tmndec.c

视频的h263解码

		break;
	}
	
	
	mb_width = horizontal_size/16;
	mb_height = vertical_size/16;
	coded_picture_width = horizontal_size;
	coded_picture_height = vertical_size;
	chrom_width =  coded_picture_width>>1;
	chrom_height = coded_picture_height>>1;
	blk_cnt = 6;
	
	for (cc=0; cc<3; cc++) {//为什么是3呢？？？？？？？？？？？
		if (cc==0)
			size = coded_picture_width*coded_picture_height;
		else
			size = chrom_width*chrom_height;
		
		if (!(refframe[cc] = (unsigned char *)malloc(size)))
			error("malloc failed\n");
		
		if (!(oldrefframe[cc] = (unsigned char *)malloc(size)))
			error("malloc failed\n");
		
		if (!(bframe[cc] = (unsigned char *)malloc(size)))
			error("malloc failed\n");
	}
	
	for (cc=0; cc<3; cc++) {
		if (cc==0) {
			size = (coded_picture_width+64)*(coded_picture_height+64);
			if (!(edgeframeorig[cc] = (unsigned char *)malloc(size)))
				error("malloc failed\n");
			edgeframe[cc] = edgeframeorig[cc] + (coded_picture_width+64) * 32 + 32;
		}
		else {
			size = (chrom_width+32)*(chrom_height+32);
			if (!(edgeframeorig[cc] = (unsigned char *)malloc(size)))
				error("malloc failed\n");
			edgeframe[cc] = edgeframeorig[cc] + (chrom_width+32) * 16 + 16;
		}
	}
	
	if (expand) {
		for (cc=0; cc<3; cc++) {
			if (cc==0)
				size = coded_picture_width*coded_picture_height*4;
			else
				size = chrom_width*chrom_height*4;
			
			if (!(exnewframe[cc] = (unsigned char *)malloc(size)))
				error("malloc failed\n");
		}
	}
	
	/* Clear output file for concatenated storing */
	if (outtype == T_YUV_CONC) {//得到正常的命令清空文件
		if ((cleared = fopen(outputname,"wb")) == NULL) 
			error("couldn't clear outputfile\n");
		else
			fclose(cleared);
	}
	/* IDCT */
	if (refidct)
		init_idctref();
	else
		init_idct();
	
#ifdef DISPLAY
	if (outtype==T_X11) {
		init_display("");
	}
#endif
#ifdef WINDOWS
	if (outtype==T_WIN) {
		initDisplay(coded_picture_width, coded_picture_height);
	}
#endif
	
	
}

void error(text)
char *text;
{
	fprintf(stderr,text);
	exit(1);
}
//出错处理程序

/* trace output */
void printbits(code,bits,len)
int code,bits,len;
{
	int i;
	for (i=0; i<len; i++)
		printf("%d",(code>>(bits-1-i))&1);
}

/* option processing */
static void options(argcp,argvp)//处理输入的命令行
int *argcp;
char **argvp[];
{
	while (*argcp>1 && (*argvp)[1][0]=='-')
	{
		while ((*argvp)[1][1])
		{
			switch (toupper((*argvp)[1][1]))
			{
#ifdef USE_TIME
			case 'F':
				framerate = getval(*argvp);
				break;
#endif
			case 'V':
				verbose = getval(*argvp);
				break;
			case 'O':
				outtype = getval(*argvp);//确定输出的格式
				break;
			case 'R':
				refidct = 1;
				break;
			case 'L':
				loopflag = 1;//若执行此命令则输出分立的.y .u .v文件
				break;
			case 'X':
				expand = 1;
				break;
			case 'T':
				trace = 1;
				break;
			case 'Q':
				quiet = 1;
				break;
			default:
				fprintf(stderr,"undefined option -%c ignored\n",(*argvp)[1][1]);
			}
			
