Opening mp4 videos with different Frame Rate for Quality Comparison

Hello, Sorry if i have raised the topic which already exists..I have checked the forum - but have not found the answer. The question is the following: I have the MSU VQMT tool which compares the quality of the original and the optimized videos by checking the same frames of each video. And i am faced with the problem of comparison mp4 videos with Variable Frame Rate and Constant Frame Rate. I use the Avisynth script to open mp4 and i can see that program compares the wrong frames: frame of original videos with frame of optimized video, but several seconds later or prior. Therefore i get the wrong results of tool. So the question is: How to open the Original and Optimized variants of MP4 videos with Avisynth script to compare exactly the right frames? The following cases could be: 1) The VFR mp4 is optimized to the VFR mp4 2) The CFR mp4 is optimized to the CFR mp4 3) The VFR mp4 is optimized to the CFR mp4 I assume that for the 1st case files should be opened in the following way: clip = DirectShowSource("D:\Qualitytest\Test\orig\00001-LUjn3RpkcKY.mp4", converfps=true) return clip But original and optimized frames are very shifted. For the second case: clip = DirectShowSource("D:\Qualitytest\Test\orig\video.mp4") framePerSecond=clip.FrameRate clip1 = DirectShowSource("D:\Qualitytest\Test\optimized\video.mp4",fps = framePerSecond) return clip1 The original and optimized frames are almost the same, but not exacly For the 3rd case i even do not know what to do.. PS: I do not know in which way videos have been optimized. But need to compare the right frames and get the results.. Does anybody have any suggestions?:thanks:

You need a frame accurate source filter.

He means indexed and frame accurate like DGNVTools However, if the "optimized VFR" version has different framecount (e.g. decimated duplicates), it won't matter

If at some time in the future you intend to play your .MP4 files via a hardware player. Stick to CFR encodes for compatibility...

ffmpegsource() would be my choice: DDS2() is also frame accurate, but I don't know if its as stable as ffmpegsource. But I think it would be the only option if working with .WMV or some other not well supported proprietary format.