visual_object_ver_id */
				DPRINTF(XVID_DEBUG_HEADER,"visobj_ver_id %i\n", visobj_ver_id);
				BitstreamSkip(bs, 3);	/* visual_object_priority */
			} else {
				visobj_ver_id = 1;
			}

			if (BitstreamShowBits(bs, 4) != VISOBJ_TYPE_VIDEO)	/* visual_object_type */
			{
				DPRINTF(XVID_DEBUG_ERROR, "visual_object_type != video\n");
				return -1;
			}
			BitstreamSkip(bs, 4);

			/* video_signal_type */

			if (BitstreamGetBit(bs))	/* video_signal_type */
			{
				DPRINTF(XVID_DEBUG_HEADER,"+ video_signal_type\n");
				BitstreamSkip(bs, 3);	/* video_format */
				BitstreamSkip(bs, 1);	/* video_range */
				if (BitstreamGetBit(bs))	/* color_description */
				{
					DPRINTF(XVID_DEBUG_HEADER,"+ color_description");
					BitstreamSkip(bs, 8);	/* color_primaries */
					BitstreamSkip(bs, 8);	/* transfer_characteristics */
					BitstreamSkip(bs, 8);	/* matrix_coefficients */
				}
			}
		} else if ((start_code & ~VIDOBJ_START_CODE_MASK) == VIDOBJ_START_CODE) {

			DPRINTF(XVID_DEBUG_STARTCODE, "<video_object>\n");
			DPRINTF(XVID_DEBUG_HEADER, "vo id %i\n", start_code & VIDOBJ_START_CODE_MASK);

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

		} else if ((start_code & ~VIDOBJLAY_START_CODE_MASK) == VIDOBJLAY_START_CODE) {

			DPRINTF(XVID_DEBUG_STARTCODE, "<video_object_layer>\n");
			DPRINTF(XVID_DEBUG_HEADER, "vol id %i\n", start_code & VIDOBJLAY_START_CODE_MASK);

			BitstreamSkip(bs, 32);	/* video_object_layer_start_code */
			BitstreamSkip(bs, 1);	/* random_accessible_vol */

            BitstreamSkip(bs, 8);   /* video_object_type_indication */

			if (BitstreamGetBit(bs))	/* is_object_layer_identifier */
			{
				DPRINTF(XVID_DEBUG_HEADER, "+ is_object_layer_identifier\n");
				vol_ver_id = BitstreamGetBits(bs, 4);	/* video_object_layer_verid */
				DPRINTF(XVID_DEBUG_HEADER,"ver_id %i\n", vol_ver_id);
				BitstreamSkip(bs, 3);	/* video_object_layer_priority */
			} else {
				vol_ver_id = 1;
			}

			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);
				}