I'm having strange issue with Blender 2.9 and above (so 3.0 too), which is not happening for earlier versions. Video Sequence Editor has trouble working with .mp4 encoded using PNG video codec, containing an alpha channel. It's rendered in Blender 2.81. VSE either imports it with correct number of frames but without alpha channel or just as a 1 frame with an alpha channel. Compositor in the same versions of Blender don't have this issue. Imports and interprets the alpha channel correctly. I'm working on Ubuntu 20.04.3 LTS GeForce GTX 1050 Ti and NVIDIA Driver Version:390.144. Installed Python versions: 2.7.18 and 3.8.10 Anything that comes to your mind will be helpful cause I have no clue where to start looking.

  • $\begingroup$ Did you change the blending mode from Cross to Alpha Over? $\endgroup$ Dec 8 '21 at 11:01
  • $\begingroup$ Of course @joshsanfelici and if I wouldn't it still didn't explain importing just one frame instead of whole video in some cases. $\endgroup$
    – Mzidare
    Dec 8 '21 at 12:01
  • $\begingroup$ mp4 does not support alpha. $\endgroup$ Dec 8 '21 at 16:03
  • $\begingroup$ @MartyFouts So how is that I can use .mp4 videos with alpha channel properly in earlier Blender versions and Open Shot both on Linux and Windows 10 and Blender 2.9+ reads it properly in Compositor? $\endgroup$
    – Mzidare
    Dec 8 '21 at 16:06
  • $\begingroup$ list of formats that support alpha You can import an mp4 and do a substitution to derive an alpha channel from a background color, but you have to output in a format that does support alpha. $\endgroup$ Dec 8 '21 at 16:11

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