Problem saving using 'copy'

[DRWin]

I'm trying to combine two AVCHD video clips by appending one to the other.
However, when I try to save I get this message:
"This video uses non-IDR recovery points instead of IDR as keyframes..."  And a warning that "the choice of cut points may result in playback interruption..."
I've tried combining the two clips without changing them.
I've tried ensuring that the first and last frame of each clip is an I-frame.
I can save them, but they can't be played on any player I can find.
What is the solution to this problem?
Thanks in advance!

[eumagga0x2a]

First of all, please check that the issue persists with the latest 64-bit 2.7.7 nightly from https://avidemux.org/nightly/win64/

If the nightly confirms that the cut point between the two streams is not viable, you could experiment with deleting a few GOPs across the boundary. However, the only reliable way to handle open GOP type streams is to re-encode.

[DRWin]

Thanks, I'll try that.
Meanwhile, what is 'GOP' in this context?  Is 'boundary' the boundary between the two clips?
Thanks,
DR

[DRWin]

I installed the latest nightly as you suggested, and that seems to have solved the problem.
Thank you!

[eumagga0x2a]

Might have been a false positive from bugs present in the release but fixed thereafter.

Regarding your question: GOP = group of pictures = all frames in stream order starting with a keyframe until the next one.

With closed GOPs, these keyframes are always IDR (instantaneous decoder refresh) frames which means no references from frames preceding the keyframe are allowed (each GOP is self-contained). With open GOPs, keyframes are merely direct access frames for seeking, with all the internal structure of the stream continuing. References may (well, they simply almost always do) cross GOP boundaries making clean cuts impossible.

The problem with POC going back is a complication at a different level, it is FFmpeg not resetting MCO (memory control operations) on POC discontinuities, leading to grave issues like picture freezing for a long time and severely damaged pictures. Even with POC not diminishing across a cut, artifacts from missing references are possible and likely.

Is 'boundary' the boundary between the two clips?

Yes, exactly.