mbcoding.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

/*****************************************************************************
 *
 *  XVID MPEG-4 VIDEO CODEC
 *  - MB coding -
 *
 *  Copyright (C) 2002 Michael Militzer <[e-mail]>
 *
 *  This program is free software ; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation ; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  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
 *
 * $Id: mbcoding.c,v 1.52 2005/09/13 12:12:15 suxen_drol Exp $
 *
 ****************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "portab.h"
#include "global.h"
#include "bitstream.h"
#include "zigzag.h"
#include "vlc_codes.h"
#include "mbcoding.h"



#define LEVELOFFSET 32

/* Initialized once during xvid_global call
 * RO access is thread safe */
static REVERSE_EVENT DCT3D[2][4096];
static VLC coeff_VLC[2][2][64][64];

int bs_get_spritetrajectory(Bitstream * bs)
{
	int i;
	for (i = 0; i < 12; i++)
	{
		if (BitstreamShowBits(bs, sprite_trajectory_len[i].len) == sprite_trajectory_len[i].code)
		{
			BitstreamSkip(bs, sprite_trajectory_len[i].len);
			return i;
		}
	}
	return -1;
}

void
init_vlc_tables(void)
{
	uint32_t i, j, k, intra, last, run,  run_esc, level, level_esc, escape, escape_len, offset;
	int32_t l;

	for (intra = 0; intra < 2; intra++)
		for (i = 0; i < 4096; i++)
			DCT3D[intra][i].event.level = 0;

	for (intra = 0; intra < 2; intra++) {
		for (last = 0; last < 2; last++) {
			for (run = 0; run < 63 + last; run++) {
				for (level = 0; level < (uint32_t)(32 << intra); level++) {
					offset = !intra * LEVELOFFSET;
					coeff_VLC[intra][last][level + offset][run].len = 128;
				}
			}
		}
	}

	for (intra = 0; intra < 2; intra++) {
		for (i = 0; i < 102; i++) {
			offset = !intra * LEVELOFFSET;

			for (j = 0; j < (uint32_t)(1 << (12 - coeff_tab[intra][i].vlc.len)); j++) {
				DCT3D[intra][(coeff_tab[intra][i].vlc.code << (12 - coeff_tab[intra][i].vlc.len)) | j].len	 = coeff_tab[intra][i].vlc.len;
				DCT3D[intra][(coeff_tab[intra][i].vlc.code << (12 - coeff_tab[intra][i].vlc.len)) | j].event = coeff_tab[intra][i].event;
			}

			coeff_VLC[intra][coeff_tab[intra][i].event.last][coeff_tab[intra][i].event.level + offset][coeff_tab[intra][i].event.run].code
				= coeff_tab[intra][i].vlc.code << 1;
			coeff_VLC[intra][coeff_tab[intra][i].event.last][coeff_tab[intra][i].event.level + offset][coeff_tab[intra][i].event.run].len
				= coeff_tab[intra][i].vlc.len + 1;

			if (!intra) {
				coeff_VLC[intra][coeff_tab[intra][i].event.last][offset - coeff_tab[intra][i].event.level][coeff_tab[intra][i].event.run].code
					= (coeff_tab[intra][i].vlc.code << 1) | 1;
				coeff_VLC[intra][coeff_tab[intra][i].event.last][offset - coeff_tab[intra][i].event.level][coeff_tab[intra][i].event.run].len
					= coeff_tab[intra][i].vlc.len + 1;
			}
		}
	}

	for (intra = 0; intra < 2; intra++) {
		for (last = 0; last < 2; last++) {
			for (run = 0; run < 63 + last; run++) {
				for (level = 1; level < (uint32_t)(32 << intra); level++) {

					if (level <= max_level[intra][last][run] && run <= max_run[intra][last][level])
					    continue;

					offset = !intra * LEVELOFFSET;
                    level_esc = level - max_level[intra][last][run];
					run_esc = run - 1 - max_run[intra][last][level];

