Is this a drive failing?

[mwebb]

If MakeMKV tells you there is no error, then why are you checking again with ffmpeg? I would trust MakeMKV over ffmpeg's error check.

Becuase I see repeatable glitches in playback of the MKV, even though MakeMKV had no errors. VLC can play the disc without glitching, however glitches when it replays the MKV. I'm assuming there is therefore something "up" with the MKV which ffmpeg would tend to confirm I believe?

[mwebb]

Then load the .m2ts and let it analyze. Switch the output view to seconds and compare the timestamp with the highest bitrate(s) with the timestamp where your distortions appear.

I haven't gotten this far in testing yet, howver the NUC seesm to be both reading from and writing to the internal HDD at north of 100 megabytes/s and disc appears to maxing out at around 100 megabits/s all in. That would seem to be quite a sizeable bandwidth margin?

[mwebb]

If you used MakeMKV to read the UHD disc, then a non-error completion (meaning file hashes of read data were checked) indicates that reading was successful.

However, if you have a flakey setup for writing the copied data, then what was actually saved could have errors, even if the data that the system was attempting to write was itself correct. That could affect not just optical disc copying, but any data written to the drive, and could also result in the filesystem getting corrupted.

Typical causes of this are bad data or power cables, or an underpowered USB connection (like a computer's or hub's USB port with limited USB power output). So a connected external SSD or portable hard drive may have just enough power to be seen by the host computer and occasionally write some data successfully, but will write bad data from time to time, or go offline suddenly without completing a deferred write, etc. For example, I know that with a powered USB hub that I use, when I connect an external SSD or portable hard drive to it with the hub's power supply active, things work well. If I do not connect the hub's power supply, the USB bus supplies enough power to make the storage device visible an able to write some data, sometimes incorrectly, and occasionally go offline suddenly -- meaning enough power to cause trouble.

As I'm using a tall NUC I'm writing to an internal SATA HDD, with the source being a powered external optical drive enclosure attached directly to a NUC USB port. CHKDSK reports the drive as clean. If MakeMKV finishes without error, then at the very least the disc, the optical drive, the enclosure and the connection to the computer can't be at fault? Is that the concensus?

[kaysee]

Your hard drive may be getting bogged down during playback, which is why it would be worthwhile to check whether frames are getting dropped. You still have not indicated what OS you are using. On Windows, you can use the Resource Monitor to observe active time for a disk. If that approaches 100% during playback of a video, then you have a problem. Under Linux, you can use iotop.

[mwebb]

Apologies; Windows 11.