Is it meaningful to raise frame rate, if so what is the best option?

Question

I have a 3000 by 3000 VR video encoded in H264, the frame rate is 30fps. Now I want to raise the frame rate to 60fps, I am using this command

ffmpeg -i input.mp4 -r 60 output.mp4

My questions are:

1. Is it meaningful to raise the frame rate?
2. What is the mechanism of -r 60 in the above command? Since there are only 30 frames per second in the original video, where do those additional 30 frames come from?
3. Is there any better option other than the above command to 'smoothly' raise the fps?

Answer 1

Is it meaningful to raise the frame rate?

Usually, no. Exceptions are if you need to artificially generate slow motion using a robust tool like Twixtor.

What is the mechanism of -r 60 in the above command? Since there are only 30 frames per second in the original video, where do those additional 30 frames come from?

They are simply duplicates of existing frames. Without the use of specific filters, ffmpeg can only duplicate or drop frames when the framerate is changed.

Is there any better option other than the above command to 'smoothly' raise the fps?

ffmpeg now has a motion interpolation filter, which will generate new frames. It can also just do a regular blend if that mode is chosen.

ffmpeg -i in.mp4 -vf minterpolate=fps=60 out.mp4

Answer 2

No, all it will do is waste space and lower the quality of your video. In theory, it shouldn't take too much additional space as the frames will be 100% copies of the previous frame, but it still will have to re-encode and that re-encode will be another generation of quality loss, which could be significant depending on how compressed your video is already.

Using a higher frame rate only really makes sense if you want to either speed up footage or can actually capture at a higher frame rate. Increasing the frame rate will either cause the video to take half as long or will invent new frames to fill in between frames. Exact methods for doing this vary, but frame blending or pull downs where certain frames are duplicated and others not are typical when it isn't an even multiple.

There isn't a better option for increasing it than an even multiple increase, but unless you have some specific reason to need to increase it, it gives you no value as the same thing can be done at run time when playing the video back.

Answer 3

It can be useful to raise the Frame Rate if you use expensive Software and get excellent results, then you can replay the double-rate video at half speed to get slow-motion or play it at full speed to get smoother motion - simply copying each Frame serves little or no purpose and blurring two Frames to create the intermediate Frame is not a somewhat identical result but a different (possibly desirable) result.

Short of paying a lot of money and making a large effort there are numerous Solutions which rely on AviSynth (you can use Search Tools to find lots of Info).

A couple of the 'best' (cheap/easy/great) methods are to use MSU's Tools: http://www.compression.ru/video/frame_rate_conversion/index_en_msu.html or MVTools http://avisynth.org.ru/mvtools/mvtools.html .

While you won't get pixel peeking perfect results you should expect 'great' results with little effort and no cost.

There are examples on those Webpages and Search Engines will provide more than we could reasonably teach you here. If you have a specific question once you've setup give us a shout.