[HELP] Video Profile with Constant FPS?

[pgilfernandez]

How to setup a video export Profile with Constant FPS? well, I don't know if this is what I really need as the problem emerges in Kdenlive where it always tells me that the video (any video rendered by Friction) has variable framerate and must be transcoded to be properly used in the timeline.

Any idea?
Thanks!

[rodlie]

This is a problem in kdenlive, it broke sometime after 24.02.

kdenlive is the only app with this problem, so I blame them 😄

[rodlie]

kdenlive 24.02

kdenlive 24.12

Does not run on my macbook, just crashes 😄 If it worked it would complain about the file.

[pgilfernandez]

Ufff, tricky thing then.
Anyway, if I encode Friction videos with HandBrake and set the "constant FPS" option, the video works perfectly with my Kdenlive version:

This way Kdenlive doesn't complain so there must be something in the Friction FFMPEG output config that Kdenlive doesn't like, right?
That's why I'm looking for the setting that makes Kdenlive love my Friction videos, hehehe.

kdenlive 24.12
Does not run on my macbook, just crashes 😄 If it worked it would complain about the file.

Kdenlive 24.12.0 works fine under macOS Monterey but any newer revision crashes at startup...

[pgilfernandez]

Anyway, could you give me an example on how to correctly use the "advanced options?
Anything I try looks like has no effect:

[rodlie]

This way Kdenlive doesn't complain so there must be something in the Friction FFMPEG output config that Kdenlive doesn't like

Sure, it's something. But it's the only app with this problem and 24.02.x works :)

mediainfo twoday-mograph.mov 
General
Complete name                            : twoday-mograph.mov
Format                                   : MPEG-4
Format profile                           : QuickTime
Codec ID                                 : qt   0000.02 (qt  )
File size                                : 69.4 MiB
Duration                                 : 20 s 0 ms
Overall bit rate mode                    : Variable
Overall bit rate                         : 29.1 Mb/s
Frame rate                               : 30.000 FPS
Writing application                      : Lavf58.29.100

Video
ID                                       : 1
Format                                   : ProRes
Format version                           : Version 0
Format profile                           : 4444
Codec ID                                 : ap4h
Duration                                 : 20 s 0 ms
Bit rate mode                            : Variable
Bit rate                                 : 29.1 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 30.000 FPS
Chroma subsampling                       : 4:4:4
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.467
Stream size                              : 69.4 MiB (100%)
Writing library                          : fmpg

[rodlie]

Anyway, could you give me an example on how to correctly use the "advanced options? Anything I try looks like has no effect:

This is not regular commandline arguments, see type. You can only add meta, format and codec args.

[pgilfernandez]

This is not regular commandline arguments, see type. You can only add meta, format and codec args.

so no way to force constant FPS here, right?

[rodlie]

Kind of...

https://trac.ffmpeg.org/wiki/Encode/H.264

You will need to experiment a bit, but setting a fixed gop may work better with kdenlive.

In advanced options do:

Type	Key	Value
Codec	x264-params	keyint=30:min-keyint=30:scenecut=0:force-cfr=1

Replace 30 with whatever FPS you use. This is an example, you may need to adjust.

[rodlie]

Ok, so I looked through the code and tested exported videos in various media apps/validators and the video is CFR. This is also the default for MP4 and required for ProRes.

IMHO kdenlive is wrong until someone can provide info that says something else.

[pgilfernandez]

Ok, so I looked through the code and tested exported videos in various media apps/validators and the video is CFR. This is also the default for MP4 and required for ProRes.

But then, why HandBrake makes a valid one? There must be a small difference that kdenlive passes it... Now I don't remember where but I've seen that the Feiction videos were 60,22fps and not exactly 60, could it be related with this?

IMHO kdenlive is wrong until someone can provide info that says something else.

Yes, we need to spot the difference so that we can try to add it...

Meanwhile, I tried the advanced options you suggested and some more I did but didn't find the solution. Even asking ChatGPT... the fact is that it says that the video is encoded before adding these parameters so if the problem is already present at encoding, it is hard to hide it "with some make up".

