ffmpeg.c:2696: error: Null Dereference
  pointer `mid` last assigned on line 2696 could be null and is dereferenced at line 2696, column 5.

ffmpeg.c:2688:1: start of procedure opt_metadata()
2686. }
2687. 
2688. static int opt_metadata(const char *opt, const char *arg)
      ^
2689. {
2690.     char *mid= strchr(arg, '=');

ffmpeg.c:2690:5: 
2688. static int opt_metadata(const char *opt, const char *arg)
2689. {
2690.     char *mid= strchr(arg, '=');
          ^
2691. 
2692.     if(!mid){

ffmpeg.c:2692:9: Taking true branch
2690.     char *mid= strchr(arg, '=');
2691. 
2692.     if(!mid){
              ^
2693.         fprintf(stderr, "Missing =\n");
2694.         av_exit(1);

ffmpeg.c:2693:9: 
2691. 
2692.     if(!mid){
2693.         fprintf(stderr, "Missing =\n");
              ^
2694.         av_exit(1);
2695.     }

ffmpeg.c:2694:9: Skipping av_exit(): empty list of specs
2692.     if(!mid){
2693.         fprintf(stderr, "Missing =\n");
2694.         av_exit(1);
              ^
2695.     }
2696.     *mid++= 0;

ffmpeg.c:2696:5: 
2694.         av_exit(1);
2695.     }
2696.     *mid++= 0;
          ^
2697. 
2698.     metadata_count++;
