[PD] [GEM] output gemwin to video file workaround using ffmpeg on macos

Antoine Villeret antoine.villeret at gmail.com
Fri May 29 10:23:05 CEST 2020


what about using a screen casting tool ? they are usually made for gaming
and thus optimized for real time performance.
On macos, quicktime player is a pretty simple solution for that.
The only drawback I saw is that you're stuck with the rendering window size
since the tool grab a part of the screen, you can't render at a bigger
resolution than the display's one.

My 2 cents


Le ven. 29 mai 2020 à 10:05, cyrille henry <ch at chnry.net> a écrit :

> hello,
> The open GL rendering is made in the GPU. grabbing the images by the CPU
> in order to compress them and to record them in the HDD is a slow operation.
> I think some software are able to compress the image in the GPU in order
> to grab a smaller file, but Gem don't.
> So, there is not a lot's of solution, and you already found them.
> I use pix_record when I need a correct quality of a small video. I use
> mjpa with good result.
> When I need better quality, I use pix_writer. Usually this can not be made
> in real time. I.E : I create a process that render exactly what I want,
> without human interaction. (For live performance, I record all human
> interaction in tables or texts file during the performance, then I use this
> data to play again the same performance)
> Then, It's possible to record both image annd sound in the same time. Even
> if pd will not be sync with real (external) time, the time inside pd will
> still stay consistent. I.E : even if there are lot's of audio dropout and
> the recording fps is 1/2 of the real fps, pd will still record a perfect
> audio file that will be perfectly sync with the video. You just need to
> start the audio and video recording with the same "bang".
> cheers
> Cyrille
> Le 28/05/2020 à 22:33, ffdd cchh a écrit :
> > Hi everyone,
> >
> > Is it possible to grab the OpenGL stream with ffmpeg and save to a video
> file? If so, could anyone point in the right direction as to how to capture
> the stream opened by Gem?
> >
> > The reason I ask this is that I am looking for ways to render video
> frames to a file and I have not managed a good result using neither
> [pix_record] nor [pix_writer].
> >
> > With [pix_record] I have systematically tried all codecs and colorspaces
> and I had no luck.
> >
> > With [pix_writer], I did manage high quality frames with the correct
> colorspace which I then concatenated into a video (with ffmpeg). The
> drawback I have with [pix_writer] is the time it takes to write, which
> really complicates audio and video synching.
> >
> > Thanks!!
> >
> > Fede
> > --
> > fdch.github.io <http://fdch.github.io>
> >
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