After Effects 15.1 broken AVI support?

I have received clarification from our developers that on macOS, AVI files can no longer be imported into After Effects 15.1, Premiere Pro 12.1, or Adobe Media Encoder 12.1. This does not affect Windows; AVI files can continue to be imported there, as Windows provides the service to parse and decode the files.

As I described above, the reason for the change on macOS was the removal of legacy 32-bit QuickTime processes. On macOS, the only AVI parsing and decoding service available was in 32-bit QuickTime; the applications do not contain this capability natively.

donbarrum  wrote Why not remove the ability to render these codecs instead of removing the ability to open files of old quicktime codecs entirely?

That is not possible.

Support for both decoding and encoding legacy 32-bit QuickTime codecs is dependent on the 32-bit QuickTime processes. As Apple is dropping support for 32-bit QuickTime processes altogether, it's not possible to have one without the other.

And, even ProRes cant be opened now... which is such a vastly used codec, still. This will create a huge problem for everyone not being able to even open them.

Adobe applications continue to support ProRes codecs. Per this page ( Dropped support for Quicktime 7 era formats and codecs ), After Effects, as well as Premiere Pro and Adobe Media Encoder, can import and export ProRes on macOS, and import ProRes on Windows. (These applications have never had a native ProRes encoder on Windows. That wasn't possible even with the legacy 32-bit QuickTime processes; Apple did not allow that.)

That said, we are investigating reports that some ProRes files can't be imported into After Effects 15.1 or Premiere Pro 12.1. On my computers, I am able to import many ProRes files, but a different file provided to me by a customer indeed fails to import.

As we are still investigating the problem, it could be helpful to have more samples of ProRes files that fail to import. Would you be willing to send us one? If so, please email a link to aebugs@adobe.com.

People, like myself have huge libraries of video files, do you find it user friendly having to convert 1000's of old videofiles to be able to continue using After Effects?

We understand that this change will be difficult for some people. Many video formats (both physical and software) have come and go over the years; this is certainly one of the more significant changes I've seen in my career. Ultimately, Adobe does not own nor control the QuickTime codecs, and we are trying to help our customers with the transition. We were aware in advance that Apple was planning to discontinue the legacy 32-bit QuickTime codecs and have done a lot of work in the past 2 years preparing for this by adding native support to our applications for the most common codecs (based on application usage data and talking with customers).

As I said above, if there is another codec you would like us to support natively, please submit a feature request. (It is unlikely that we will add support for all of the legacy 32-bit QuickTime codecs, but if certain codecs are popularly requested we will consider what work it would take to support them.) And you can also transcode your files with older versions of Adobe applications, or another application of your choice.