Alpha channel is transmitted from Adobe Premiere Pro 2026, but not from After Effects 2026.

[ariestav]

macOS Tahoe 26.2 / After Effects 2026
When the active composition viewer has transparency (checkered bg), those pixels are actually sent via Mercury Transmit without any alpha information, making compositing on a play out app like OBS very limited. The color set within the composition's setting dialog is what is passed onto the transmitter.

macOS Tahoe 26.2 / Premiere Pro 2026
When the active timeline viewer has transparency those pixels are sent as transparent pixels to Mercury Transmit within Premiere Pro. This seems like how it should be so that graphics can be super imposed onto a composite in a play out app like OBS.

So in the After Effects context transparency does not seem to transmit, but in Premiere Pro the transparency does seem to work a-okay.

I dug into Syphon's source and it does seem like the alpha channel data is considered when handing off to the host app (AE or PPro), but the problem persists.

My guess is that this is a host-app issue, but wanted to post here in case anybody ran into this issue with transparency in After Effects. Any insight into the various hosts that do or don't support transparency?

[vade]

Hey excited folks are actually using this haha :D

My suspicion is that AE maybe does premultiplied alpha vs un-premultiplied or maybe vice versa?

I know a person on the AE Team, i can ask! Maybe i can sneak a license too haha.

[ariestav]

Happy to test it — I'd like to incorporate it into a larger product, but because AE does not send Alpha information, it's very limited. I wondered if it's specifically an AE thing or something else. Also, there is a "bug" for this on the Adobe Community Forums.