When doing character animation, I typically use Toonboom Harmony, and then render out PNG4 sequences for compositing in AE. However, since version 15.0.1, I've been having an issue where my PNG sequences were not having their alpha interpreted. While this is hard to convey without pictures, here's how I solved the issue and it may help you guys to squash the bug:

1) In Toonboom, I create an animation that starts on a full background, no alpha channel, then transitions in-animation to a wipe that then needs to be comped in AE.

2) Render it out as a PNG4 sequence with no color card, alpha enabled.

3) Before this update, AE would see the PNG4 and interpret the alpha channel at the end of the sequence, allowing for easy comping. However, in 15.0.1, no dice.

4) I bring one of the PNGs in Photoshop to double check if the PNG has alpha and, sure enough, it does.

5) I look at the sequence in AE for a minute and then have the idea that because the FIRST frame of this sequence does NOT have alpha, AE believes the WHOLE sequence does not have alpha, and thus does not interpret the PNGs that DO have an alpha channel.

6) I go back to Toonboom and render out the same PNG4 sequence but this time with one additional frame in the beginning: an empty frame, nothing in it. Pure alpha.

7) I bring the new sequence into AE and voila! The alpha channel for the whole sequence is now able to be interpreted, allowing for easy comping.

Of note, I tested this with an Animation codec render .mov, as well. When rendered at Millions of Colors+, if the starting frame has no alpha, the whole video is interpreted as having no alpha. Add one empty frame of pure alpha, and AE interprets the alpha and you can comp it.

This isn't just AE- the problem also exists in Premiere, where I do most of my editing.

It's an issue that I can work around, as adding one empty frame of alpha requires little on my end, but I can imagine that this will prove to be a headache for a lot of people that can't seem to get it to work, especially when it did until very recently.

Thanks for reading and listening! I look forward to a change.