This IS the Avid L2: [Avid-L2] AMA Clip duration issue

Here's an issue with ProRes AMA files that I haven't seen discussed before... Has anyone encountered AMA linked clips having a different duration than the source file?

I have an entire doc that was shot on ProResHQ. (1920/23.98 project on both an MC6.5 and Symphony 6.) We AMA-linked the camera files and transcoded to DNx36. For finishing, we knew that AMA ProRes clips have incorrect video levels (which Source Settings adjustments do not fix), so we did a 709 Fast Import of the camera files (which maintain proper levels). The edited sequence re-linked to the Imported ProRes Avid media without an issue.

However, we found that the full DNx36 clips would not relink to the same ProRes Avid media, and discovered that the AMA clips are 1 or 2 frames longer duration than the 709 Fast Imports! The AMA clips show an extra frame or two at the tail that is a duplicate of the very first frame of the clip. This occurs in 1000s of files that were AMA/Transcoded over the past year on MC6.5.

I did some more testing on these and with other camera files and got varying – and maddening! – results:
* Sometimes, the AMA clips are 1 frame shorter than the 709 Fast Imports – the last frame is missing.
* I've also seen the same camera file AMA-link with extra frames at the end, and then, at another time, AMA-link with no extra frames.
* A standard RGB Import of the same file (neither fast, nor accurate for video level) adds an extra frame at the end.
* DNx imports of the ProRes files also seem to add an extra frame… most of the time.

I suspected that the camera files were corrupt in some manner – they all come from an Atomos Samurai. However, opening the same files in FCP7 does not present any such issues. And, I believe the 709 Fast Imports of the ProRes camera files are perfect – have not found any extra or missing frames in any of them.

This duration mis-match leads to all sorts of workflow issues with relinking, batch importing, etc. that I've been trying to work out. More about that at another time! When I get a handle on it, I'll provide more details that might be of interest to the list.

Thanks in advance for an feedback or insights!
Craig Mikhitarian
ACM Productions, Ltd.