mp4_mblock.c

<VC++视频音频开发>一书的光盘资料。

#include <math.h>
#include <assert.h>

#include "mp4_vars.h"

#include "getbits.h"
#include "mp4_block.h"
#include "mp4_mblock.h"
#include "debug.h"

/**
 *
**/

static int getMCBPC();
static int getCBPY();
static int setMV(int block_num);
static int getMVdata();

/***/

extern int find_pmv(int block_num, int type);
extern void addblock (int comp, int bx, int by, int addflag);
extern void addblockIntra (int comp, int bx, int by);
extern void addblockInter (int comp, int bx, int by);

/***/

int macroblock()
{
	int j;
	int intraFlag, interFlag;

	if (mp4_state->hdr.prediction_type != I_VOP)
		mp4_state->hdr.not_coded = getbits(1);

	// 编码宏块或I-VOP
	if (! mp4_state->hdr.not_coded || mp4_state->hdr.prediction_type == I_VOP) {

		mp4_state->hdr.mcbpc = getMCBPC(); 
		mp4_state->hdr.derived_mb_type = mp4_state->hdr.mcbpc & 7;
		mp4_state->hdr.cbpc = (mp4_state->hdr.mcbpc >> 4) & 3;

		mp4_state->modemap[mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = 
			mp4_state->hdr.derived_mb_type; // 仅在P-VOPs时使用
		intraFlag = ((mp4_state->hdr.derived_mb_type == INTRA) || 
			(mp4_state->hdr.derived_mb_type == INTRA_Q)) ? 1 : 0;
		interFlag = (! intraFlag);

		if (intraFlag)
			mp4_state->hdr.ac_pred_flag = getbits(1);
		if (mp4_state->hdr.derived_mb_type != STUFFING) {

			mp4_state->hdr.cbpy = getCBPY(); 
			mp4_state->hdr.cbp = (mp4_state->hdr.cbpy << 2) | mp4_state->hdr.cbpc;
		}
		else
			return 1;

		if (mp4_state->hdr.derived_mb_type == INTER_Q ||
			mp4_state->hdr.derived_mb_type == INTRA_Q) {

			mp4_state->hdr.dquant = getbits(2);
			mp4_state->hdr.quantizer += DQtab[mp4_state->hdr.dquant];
			if (mp4_state->hdr.quantizer > 31)
				mp4_state->hdr.quantizer = 31;
			else if (mp4_state->hdr.quantizer < 1)
				mp4_state->hdr.quantizer = 1;
		}
		if (mp4_state->hdr.derived_mb_type == INTER ||
			mp4_state->hdr.derived_mb_type == INTER_Q) {

			setMV(-1); 
		}
		else if (mp4_state->hdr.derived_mb_type == INTER4V) {

			for (j = 0; j < 4; j++) {

				setMV(j); 
			}
		}
		else { 
			if (mp4_state->hdr.prediction_type == P_VOP) {
				int i;
				for (i = 0; i < 4; i++) {
					mp4_state->MV[0][i][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = 0;
					mp4_state->MV[1][i][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = 0;
				}
			}
		}

		// 运动补偿
		if (interFlag) 
		{
			reconstruct(mp4_state->hdr.mb_xpos, mp4_state->hdr.mb_ypos, mp4_state->hdr.derived_mb_type);

			// 纹理解码
			for (j = 0; j < 6; j++) {
				int coded = mp4_state->hdr.cbp & (1 << (5 - j));

				if (coded) { 
					blockInter(j, (coded != 0));
					addblockInter(j, mp4_state->hdr.mb_xpos, mp4_state->hdr.mb_ypos);
				}
			}
		}
		else 
		{
			// 纹理解码
			for (j = 0; j < 6; j++) {
				int coded = mp4_state->hdr.cbp & (1 << (5 - j));

				blockIntra(j, (coded != 0));
				addblockIntra(j, mp4_state->hdr.mb_xpos, mp4_state->hdr.mb_ypos);
			}
		}
	}

	// 没编码的宏块
	else {

		mp4_state->MV[0][0][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = mp4_state->MV[0][1][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] =
		mp4_state->MV[0][2][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = mp4_state->MV[0][3][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = 0;
		mp4_state->MV[1][0][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = mp4_state->MV[1][1][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] =
		mp4_state->MV[1][2][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = mp4_state->MV[1][3][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = 0;

		mp4_state->modemap[mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = NOT_CODED; // [Review] used only in P-VOPs

		reconstruct(mp4_state->hdr.mb_xpos, mp4_state->hdr.mb_ypos, mp4_state->hdr.derived_mb_type);
	}

	mp4_state->quant_store[mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = mp4_state->hdr.quantizer;

