Quote:
Originally Posted by Nintendo Maniac 64
To be honest, I don't really know how to do so either, so I do it the manual way via trial and error - I import the videostream into mkvtoolnix, set the frame rate to something (like 20p), export to an mkv with the new framerate, and then see if can playback this new mkv smoothly without any stutter.
If it does stutter, then I do the exact same process again but with a lower framerate (like 15p).
If it plays without any stutter, then I still do the exact same process again but with a higher framerate.
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That's a pretty good process given the tools available today.
I do note that it might somewhat underestimate SW decoder performance requirements for real-world content significantly.
Slowing down 60p to 30p will result in a stream that may be easier to decode than the same content natively captured at 30p. This is because twice as much motion happens between 30p frames, so there's more prediction and motion vectors per frame to process. Also, the bitrate will drop by half in a 60-30 conversion, when real-world a 30p might be 70-80% the bitrate of a 60p for the same spatial quality (since twice as much change per frame is being captured).
Of course, if real-world decoder characteristics are understood, rate control techniques like VBV can cap the worst-case decoding times, although at the potential risk of capping maximum quality for difficult segments. We got a little spoiled from the last decade-ish of relatively ubiquitous H.264 HW decoding
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