					if (level_esc <= max_level[intra][last][run] && run <= max_run[intra][last][level_esc]) {
						escape     = ESCAPE1;
						escape_len = 7 + 1;
						run_esc    = run;
					} else {
						if (run_esc <= max_run[intra][last][level] && level <= max_level[intra][last][run_esc]) {
							escape     = ESCAPE2;
							escape_len = 7 + 2;
							level_esc  = level;
						} else {
							if (!intra) {
								coeff_VLC[intra][last][level + offset][run].code
									= (ESCAPE3 << 21) | (last << 20) | (run << 14) | (1 << 13) | ((level & 0xfff) << 1) | 1;
								coeff_VLC[intra][last][level + offset][run].len = 30;
									coeff_VLC[intra][last][offset - level][run].code
									= (ESCAPE3 << 21) | (last << 20) | (run << 14) | (1 << 13) | ((-(int32_t)level & 0xfff) << 1) | 1;
								coeff_VLC[intra][last][offset - level][run].len = 30;
							}
							continue;
						}
					}

					coeff_VLC[intra][last][level + offset][run].code
						= (escape << coeff_VLC[intra][last][level_esc + offset][run_esc].len)
						|  coeff_VLC[intra][last][level_esc + offset][run_esc].code;
					coeff_VLC[intra][last][level + offset][run].len
						= coeff_VLC[intra][last][level_esc + offset][run_esc].len + escape_len;

					if (!intra) {
						coeff_VLC[intra][last][offset - level][run].code
							= (escape << coeff_VLC[intra][last][level_esc + offset][run_esc].len)
							|  coeff_VLC[intra][last][level_esc + offset][run_esc].code | 1;
						coeff_VLC[intra][last][offset - level][run].len
							= coeff_VLC[intra][last][level_esc + offset][run_esc].len + escape_len;
					}
				}

				if (!intra) {
					coeff_VLC[intra][last][0][run].code
						= (ESCAPE3 << 21) | (last << 20) | (run << 14) | (1 << 13) | ((-32 & 0xfff) << 1) | 1;
					coeff_VLC[intra][last][0][run].len = 30;
				}
			}
		}
	}

	/* init sprite_trajectory tables
	 * even if GMC is not specified (it might be used later...) */

	sprite_trajectory_code[0+16384].code = 0;
	sprite_trajectory_code[0+16384].len = 0;
	for (k=0;k<14;k++) {
		int limit = (1<<k);

		for (l=-(2*limit-1); l <= -limit; l++) {
			sprite_trajectory_code[l+16384].code = (2*limit-1)+l;
			sprite_trajectory_code[l+16384].len = k+1;
		}

		for (l=limit; l<= 2*limit-1; l++) {
			sprite_trajectory_code[l+16384].code = l;
			sprite_trajectory_code[l+16384].len = k+1;
		}
	}
}




/* returns the number of bits required to encode qcoeff */



static const int iDQtab[5] = {
	1, 0, -1 /* no change */, 2, 3
};
#define DQ_VALUE2INDEX(value)  iDQtab[(value)+2]




/***************************************************************
 * decoding stuff starts here                                  *
 ***************************************************************/


/*
 * for IVOP addbits == 0
 * for PVOP addbits == fcode - 1
 * for BVOP addbits == max(fcode,bcode) - 1
 * returns true or false
 */
int
check_resync_marker(Bitstream * bs, int addbits)
{
	uint32_t nbits;
	uint32_t code;
	uint32_t nbitsresyncmarker = NUMBITS_VP_RESYNC_MARKER + addbits;

	nbits = BitstreamNumBitsToByteAlign(bs);
	code = BitstreamShowBits(bs, nbits);

	if (code == (((uint32_t)1 << (nbits - 1)) - 1))
	{
		return BitstreamShowBitsFromByteAlign(bs, nbitsresyncmarker) == RESYNC_MARKER;
	}

	return 0;
}



int
get_mcbpc_intra(Bitstream * bs)
{

	uint32_t index;

	index = BitstreamShowBits(bs, 9);
	index >>= 3;

