ffmpeg.c:3655: error: Null Dereference
  pointer `p` last assigned on line 3655 could be null and is dereferenced at line 3655, column 5.

ffmpeg.c:3640:1: start of procedure opt_streamid()
3638. 
3639. /* arg format is "output-stream-index:streamid-value". */
3640. static void opt_streamid(const char *opt, const char *arg)
      ^
3641. {
3642.     int idx;

ffmpeg.c:3646:5: 
3644.     char idx_str[16];
3645. 
3646.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3647.     idx_str[sizeof(idx_str)-1] = '\0';
3648.     p = strchr(idx_str, ':');

ffmpeg.c:3647:5: 
3645. 
3646.     strncpy(idx_str, arg, sizeof(idx_str));
3647.     idx_str[sizeof(idx_str)-1] = '\0';
          ^
3648.     p = strchr(idx_str, ':');
3649.     if (!p) {

ffmpeg.c:3648:5: 
3646.     strncpy(idx_str, arg, sizeof(idx_str));
3647.     idx_str[sizeof(idx_str)-1] = '\0';
3648.     p = strchr(idx_str, ':');
          ^
3649.     if (!p) {
3650.         fprintf(stderr,

ffmpeg.c:3649:10: Taking true branch
3647.     idx_str[sizeof(idx_str)-1] = '\0';
3648.     p = strchr(idx_str, ':');
3649.     if (!p) {
               ^
3650.         fprintf(stderr,
3651.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3650:9: 
3648.     p = strchr(idx_str, ':');
3649.     if (!p) {
3650.         fprintf(stderr,
              ^
3651.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3652.                 arg, opt);

ffmpeg.c:3653:9: Skipping av_exit(): empty list of specs
3651.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3652.                 arg, opt);
3653.         av_exit(1);
              ^
3654.     }
3655.     *p++ = '\0';

ffmpeg.c:3655:5: 
3653.         av_exit(1);
3654.     }
3655.     *p++ = '\0';
          ^
3656.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3657.     streamid_map[idx] = parse_number_or_die(opt, p, OPT_INT, 0, INT_MAX);