In the meantime I tried kdenlive 24.02 and you were right, it is not picky as newer versions... I don't like the UI as 24.12.0 is much polished and more beautiful but it's a way to shorten the workflow and don't have in between encodings...

[pgilfernandez]

I've been doing some more tests and they are pointing me now that the problem may be related with the saved framerate, that even being constant FPS it is not exactly 60 but 60,20.

This is the FFMPEG information with a video rendered with Friction (and kdenlive says it needs to betranscoded):

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'lookAt_friction.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.29.100
  Duration: 00:00:05.00, start: 0.000000, bitrate: 5637 kb/s
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080, 5630 kb/s, 60.20 fps, 60 tbr, 15360 tbn, 120 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]

This is the same video but converted with HandBrake (and kdenlive likes it):

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'lookAt_friction_handbrake.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 512
    compatible_brands: mp42iso2avc1mp41
    creation_time   : 2025-03-29T11:30:37.000000Z
    encoder         : HandBrake 1.6.1 2023012200
  Duration: 00:00:05.00, start: 0.000000, bitrate: 5841 kb/s
  Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 5833 kb/s, 60 fps, 60 tbr, 90k tbn, 120 tbc (default)
    Metadata:
      creation_time   : 2025-03-29T11:30:37.000000Z
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]

Another test I did was with a Quicktime screen capture which has variable FPS (and it's expected that kdenlive is not going to like):

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/Users/pablo/Desktop/friction_trim_path_quicktime.mov':
  Metadata:
    major_brand     : qt  
    minor_version   : 0
    compatible_brands: qt  
    creation_time   : 2025-03-19T11:59:43.000000Z
    com.apple.quicktime.make: Apple
    com.apple.quicktime.model: MacBookPro13,3
    com.apple.quicktime.software: macOS 12.7.6 (21H1320)
    com.apple.quicktime.creationdate: 2025-03-19T12:59:07+0100
  Duration: 00:00:09.01, start: 0.000000, bitrate: 4065 kb/s
  Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 2560x1440 [SAR 1:1 DAR 16:9], 3840 kb/s, 58.42 fps, 60 tbr, 6k tbn, 12k tbc (default)
    Metadata:
      creation_time   : 2025-03-19T11:59:43.000000Z
      handler_name    : Core Media Video
      vendor_id       : [0][0][0][0]
      encoder         : H.264

And here is the video converted with HandBrake (that kdenlive likes it as expected):

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/Users/pablo/Desktop/friction_trim_path_quicktime_handbrake.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 512
    compatible_brands: mp42iso2avc1mp41
    creation_time   : 2025-03-20T21:30:19.000000Z
    encoder         : HandBrake 1.6.1 2023012200
  Duration: 00:00:09.00, start: 0.000000, bitrate: 331 kb/s
  Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 2560x1440 [SAR 1:1 DAR 16:9], 325 kb/s, 60 fps, 60 tbr, 90k tbn, 120 tbc (default)
    Metadata:
      creation_time   : 2025-03-20T21:30:19.000000Z
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]

What do you think? could it be related with that "non exactly" FPS number?

[pgilfernandez]

I think that's the problem!

I tried just remuxing the video (a Friction rendered video), that is, no reencoding, just changing the container and header.

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/Users/pablo/Desktop/lookAt_friction_remuxed.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.76.100
  Duration: 00:00:05.02, start: 0.000000, bitrate: 5618 kb/s
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080, 5612 kb/s, 60 fps, 60 tbr, 15360 tbn, 120 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]

And what is more important, kdenlive likes it!, it doesn't need to transcode it.

What do you think? could it be something easy to solve at Friction code level? I could have a look at Friction code but you are more experienced and you said you already checked it the other day...

[pgilfernandez]

I added a fix to videoencoder.ccp that seems to work.
I'm going to do some more tests before PR it later today
☺️

[pgilfernandez]

Well, I proposed a PR https://github.com/orgs/friction2d/discussions/491#discussioncomment-12640696 that may fix the problem.
Let's continue discussing it there.