[Cin] Fwd: New Topic

[Georgy Salnikov]

On Wed, 13 Nov 2024, Phyllis Smith via Cin wrote:

> Anyone familiar with this package? Cincity uses CinGG but obviously we all
> use other packages for specific things?
>
> *Help on slowmoVideo*
> My debian package installs perfectly and starts without issues. I can open
> the clip but on render it crashes. Using the command line I get this error:
> Have OpenCL: true useOpenCL: true true 1 1 terminate called after throwing
> an instance of 'cv::Exception' what(): OpenCV(4.6.0)
> ./modules/video/src/optflowgf.cpp:1120: error: (-215:Assertion failed)
> _flow0.size() == prev0.size() && _flow0.channels() == 2 && _flow0.depth()
> == CV_32F in fun...

I used slowmovideo for smoothing not only filmed clips, but also
artificially generated ones (such as animation of a chemical reaction
created by quantum chemical modeling software).

I never tried to kick ffmpeg directly from inside slowmo. Instead, I did
everithing stepwise under manual control:

1) Created the appropriate number of PNG snapshots

2) Loaded the PNGs into slowmoUI

3) Rendered again into PNGs

4) Inspected created PNGs (it is also possible to edit some of them, for
example, remove artifacts)

5) Run ffmpeg on the PNGs manually somehow like:

ffmpeg -f image2 -start_number 0 -i C6H6480x480.%03d.png -r 24 -vcodec libx264 t.mp4

I understand, one would wish to automate everything to get in one step. But
for testing/debugging purposes it could be handy to try it stepwise: is
slowmo unable to generate final MP4, for example, or is it unable to drive
interpolation engine, or even unable to slurp the input?

I also tested various internal ffmpeg filters for slowed motion
interpolation:

Filter 'fps' (same as the option -r 25) is fast, but the resulting video may
become shaking:
ffmpeg -i in.mov -c:v libxvid -filter:v fps=fps=25 -b:v 16000k -b:a 192k -ac 2 -ar 48000 -y out.m4v

Filter 'framerate' is also fast, the resulting video does not become
shaking, but it may become blurred:
ffmpeg -i in.mov -c:v libxvid -filter:v framerate=fps=25 -b:v 16000k -b:a 192k -ac 2 -ar 48000 -y out.m4v

Filter 'minterpolate' is free of artifacts like shaking or blur, produces
the output of much better quality, but it is slow:
ffmpeg -i in.mov -c:v libxvid -filter:v minterpolate=fps=25 -b:v 16000k -b:a 192k -ac 2 -ar 48000 -y out.m4v

_______________________________________________________________________________

Georgy Salnikov
NMR Group
Novosibirsk Institute of Organic Chemistry
Lavrentjeva, 9, 630090 Novosibirsk, Russia
Phone   +7-383-3307864
Email   sge at nmr.nioch.nsc.ru
_______________________________________________________________________________