func: int ff_parse_sample_rate(unsigned *ret, const char *arg, void *log_ctx)
  
  {
  
      char *tail;
  
      double srate = av_strtod(arg, &tail);
  
      if (*tail || srate < 1 || (int)srate != srate) {
  
          av_log(log_ctx, AV_LOG_ERROR, "Invalid sample rate '%s'\n", arg);
  
          return AVERROR(EINVAL);
  
      }
  
      *ret = srate;
  
      return 0;
  
  }
  