edit vfr mp4 clips in nle without huge intermediate files

[codemaster]

I get VFR (variable frame rate) mp4 files that I want to edit in a NLE. I get them from screen recording apps and smartphone cameras.

Is there a solution for editing VFR mp4 files in Vegas Pro and Premiere Pro, without transcoding everything to extremely large lossless intermediate files?

I use ffmpeg to convert from VFR to CFR, and to encode to ProRes, but this solution takes too much time, and the mov files are too large.

I could use LosslessCut to trim the VFR clips, and then convert them to CFR. But it would be much better if there was no transcoding required, just like there is no transcoding required with CFR clips.

[ProWo]

You can try clever FFmpeg GUI.
Load your video, click main, click various, click fix timestamps.
You should know the framerate of the video.
With variable framerate you can often see several framerates in mediainfo, e.g. max framerate 24.123, min framerate 22.946 and framerate 23.678.
The correct framerate is probably 23.976.
Enter this in the FPS field and click fix.
The video is copied in streamcopy mode, so the intervention is fast.
You can then import the result into vegas pro or premiere pro and process it further.


[Attachment 75099 - Click to enlarge]

[codemaster]

But this solution of using ffmpeg to recreate timestamps without reencoding, does it have the same result as the solution of using the fps filter in ffmpeg to convert to CFR? Do the same frames get duplicated or dropped for both solutions? Do both solutions prevent audio sync issues?

[ProWo]

But this solution of using ffmpeg to recreate timestamps without reencoding, does it have the same result as the solution of using the fps filter in ffmpeg to convert to CFR? Do the same frames get duplicated or dropped for both solutions? Do both solutions prevent audio sync issues?

No frames are dropped or duplicated.
Audio is not changed and remains synchronized.
It is important to find the correct frame rate.
This is relatively easy with commercial films, which should have 23.976, 24, 25, 29.97 fps.
The problem is often that someone re-encodes such films and makes mistakes in the process.

[codemaster]

So for a mp4 clip created by the camera built into a smartphone, which would be the "correct" frame rate?

For this mp4 clip, MediaInfo returned:

Frame rate mode                          : Variable
Frame rate                               : 29.678 FPS
Minimum frame rate                       : 14.871 FPS
Maximum frame rate                       : 32.040 FPS

And for the same mp4 clip, ffprobe returned:

Stream #0:0[0x1](eng): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p(progressive), 1920x1088, 19390 kb/s, SAR 1:1 DAR 30:17, 29.68 fps, 29.83 tbr, 90k tbn (default)

Is 29.678 the correct fps? Or 29.97? Or 30?

[ProWo]

I would say 29.97 fps.
But you can first simply remux the video to mkv to see the real framerate.

[codemaster]

After remuxing this mp4 to mkv with mkvmerge, mediainfo detects 29.677 fps (instead of 29.678) and ffprobe detects 29.79 fps (instead of 29.68). It's easier to just use the fps filter in ffmpeg to duplicate and drop frames, but the prores files will require 700 GB of free space on HDD.

[ProWo]

After remuxing this mp4 to mkv with mkvmerge, mediainfo detects 29.677 fps (instead of 29.678) and ffprobe detects 29.79 fps (instead of 29.68). It's easier to just use the fps filter in ffmpeg to duplicate and drop frames, but the prores files will require 700 GB of free space on HDD.

Try first my solution with 29.97 fps.

[codemaster]

Eventually, the solution I found and chose, is using a NLE that has support for variable frame rate clips. Such as clips from phone cameras and screen recording apps, that have variable frame rate. So for VFR clips I use a NLE like Camtasia or Movavi, and for CFR clips I use Vegas Pro or Premiere Pro.

Transcoding to ProRes takes too much time, and way too much space. Transcoding to AVC or HEVC is fast if using hardware encoders, doesn't require too much space, but it adds one additional generation of compression. Premiere Pro doesn't support proxy editing for VFR clips, but Movavi does.

So the best way to edit VFR clips is by avoiding pro NLEs and using only non pro NLEs like Movavi, Capcut, PowerDirector, Filmora, Clipchamp, Camtasia.

[rgr]

Vegas supports VFR, but I can't say whether it does it perfectly.

[codemaster]

Vegas Pro supports VFR, but the proxy files have huge file size. Premiere Pro supports VFR and small file size proxy files, but doesn't support proxy editing for VFR. Camtasia records VFR, and edits VFR fast, proving editing VFR is possible and fast. Movavi supports VFR, creates 480p VFR proxy clips that have small file size and decode very fast, and exports 4K fast, encoding with GPU, while CPU only renders. Movavi is the fastest and easiest way to edit VFR, Vegas Pro and Premiere Pro are the slowest. Using pro NLEs to edit phone camera footage is not a good idea in 2024, because all phones record VFR, and because transcoding all footage to ProRes, just to turn it from VFR to CFR, requires more time and drive space than most people have.

[Alwyn]

In my experience, phone video footage is generally of such good quality these days that an encode to high-bitrate CFR H264 will still result in a quite-acceptable file for further editing without requiring a ("huge") lossless intermediate.

[codemaster]

That's true, but if you are someone that is willing to avoid one additional generation of compression, you use a compatible NLE instead of transcoding to high bitrate lossy CFR. Capcut is compatible with phones, Premiere Pro is not. My conclusion: pro camera, pro NLE; phone camera, phone NLE. My problem was that I was insisting on using an incompatible NLE.

[rgr]

Vegas Pro supports VFR, but the proxy files have huge file size.

You don't need to create a proxy file, it's not needed for anything.

because all phones record VFR

Google Pixels don't