	BitstreamSkip(bs, mcbpc_intra_table[index].len);

	return mcbpc_intra_table[index].code;

}

int
get_mcbpc_inter(Bitstream * bs)
{

	uint32_t index;

	index = MIN(BitstreamShowBits(bs, 9), 256);

	BitstreamSkip(bs, mcbpc_inter_table[index].len);

	return mcbpc_inter_table[index].code;

}

int
get_cbpy(Bitstream * bs,
		 int intra)
{

	int cbpy;
	uint32_t index = BitstreamShowBits(bs, 6);

	BitstreamSkip(bs, cbpy_table[index].len);
	cbpy = cbpy_table[index].code;

	if (!intra)
		cbpy = 15 - cbpy;

	return cbpy;

}

static __inline int
get_mv_data(Bitstream * bs)
{

	uint32_t index;

	if (BitstreamGetBit(bs))
		return 0;

	index = BitstreamShowBits(bs, 12);

	if (index >= 512) {
		index = (index >> 8) - 2;
		BitstreamSkip(bs, TMNMVtab0[index].len);
		return TMNMVtab0[index].code;
	}

	if (index >= 128) {
		index = (index >> 2) - 32;
		BitstreamSkip(bs, TMNMVtab1[index].len);
		return TMNMVtab1[index].code;
	}

	index -= 4;

	BitstreamSkip(bs, TMNMVtab2[index].len);
	return TMNMVtab2[index].code;

}

int
get_mv(Bitstream * bs,
	   int fcode)
{

	int data;
	int res;
	int mv;
	int scale_fac = 1 << (fcode - 1);

	data = get_mv_data(bs);

	if (scale_fac == 1 || data == 0)
		return data;

	res = BitstreamGetBits(bs, fcode - 1);
	mv = ((abs(data) - 1) * scale_fac) + res + 1;

	return data < 0 ? -mv : mv;

}

int
get_dc_dif(Bitstream * bs,
		   uint32_t dc_size)
{

	int code = BitstreamGetBits(bs, dc_size);
	int msb = code >> (dc_size - 1);

	if (msb == 0)
		return (-1 * (code ^ ((1 << dc_size) - 1)));

	return code;

}

int
get_dc_size_lum(Bitstream * bs)
{

	int code, i;

	code = BitstreamShowBits(bs, 11);

	for (i = 11; i > 3; i--) {
		if (code == 1) {
			BitstreamSkip(bs, i);
			return i + 1;
		}
		code >>= 1;
	}

	BitstreamSkip(bs, dc_lum_tab[code].len);
	return dc_lum_tab[code].code;

}


int
get_dc_size_chrom(Bitstream * bs)
{

	uint32_t code, i;

	code = BitstreamShowBits(bs, 12);

	for (i = 12; i > 2; i--) {
		if (code == 1) {
			BitstreamSkip(bs, i);
			return i;
		}
		code >>= 1;
	}

	return 3 - BitstreamGetBits(bs, 2);

}

#define GET_BITS(cache, n) ((cache)>>(32-(n)))

static __inline int
get_coeff(Bitstream * bs,
		  int *run,
		  int *last,
		  int intra,
		  int short_video_header)
{

	uint32_t mode;
	int32_t level;
	REVERSE_EVENT *reverse_event;

	uint32_t cache = BitstreamShowBits(bs, 32);
	
	if (short_video_header)		/* inter-VLCs will be used for both intra and inter blocks */
		intra = 0;

	if (GET_BITS(cache, 7) != ESCAPE) {
		reverse_event = &DCT3D[intra][GET_BITS(cache, 12)];

		if ((level = reverse_event->event.level) == 0)
			goto error;

		*last = reverse_event->event.last;
		*run  = reverse_event->event.run;

