Fail and print correct error message when video stream pixel format

is unknown.

Originally committed as revision 19164 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -1818,6 +1818,10 @@ static int av_encode(AVFormatContext **output_files,
                 ost->encoding_needed = 1;
                 break;
             case CODEC_TYPE_VIDEO:
+                if (ost->st->codec->pix_fmt == PIX_FMT_NONE) {
+                    fprintf(stderr, "Video pixel format is unknown, stream cannot be decoded\n");
+                    av_exit(1);
+                }
                 ost->video_crop = ((frame_leftBand + frame_rightBand + frame_topBand + frame_bottomBand) != 0);
                 ost->video_pad = ((frame_padleft + frame_padright + frame_padtop + frame_padbottom) != 0);
                 ost->video_resample = ((codec->width != icodec->width -