ffmpeg.c:1268: error: Null Dereference
  pointer `vstats_file` last assigned on line 1258 could be null and is dereferenced by call to `fprintf()` at line 1268, column 9.

ffmpeg.c:1249:1: start of procedure do_video_stats()
1247. }
1248. 
1249. static void do_video_stats(AVFormatContext *os, AVOutputStream *ost,
      ^
1250.                            int frame_size)
1251. {

ffmpeg.c:1257:10: Taking true branch
1255. 
1256.     /* this is executed just the first time do_video_stats is called */
1257.     if (!vstats_file) {
               ^
1258.         vstats_file = fopen(vstats_filename, "w");
1259.         if (!vstats_file) {

ffmpeg.c:1258:9: 
1256.     /* this is executed just the first time do_video_stats is called */
1257.     if (!vstats_file) {
1258.         vstats_file = fopen(vstats_filename, "w");
              ^
1259.         if (!vstats_file) {
1260.             perror("fopen");

ffmpeg.c:1259:14: Taking true branch
1257.     if (!vstats_file) {
1258.         vstats_file = fopen(vstats_filename, "w");
1259.         if (!vstats_file) {
                   ^
1260.             perror("fopen");
1261.             ffmpeg_exit(1);

ffmpeg.c:1260:13: 
1258.         vstats_file = fopen(vstats_filename, "w");
1259.         if (!vstats_file) {
1260.             perror("fopen");
                  ^
1261.             ffmpeg_exit(1);
1262.         }

ffmpeg.c:1261:13: Skipping ffmpeg_exit(): empty list of specs
1259.         if (!vstats_file) {
1260.             perror("fopen");
1261.             ffmpeg_exit(1);
                  ^
1262.         }
1263.     }

ffmpeg.c:1265:5: 
1263.     }
1264. 
1265.     enc = ost->st->codec;
          ^
1266.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
1267.         frame_number = ost->frame_number;

ffmpeg.c:1266:9: Taking true branch
1264. 
1265.     enc = ost->st->codec;
1266.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
              ^
1267.         frame_number = ost->frame_number;
1268.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);

ffmpeg.c:1267:9: 
1265.     enc = ost->st->codec;
1266.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
1267.         frame_number = ost->frame_number;
              ^
1268.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
1269.         if (enc->flags&CODEC_FLAG_PSNR)

ffmpeg.c:1268:9: 
1266.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
1267.         frame_number = ost->frame_number;
1268.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
              ^
1269.         if (enc->flags&CODEC_FLAG_PSNR)
1270.             fprintf(vstats_file, "PSNR= %6.2f ", psnr(enc->coded_frame->error[0]/(enc->width*enc->height*255.0*255.0)));
