学步园

      在ldecod.c文件的main中调用了init_conf函数，这个函数实际上就实现了程序从配置文件读数据的过程. 之前说过，在JM8.6编码端，Configure函数起着做配置文件encoder_baseline.cfg数据的作用，现在来看看解码端的init_conf函数.

      main中是这样调用的：

init_conf(input, argv[1]);

     其中input是一个结构体指针，字符串指针argv[1]实际上就指向了字符串"decoder.cfg", 进入init_conf函数看看：

void init_conf(struct inp_par *inp,
               char *config_filename)
{
  FILE *fd;
  int NAL_mode;

  // read the decoder configuration file
  if((fd=fopen(config_filename,"r")) == NULL)
  {
    snprintf(errortext, ET_SIZE, "Error: Control file %s not found\n",config_filename);
    error(errortext, 300);
  }

  fscanf(fd,"%s",inp->infile);                // H.264 compressed input bitsream
  
  // 过滤配置文件中的“注释”
  fscanf(fd,"%*[^\n]");

  fscanf(fd,"%s",inp->outfile);               // YUV 4:2:2 input format
  fscanf(fd,"%*[^\n]");

  fscanf(fd,"%s",inp->reffile);               // reference file
  fscanf(fd,"%*[^\n]");


  // Frame buffer size
  fscanf(fd,"%d,",&inp->dpb_size);   // may be overwritten in case of RTP NAL
  fscanf(fd,"%*[^\n]");
  if (inp->dpb_size < 1)
  {
    snprintf(errortext, ET_SIZE, "Decoded Picture Buffer Size is %d. It has to be at least 1",inp->dpb_size);
    error(errortext,1);
  }

  fscanf(fd,"%d",&(NAL_mode));                // NAL mode
    fscanf(fd,"%*[^\n]");

  switch(NAL_mode)
  {
  case 0:
    inp->FileFormat = PAR_OF_ANNEXB;
    break;
  case 1:
    inp->FileFormat = PAR_OF_RTP;
    break;
  default:
    snprintf(errortext, ET_SIZE, "NAL mode %i is not supported", NAL_mode);
    error(errortext,400);
  }

  fscanf(fd,"%d,",&inp->ref_offset);   // offset used for SNR computation
  fscanf(fd,"%*[^\n]");

  fscanf(fd,"%d,",&inp->poc_scale);   // offset used for SNR computation
  fscanf(fd,"%*[^\n]");


  if (inp->poc_scale < 1 || inp->poc_scale > 2)
  {
    snprintf(errortext, ET_SIZE, "Poc Scale is %d. It has to be 1 or 2",inp->poc_scale);
    error(errortext,1);
  }

#ifdef _LEAKYBUCKET_
  fscanf(fd,"%ld,",&inp->R_decoder);             // Decoder rate
  fscanf(fd, "%*[^\n]");
  fscanf(fd,"%ld,",&inp->B_decoder);             // Decoder buffer size
  fscanf(fd, "%*[^\n]");
  fscanf(fd,"%ld,",&inp->F_decoder);             // Decoder initial delay
  fscanf(fd, "%*[^\n]"); 
  fscanf(fd,"%s",inp->LeakyBucketParamFile);    // file where Leaky Bucket params (computed by encoder) are stored
  fscanf(fd,"%*[^\n]");
#endif

  fclose (fd);


#if TRACE
  if ((p_trace=fopen(TRACEFILE,"w"))==0)             // append new statistic at the end
  {
    snprintf(errortext, ET_SIZE, "Error open file %s!",TRACEFILE);
    error(errortext,500);
  }
#endif


  if ((p_out=fopen(inp->outfile,"wb"))==0)
  {
    snprintf(errortext, ET_SIZE, "Error open file %s ",inp->outfile);
    error(errortext,500);
  }
/*  if ((p_out2=fopen("out.yuv","wb"))==0)
  {
    snprintf(errortext, ET_SIZE, "Error open file %s ",inp->outfile);
    error(errortext,500);
  }*/

  fprintf(stdout,"--------------------------------------------------------------------------\n");
  fprintf(stdout," Decoder config file                    : %s \n",config_filename);
  fprintf(stdout,"--------------------------------------------------------------------------\n");
  fprintf(stdout," Input H.264 bitstream                  : %s \n",inp->infile);
  fprintf(stdout," Output decoded YUV 4:2:0               : %s \n",inp->outfile);
  fprintf(stdout," Output status file                     : %s \n",LOGFILE);
  if ((p_ref=fopen(inp->reffile,"rb"))==0)
  {
    fprintf(stdout," Input reference file                   : %s does not exist \n",inp->reffile);
    fprintf(stdout,"                                          SNR values are not available\n");
  }
  else
    fprintf(stdout," Input reference file                   : %s \n",inp->reffile);

  fprintf(stdout,"--------------------------------------------------------------------------\n");
#ifdef _LEAKYBUCKET_
  fprintf(stdout," Rate_decoder        : %8ld \n",inp->R_decoder);
  fprintf(stdout," B_decoder           : %8ld \n",inp->B_decoder);
  fprintf(stdout," F_decoder           : %8ld \n",inp->F_decoder);
  fprintf(stdout," LeakyBucketParamFile: %s \n",inp->LeakyBucketParamFile); // Leaky Bucket Param file
  calc_buffer(inp);
  fprintf(stdout,"--------------------------------------------------------------------------\n");
#endif
  fprintf(stdout,"POC must = frame# or field# for SNRs to be correct\n");
  fprintf(stdout,"Frame    POC   QP  SnrY    SnrU    SnrV   Time(ms)\n");
}

       可见，通过调用init_conf函数，实际上就是把argv[1]对应的配置文件的数据往input对应的结构体中倾倒，像倒茶一般， 这样，程序中的全局的指针变量对应的结构体就获得了配置文件encoder.cfg中的数据.

       最后，附带给出配置文件encoder.cfg中的内容:

test.264                 ........H.264 coded bitstream
test_dec.yuv             ........Output file, YUV 4:2:0 format
test_rec.yuv             ........Ref sequence (for SNR)
10                       ........Decoded Picture Buffer size
0                        ........NAL mode (0=Annex B, 1: RTP packets)
0                        ........SNR computation offset
1                        ........Poc Scale (1 or 2)
500000                   ........Rate_Decoder
104000                   ........B_decoder
73000                    ........F_decoder
leakybucketparam.cfg     ........LeakyBucket Params

This is a file containing input parameters to the JVT H.264/AVC decoder.
The text line following each parameter is discarded by the decoder.