The QuickTime H.264 implementation was buggy and unsupported the entire time it was there. It should never have been there in the first place.
Apple is deprecating a lot of stuff lately, so the newest version of AE is missing several codecs that used to be available.
There is currently no way to do H.264 directly out of AE natively in the latest version. You have at least three options.
1. You can get AfterCodecs (which is a really nice thing to add to your toolkit; you get much higher quality at lower file sizes and you also get stuff like ProRes on Windows!)
2. You can render an intermediate file with a production codec (DNxHR, Cineform, etc.) out of AE’s render queue and use the Adobe Media Encoder to make your MP4 (which is what you should have been doing anyway; it lets you do multipass encoding which AE’s render queue the way you were using it never could).
3. You can send an AE comp directly to the Adobe Media Encoder.
I used to do 2 all the time. Now I do 1. I was never a fan of option 3, but some people love it. One of the advantages of just sending your AE comp to AME is that you can send it off to render and then continue working on your next project while it renders in the background.
– The Great Szalam
(The \’Great\’ stands for \’Not So Great, in fact, Extremely Humble\’)
No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.