Framerate conversion with avisynth - help needed

[ThomasM]

Hi there,

again, I try to do some conversion with AVIsynth. I think I got it right now, because in the attached workflow some configurations work, others do not. I will explain.

PROBLEM:
- Film scanned at 18 FPS, ProRes 422 HQ .MOV format 1080p 4:3 1440x1080
- Original speed is 16 FPS
- Output format must be 25 FPS

I Tried th attached Workflow. It goes like this:

- PickUp-Folder (Or, submit manually...)
- A/V-Media Node (for following AVIsynth-nodes)
- Custom AVIsynth (Assume 16fps = Set source to 16 FPS ----- RIGHT OR NOT? -----)
- FPS-Converter Node set to 25 FPS with blending.
- ENCODER-NODES (Here is where it all happens to go wrong...)
- DV / DVCpro: Works as expected, the original 4 second Clip is now 9 seconds long and is slower with blended frames. But it is SD...
- Custom FFMPEG Node LibX264 gives Error "No video or Audio Found in Media (!)
- DEFAULT CustomFFMPEG-Node ended with the same error - no AV...
- AVC-Intra Does only encode 6 seconds out of nine



I hope I did all the things right with this DropBox thing: I Uploaded a short .mov. This is actually NOT 16 FPS, but this is a Scan at 18 FPS. With this Clip I tried th attached Workflow (Workflow also on DropBox).

https://www.dropbox.com/sh/7uxzziteeb9o ... Fg8Ha?dl=0

Any ideas?

thx,

tom

[admin]

Hi tom,

Why the AVC-Intra encoder creates shorter output is a bit strange so I will have to take a look at that. That "said", there is a couple of wierd stuff with your file and workflow. First, the original file has a framerate of 25, and by the looks of the people moving, the current playback rate seems fine. But you want the playback rate to be slower (16 fps)? If so, the "AssumeFPS(16)" is correct but checking the "Keep source playback frame rate" is wrong. It will make the clip play even slower than 16 fps.

If you want to use the "Custom FFmpeg" encoder node you need to limit the amount of channels to f.ex. two by adding the "Channel Mapper" filter. This is described directly in the "Custom FFmpeg" node.

The "H.264"-encoder node has a bug when selecting display aspect other than "Auto" and "Same as source". That's why it fail. Set it to "Auto". The bug has been fixed for the next release coming soon.

-steinar

[ThomasM]

Hi Steinar,

thank you very much for your fast response.

Let me clear up the part with the framerate:

The Clip provided is only an example. It is 24fps. It is scanned frame-by-frame to an .AVI-File. The .AVI-File has a framerate-Signature of 25 fps no matter what the input. In other words, the scanner does not know what speed the film is. It sees only frame 1, frame 2, (...) frame n. So 25 frames give, this would be the one-second-video. But, if the film was made with 16 (or 18 or 20...) fps, the speed is wrong. But we keep this .AVI in the deep archive for later transcoding.

For PostPro-purposes we do a direct transcoding (sure - ffastrans... ) to ProRes 422HQ. The File on DropBox is such an example. I did only a four-second-clip, so I can see what the transcoding is doing. The original clips are about 25 Minutes...

From this ProRes-MOV we do another transcoding in h264 (sure - ffastrans... ). Just for research-purposes, so that the files are handy.

BUT... the guys who give us the film-material want to have it on their desktop. or via USB on their flat and so on. So we decided to give them slowed down versions. But there is a problem. When just assuming 16fps with the avisynth, the outcoming file is only played back correctly in VLC. When trying to do a home DVD, the software strikes (I don´t know exactly how they tried it, but they had success with pure 25fps-films). So we had the idea of doing this workflow Film -> frame-by-frame Mov @25 -> Assume 16 -> change FPS to 25 -> Output File to be happy...

The whole workflow is much more complex as I added conditional nodes for checking what fps is to be assumed.

But... thank you for the Bug-message. I will give the h264-node a try tomorrow. I also had the channelmapper-node in, but I tried it with and without it. Maybe there is something else bad in my script...

Again - thanks,

Thomas

[ThomasM]

Ok, i tested everything. Now it works on one of my computers. But the quality of the blending option of the change fps node is bad so wedecided for not blending.

But we are so happy, that this workflow is running now! Thank you, Steinar!

all the best,

Thomas