ffmpeg.c:1252: error: Null Dereference
  pointer `vstats_file` last assigned on line 1242 could be null and is dereferenced by call to `fprintf()` at line 1252, column 9.

ffmpeg.c:1233:1: start of procedure do_video_stats()
1231. }
1232. 
1233. static void do_video_stats(AVFormatContext *os, AVOutputStream *ost,
      ^
1234.                            int frame_size)
1235. {

ffmpeg.c:1241:10: Taking true branch
1239. 
1240.     /* this is executed just the first time do_video_stats is called */
1241.     if (!vstats_file) {
               ^
1242.         vstats_file = fopen(vstats_filename, "w");
1243.         if (!vstats_file) {

ffmpeg.c:1242:9: 
1240.     /* this is executed just the first time do_video_stats is called */
1241.     if (!vstats_file) {
1242.         vstats_file = fopen(vstats_filename, "w");
              ^
1243.         if (!vstats_file) {
1244.             perror("fopen");

ffmpeg.c:1243:14: Taking true branch
1241.     if (!vstats_file) {
1242.         vstats_file = fopen(vstats_filename, "w");
1243.         if (!vstats_file) {
                   ^
1244.             perror("fopen");
1245.             ffmpeg_exit(1);

ffmpeg.c:1244:13: 
1242.         vstats_file = fopen(vstats_filename, "w");
1243.         if (!vstats_file) {
1244.             perror("fopen");
                  ^
1245.             ffmpeg_exit(1);
1246.         }

ffmpeg.c:1245:13: Skipping ffmpeg_exit(): empty list of specs
1243.         if (!vstats_file) {
1244.             perror("fopen");
1245.             ffmpeg_exit(1);
                  ^
1246.         }
1247.     }

ffmpeg.c:1249:5: 
1247.     }
1248. 
1249.     enc = ost->st->codec;
          ^
1250.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
1251.         frame_number = ost->frame_number;

ffmpeg.c:1250:9: Taking true branch
1248. 
1249.     enc = ost->st->codec;
1250.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
              ^
1251.         frame_number = ost->frame_number;
1252.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);

ffmpeg.c:1251:9: 
1249.     enc = ost->st->codec;
1250.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
1251.         frame_number = ost->frame_number;
              ^
1252.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
1253.         if (enc->flags&CODEC_FLAG_PSNR)

ffmpeg.c:1252:9: 
1250.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
1251.         frame_number = ost->frame_number;
1252.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
              ^
1253.         if (enc->flags&CODEC_FLAG_PSNR)
1254.             fprintf(vstats_file, "PSNR= %6.2f ", psnr(enc->coded_frame->error[0]/(enc->width*enc->height*255.0*255.0)));