			(*argvp)[1]++;
		}
		
		(*argvp)++;
		(*argcp)--;
	}
	
	
	if (outtype != T_X11 && outtype != T_WIN) {
		loopflag = 0;  /* No looping for output to file */
		//如果给出的输出类型outtype==0即设loopflag = 0可以正常执行解码过程
#ifdef USE_TIME
		framerate = 0; /* No delay necessary when output to file */
#endif
	}
#ifdef DISPLAY
	if (outtype==T_X11)
	{
		(*argcp)++; /* fake outfile parameter */
	}
#endif
#ifdef WINDOWS
	if (outtype==T_WIN)
	{
		(*argcp)++; /* fake outfile parameter */
	}
#endif
//以上是对输出类型即是否解码成yuv文件	
	if (*argcp!=3 && *argcp!=4)//对命令的出错处理
	{
		printf("\n%s\n",version);
		printf("Usage:   tmndecode {options} bitstream {outputfilename%%d}\n\
			   Options: -vn  verbose output (n: level)\n\
			   -on  output format \n\
			   n=0 : YUV\n\
			   n=1 : SIF\n\
			   n=2 : TGA\n\
			   n=3 : PPM\n");
#ifdef DISPLAY
			   printf("\
				   n=4 : X11 Display\n");
#endif
				   printf("\
					   n=5 : YUV concatenated\n");
#ifdef WINDOWS
					   printf("\
						   n=6 : Windows 95/NT Display\n");
#endif
						   printf("\
								  You have to choose one output format!\n\
								  -q   disable warnings to stderr\n\
								  -r   use double precision reference IDCT\n\
								  -t   enable low level tracing\n");
#ifdef DISPLAY
								  printf("\
									  -x   interpolate pictures to double size before display\n");
#endif
#ifdef USE_TIME
									  printf("\
											 -fn  frame rate\n\
											 n=0  : as fast as possible\n\
											 n=99 : read frame rate from bitstream (default)\n");
#endif    
#ifdef DISPLAY
											 printf("\
												 -l   loop sequence\n");
#endif
											 exit(0);
	}
}//命令出错则不进行解码，直接返回

static int getval(argv)
char *argv[];
{
	int val;
	if (sscanf(argv[1]+2,"%d",&val)!=1)
		return 0;
	
	while (isdigit(argv[1][2]))
		argv[1]++;
	
	return val;
}



#ifdef USE_TIME
#ifndef WINDOWS

/* Unix version */
void doframerate(int pb)
{
	struct timeval tfdiff;
	const float REF_FRAME_RATE = 29.97;
	
	/* Compute desired frame rate */
	if (framerate <= 0)
		return;
	
	if (framerate != 99) {
		tftarget.tv_usec += 1000000 / framerate;
	}
	else {
		if (pb) {
			tftarget.tv_usec += 1000000 / (REF_FRAME_RATE/trb);
		}
		else {
			tftarget.tv_usec += 1000000 / (REF_FRAME_RATE/(trd-trb));
		}
	}
	
	/* this is where we should be */
	if (tftarget.tv_usec >= 1000000)
	{
		tftarget.tv_usec -= 1000000;
		tftarget.tv_sec++;
	}
	
	/* this is where we are */
	gettimeofday(&tfdiff,(struct timezone *)NULL);
	
	tfdiff.tv_usec = tftarget.tv_usec - tfdiff.tv_usec;
	tfdiff.tv_sec  = tftarget.tv_sec  - tfdiff.tv_sec;
	if (tfdiff.tv_usec < 0)
	{
		tfdiff.tv_usec += 1000000;
		tfdiff.tv_sec--;
	}
	
	/* See if we are already lagging behind */
	if (tfdiff.tv_sec < 0 || (tfdiff.tv_sec == 0 && tfdiff.tv_usec <= 0))
		return;
	
	/* Spin for awhile */
	select(0,NULL,NULL,NULL,&tfdiff);
}

#else 

/* Win32 version */
void doframerate(int pb)
{
	DWORD currentTime;
	int diffTime;
	const float REF_FRAME_RATE = (float)29.97;
	
	/* Compute desired frame rate */
	//估算帧频
	if (framerate <= 0)
		return;
	
	if (framerate != 99) {
		targetTime += 1000 / framerate;
	}
	else {
		if (pb) {
			targetTime += (int)(1000 / (REF_FRAME_RATE/trb));
		}
		else {
			targetTime += (int)(1000 / (REF_FRAME_RATE/(trd-trb)));
		}
	}
	
	/* this is where we are */
	currentTime = timeGetTime();
	
	
	diffTime = targetTime - currentTime;
	
	/* See if we are already lagging behind */
	if (diffTime <= 0)
		return;
	
	/* Spin for awhile */
	Sleep(diffTime);   
	/* this is not a very accurate timer */
}

#endif

#endif