Making a Variable Frame Rate video

[Mr. Anderssarian]

Yes, you read the title correctly... I want to make a VFR video.

I have completely given up on trying to find a NLE you can edit VFR in, so that's that.

What I haven't given up on is finding a way to create a video that's frame rate will change during its run time.

I've tried the concat filter in FFmpeg. But that just uses the first video's frame rate.
In Vegas I tried 'Allow source to adjust frame rate'. This has VFR in the metadata but the frame rate did not change.

From what I know VFR is supposed to be for Devices/Situations where the frame rate can change (or can not be maintained) whether that be from a camera overheating or a game being played.

If that's the case I would assume that the only way to create VFR video is to do it in real time and feed the encoder frames based on the timing you want.
But real time isn't particularly practical. Coding a render engine for this specific task, No VBR 2-Pass, not to mention the overall quality of what you get going real time.

If anyone has any experience using VFR; please I am all ears.

I thank you for your time reading this and I hope I this is the correct thread.

Anderssarian

[poisondeathray]

The other common situation is for distribution. Fewer frames encoded, slightly reduced bandwidth requirements. Suitable for web delivery in some situtations



1) I'm assuming you want timecode VFR . This means fewer frames are actually encoded, and timecode information controls the speed of playback

Easiest way is probably to use v1 timecodes or timestamps

You just list the ranges and their corresponding framerates in a text file, save it , then either use an encoder that accepts timecode input (e.g. x264) , or use a muxing tool that accepts timecodes (eg. mkvtoolnix, mp4fpsmod etc..)

In this example, the "base" frame rate is 30.0fps, except for the specified ranges 800-1000 are at 24.0fps, 1500-1700 are at 60.0fps

# timecode format v1
assume 30.0
800,1000,24.0
1500,1700,60.0

2) The 2nd other type of VFR is "VFR in CFR" . They are just hardcoded duplicates, giving a cadence . For example, 23.976 "film" in 29.97 telecine. e.g. A NTSC DVD with video and film sections intermixed . This type has more frames encoded, not fewer

3) The 3rd type is soft pulldown . Flags signal repeat fields to give different cadences .

[manono]

AviSynth has been able to help create variable framerate videos for years.

[Mr. Anderssarian]

Thank You very much I will have a look.
I've been finding a lot of useful things in this forum (though only after I posted my question)