Feature Request: Transparent Video Export

I realize this may not be useful for everyone, but I’ve been using FWSim to create video overlay assets for live streaming and other video projects. To accomplish this one must use a color keyer filter/effect and reprocess the video file exported by FWSim. Which - as you can imagine, is not ideal as it drastically reduces the quality of the FW effects on the stream.

Is there any possibility that an alpha channel could be added to the MP4 video export? MP4 (ProRes4444) and (WebM) both have native alpha channel support, and would be a brilliant addition to the simulator’s output options.

This would catastrophically improve the quality and usefulness of the exported videos. Not just for streaming, but also for adding fireworks to images and videos.

Alternatively… an OBS plugin/player which is capable of rendering a saved show directly in OBS would be even better. But perhaps one thing at a time. hehe


good to hear FWsim is useful for your video projects.

Currently, videos exported from FWsim do not have an alpha channel. However, when you export a video from FWsim with a black background, it is possible to simply use the brightness of the pixels as alpha. No alpha channel is needed.

You mention you are using OBS for streaming. Which other video editing programs are you using?
If you let me know which programs you are using, I might be able to post some more detailed instructions on how to get FWsim videos in there.

Best Regards,

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I use final cut pro to key/remove the black and prepare for OBS. Which works - but it’s never perfect and almost always reduces the quality of the fireworks. Which is why I thought I’d request an alpha channel be added to exported MP4s.
Ideally it would be rather nice to have a WebM export which includes an alpha channel and no background, but I realize this entire ‘request’ is likely outside the scope of what you’re creating with the sim. So I completely understand if it’s not something worth putting the effort into.

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Thanks for the explanation. I understand you’re using OBS Studio (Open Broadcaster Software) to layer FWsim on top of other video sources. And you are using Final Cut Pro to remove the black from FWsim videos.

You actually don’t need to use Final Cut Pro, and you don’t need an alpha channel. When you export videos with just fireworks and no background, and you use the right alpha blending mode in OBS, everything looks great without needing to pre-process the video file.

Please try this:

  1. Make sure you have the latest version of OBS
  2. Load your desired background into OBS. (Could be an image, or any other video source)
  3. Load the FWsim video as a media source into OBS
  4. Right-click the FWsim video, select “Blending Mode → Additive”.
  5. It will look like this:

If you get a chance to try this, please let me know how it works for you.

(Image Credits: Alexey Elfimov)


Thanks for the reply… and sorry for the delayed response. YES, hehe, Additive makes it much easier to deal with. THanks for that.

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