ffmpeg.c:2700: error: Null Dereference
  pointer `mid` last assigned on line 2700 could be null and is dereferenced at line 2700, column 5.

ffmpeg.c:2692:1: start of procedure opt_metadata()
2690. }
2691. 
2692. static int opt_metadata(const char *opt, const char *arg)
      ^
2693. {
2694.     char *mid= strchr(arg, '=');

ffmpeg.c:2694:5: 
2692. static int opt_metadata(const char *opt, const char *arg)
2693. {
2694.     char *mid= strchr(arg, '=');
          ^
2695. 
2696.     if(!mid){

ffmpeg.c:2696:9: Taking true branch
2694.     char *mid= strchr(arg, '=');
2695. 
2696.     if(!mid){
              ^
2697.         fprintf(stderr, "Missing =\n");
2698.         av_exit(1);

ffmpeg.c:2697:9: 
2695. 
2696.     if(!mid){
2697.         fprintf(stderr, "Missing =\n");
              ^
2698.         av_exit(1);
2699.     }

ffmpeg.c:2698:9: Skipping av_exit(): empty list of specs
2696.     if(!mid){
2697.         fprintf(stderr, "Missing =\n");
2698.         av_exit(1);
              ^
2699.     }
2700.     *mid++= 0;

ffmpeg.c:2700:5: 
2698.         av_exit(1);
2699.     }
2700.     *mid++= 0;
          ^
2701. 
2702.     metadata_count++;