		/* Don't forget to update the bitstream position */
		BitstreamSkip(bs, reverse_event->len+1);

		return (GET_BITS(cache, reverse_event->len+1)&0x01) ? -level : level;
	}

	/* flush 7bits of cache */
	cache <<= 7;

	if (short_video_header) {
		/* escape mode 4 - H.263 type, only used if short_video_header = 1  */
		*last =  GET_BITS(cache, 1);
		*run  = (GET_BITS(cache, 7) &0x3f);
		level = (GET_BITS(cache, 15)&0xff);

		if (level == 0 || level == 128)
			DPRINTF(XVID_DEBUG_ERROR, "Illegal LEVEL for ESCAPE mode 4: %d\n", level);

		/* We've "eaten" 22 bits */
		BitstreamSkip(bs, 22);

		return (level << 24) >> 24;
	}

	if ((mode = GET_BITS(cache, 2)) < 3) {
		const int skip[3] = {1, 1, 2};
		cache <<= skip[mode];

		reverse_event = &DCT3D[intra][GET_BITS(cache, 12)];

		if ((level = reverse_event->event.level) == 0)
			goto error;

		*last = reverse_event->event.last;
		*run  = reverse_event->event.run;

		if (mode < 2) {
			/* first escape mode, level is offset */
			level += max_level[intra][*last][*run];
		} else {
			/* second escape mode, run is offset */
			*run += max_run[intra][*last][level] + 1;
		}
		
		/* Update bitstream position */
		BitstreamSkip(bs, 7 + skip[mode] + reverse_event->len + 1);

		return (GET_BITS(cache, reverse_event->len+1)&0x01) ? -level : level;
	}

	/* third escape mode - fixed length codes */
	cache <<= 2;
	*last =  GET_BITS(cache, 1);
	*run  = (GET_BITS(cache, 7)&0x3f);
	level = (GET_BITS(cache, 20)&0xfff);
	
	/* Update bitstream position */
	BitstreamSkip(bs, 30);

	return (level << 20) >> 20;

  error:
	*run = VLC_ERROR;
	return 0;
}

void
get_intra_block(Bitstream * bs,
				int16_t * block,
				int direction,
				int coeff)
{

	const uint16_t *scan = scan_tables[direction];
	int level, run, last;

	do {
		level = get_coeff(bs, &run, &last, 1, 0);
		if (run == -1) {
			DPRINTF(XVID_DEBUG_ERROR,"fatal: invalid run");
			break;
		}
		coeff += run;
		
#ifdef _DEBUG
		if(coeff>=64) {
		  DPRINTF(XVID_DEBUG_ERROR,"error: overflow in coefficient index\n");
		  return;
		}
#endif

		block[scan[coeff]] = level;

		DPRINTF(XVID_DEBUG_COEFF,"block[%i] %i\n", scan[coeff], level);
#if 0
		DPRINTF(XVID_DEBUG_COEFF,"block[%i] %i %08x\n", scan[coeff], level, BitstreamShowBits(bs, 32));
#endif

		if (level < -2047 || level > 2047) {
			DPRINTF(XVID_DEBUG_ERROR,"warning: intra_overflow %i\n", level);
		}
		coeff++;
	} while (!last);

}

void
get_inter_block_h263(
		Bitstream * bs,
		int16_t * block,
		int direction,
		const int quant,
		const uint16_t *matrix)
{

	const uint16_t *scan = scan_tables[direction];
	const uint16_t quant_m_2 = quant << 1;
	const uint16_t quant_add = (quant & 1 ? quant : quant - 1);
	int p;
	int level;
	int run;
	int last;

	p = 0;
	do {
		level = get_coeff(bs, &run, &last, 0, 0);
		if (run == -1) {
			DPRINTF(XVID_DEBUG_ERROR,"fatal: invalid run");
			break;
		}
		p += run;

#ifdef _DEBUG
		if(p>=64)	{
		  DPRINTF(XVID_DEBUG_ERROR,"error: overflow in coefficient index\n");
		  return;
		}
#endif

		if (level < 0) {
			level = level*quant_m_2 - quant_add;
			block[scan[p]] = (level >= -2048 ? level : -2048);