Alpha channels Offset by 1 frame

We have a problem with alpha channels being offset by 1 frame coming out of Action.

We have a series of single frame cartoon effects, png each with alpha channel. These are being merged to create a sequence.
First thing i am doing is using a Mux to freeze frame the foreground and alpha channel of each clip, then using a separate multi input Mux to switch between each frame.

When we render out from Action, the resulting video has the alpha channel switching 1 frame early. I have not added any offsets - and we have tried this on two different Flames - 2023 and 2024 - each on a different Mac.

Anyone else seen this ?

This sounds strange. Is your mux to create a sequence using expressions? And is the action outout one output with both, fill& alpha, or are they 2 different outputs?

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no expressions used, input and output all use fill and alpha. Going through the Action frame by Frame everything lines up correctly. When i render it out i get the 1 frame alpha offset.

whats really weird is we have created 6 different graphic sequences, all created exactly the same way in Illustrator and Photoshop, but its only this one set of frames that is having problems…all the others work perfectly.

have also tried rendering as both Multi channel and RGB-A - and the problem persists.

Do you

accidentally have a slip in the Action node?

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Thanks Bryan, I’ll check tomorrow, but i doubt that would be happening on two completely unconnected Flames, when the shot has been created from scratch both times.

Not had this problem before @Lightningad but you could try a different approach. Maybe stitch the alpha files together in a different way? You can splice a reel of single frames to make a clip. This might have less problems :thinking:

Good idea…will try in the morning…thanks richard

just checked - no slip on any inputs.

I have just taken a fresh look at the issue and realised that what is actually happening is not the alpha slipping by a frame but the first frame of the next shot, the `fill is being squashed on the first frame, then correct on the subsequent frames.

More experimenting and it seems to be fixed. Re- exported from Photoshop, brought in as individual PNG files, not used a Mux to freeze each but did use resize node on each with crop options set to Destination and Letterbox…suddenly it just works! No clue why this set of images took so much when the other 5 worked first time!

thanks for all the suggestions, chaps!