	if (mp4_state->hdr.mb_xpos < (mp4_state->mb_width-1)) {
		mp4_state->hdr.mb_xpos++;
	}
	else {
		mp4_state->hdr.mb_ypos++;
		mp4_state->hdr.mb_xpos = 0;
	}

	return 1;
}

/***/

static int getMCBPC()
{
	if (mp4_state->hdr.prediction_type == I_VOP)
	{
		int code = showbits(9);

		if (code == 1) {
			flushbits(9); // 填充
			return 0;
		}
		else if (code < 8) {
			return -1;
		}

		code >>= 3;
		if (code >= 32) {
			flushbits(1);
			return 3;
		}
		
		flushbits(mp4_tables->MCBPCtabIntra[code].len);
		return mp4_tables->MCBPCtabIntra[code].val;
	}
	else
	{
		int code = showbits(9);

		if (code == 1) {
			flushbits(9); // 填充
			return 0;
		}
		else if (code == 0)	{
			return -1;
		}
		
		if (code >= 256)
		{
			flushbits(1);
			return 0;
		}
		
		flushbits(mp4_tables->MCBPCtabInter[code].len);
		return mp4_tables->MCBPCtabInter[code].val;
	}
}

/***/

static int getCBPY()
{
	int cbpy;
	int code = showbits(6);

	if (code < 2) {
		return -1;
	}
			  
	if (code >= 48) {
		flushbits(2);
		cbpy = 15;
	} else {
		flushbits(mp4_tables->CBPYtab[code].len);
		cbpy = mp4_tables->CBPYtab[code].val;
	}

	if (!((mp4_state->hdr.derived_mb_type == 3) ||
		(mp4_state->hdr.derived_mb_type == 4)))
		  cbpy = 15 - cbpy;

  return cbpy;
}

/***/

static int setMV(int block_num)
{
	int hor_mv_data, ver_mv_data, hor_mv_res, ver_mv_res;
	int scale_fac = 1 << (mp4_state->hdr.fcode_for - 1);
	int high = (32 * scale_fac) - 1;
	int low = ((-32) * scale_fac);
	int range = (64 * scale_fac);

	int mvd_x, mvd_y, pmv_x, pmv_y, mv_x, mv_y;	

  hor_mv_data = getMVdata(); 

	if ((scale_fac == 1) || (hor_mv_data == 0))
		mvd_x = hor_mv_data;
	else {
		hor_mv_res = getbits(mp4_state->hdr.fcode_for-1); // mv residual
		mvd_x = ((abs(hor_mv_data) - 1) * scale_fac) + hor_mv_res + 1;
		if (hor_mv_data < 0)
			mvd_x = - mvd_x;
	}

  ver_mv_data = getMVdata(); 

	if ((scale_fac == 1) || (ver_mv_data == 0))
		mvd_y = ver_mv_data;
	else {
		ver_mv_res = getbits(mp4_state->hdr.fcode_for-1);
		mvd_y = ((abs(ver_mv_data) - 1) * scale_fac) + ver_mv_res + 1;
		if (ver_mv_data < 0)
			mvd_y = - mvd_y;
	}

	if (block_num == -1) {
		pmv_x = find_pmv(0, 0);
		pmv_y = find_pmv(0, 1);
	}
	else {
		pmv_x = find_pmv(block_num, 0);
		pmv_y = find_pmv(block_num, 1);
	}


	mv_x = pmv_x + mvd_x;

	if (mv_x < low)
		mv_x += range;
	if (mv_x > high)
		mv_x -= range;

	mv_y = pmv_y + mvd_y;

	if (mv_y < low)
		mv_y += range;
	if (mv_y > high)
		mv_y -= range;


	if (block_num == -1) {
		int i;
		for (i = 0; i < 4; i++) {
			mp4_state->MV[0][i][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = mv_x;
			mp4_state->MV[1][i][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = mv_y;
		}
	}
	else {
		mp4_state->MV[0][block_num][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = mv_x;
		mp4_state->MV[1][block_num][mp4_state->hdr.mb_ypos+1][mp4_state->hdr.mb_xpos+1] = mv_y;
	}

  return 1;
}

/***/

static int getMVdata()
{
	int code;

	if (getbits(1)) {
		return 0; 
  }
	
	code = showbits(12);

	if (code >= 512)
  {
		code = (code >> 8) - 2;
		flushbits(mp4_tables->MVtab0[code].len);
		return mp4_tables->MVtab0[code].val;
  }
	
	if (code >= 128)
  {
		code = (code >> 2) - 32;
		flushbits(mp4_tables->MVtab1[code].len);
		return mp4_tables->MVtab1[code].val;
  }

	code -= 4; 

	assert(code >= 0);

	flushbits(mp4_tables->MVtab2[code].len);
	return mp4_tables->MVtab2[code].val;
}

/***/