Combining videos corrupts appended videos

[Avidummy]

When combining two mp4s on copy mode, the second mp4 is garbled.  The codec settings should be precisely the same, and if they are not I'd like to know why.

Version 2.8.2

I'm joining 20-second trailcam AVIs by encoding with h264.  That part works fine.

I drag first AVI into window, then next AVI, etc.  Then 2-pass encode with h264.  Result is video1.

Then go to file, close, and then start dragging more AVIs to join and encode.  Result is video2.  All is well.

Then I change video and audio output to copy and attempt to join video1 and video2.  The result is video2 is corrupted when appended to video1.  How is that possible if both mp4s were encoded by the same session of avidemux without making any changes?


Size:            47
Extradata:         01 64 00 28 FF E1 00 1B 67 64 00 28 AC D9 40 78 02 27 E5 C0 44 00 00 03 00 04 00 00 03 00 CA 3C 60 C6 58 01 00 05 68 EB E5 2C 8B FD F8 F8 00

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Size:            48
Extradata:         01 64 00 28 FF E1 00 1B 67 64 00 28 AC D9 40 78 02 27 E5 C0 44 00 00 03 00 04 00 00 03 00 CA 3C 60 C6 58 01 00 06 68 EB E3 4B 22 C0 FD F8 F8 00

When using 2.8.1 I noticed the frame rate was changed to fractional for no reason.  2.8.2 fixed that.  Now it appears codec settings are changing for no reason?  Is that a known issue?

Now that the damage is done, how can I join those videos without increasing the size or decreasing the quality?