We have a large video file that we need to annotate. Because viper handles mpegs we used ffmpeg to turn our .avi file into a .mpg. Anyway, at 1100x1100 viper-gt was not able to read the file correctly, at 1026x1026 it was able to read the file correctly. We didn't find the exact number where is stopped because it was a pain, but it is between 1026x1026 and 1100x1100. The video file plays in VLC regardless, so it is not ffmpeg.