The Professional AV Sync Issues

[corruption]

I know everyone who posts about AV Sync Issues seems to be directed to this thread
viewtopic.php?t=21079 but I don't see a definitive answer there--am I missing it?

Is it really dropping frames to maintain sync? Thanks!

Leon, The Professional UHD Canadian disc UPC 0 43396 51209 2

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MakeMKV v1.15.2 win(x64-release) started
Debug logging enabled, log will be saved as [redacted]
Opening files on harddrive at [redacted]
Loaded content hash table, will verify integrity of M2TS files.
File 00102.mpls was added as title #0
File 00505.mpls was added as title #1
File 00506.mpls was added as title #2
File 00520.mpls(4) was added as title #3
File 00521.mpls(4) was added as title #4
File 00522.mpls(1) was added as title #5
File 00522.mpls(2) was added as title #6
File 00523.mpls(4) was added as title #7
Title #00001.m2ts has length of 112 seconds which is less than minimum title length of 120 seconds and was therefore skipped
Title #00080.m2ts has length of 6 seconds which is less than minimum title length of 120 seconds and was therefore skipped
Title #00081.m2ts has length of 17 seconds which is less than minimum title length of 120 seconds and was therefore skipped
Title #00082.m2ts has length of 10 seconds which is less than minimum title length of 120 seconds and was therefore skipped
Title #00100.m2ts has length of 14 seconds which is less than minimum title length of 120 seconds and was therefore skipped
Title #00104.m2ts has length of 0 seconds which is less than minimum title length of 120 seconds and was therefore skipped
Title #00116.m2ts has length of 11 seconds which is less than minimum title length of 120 seconds and was therefore skipped
Title #00208.m2ts has length of 10 seconds which is less than minimum title length of 120 seconds and was therefore skipped
Title #00335.m2ts has length of 60 seconds which is less than minimum title length of 120 seconds and was therefore skipped
Title #00336.m2ts has length of 112 seconds which is less than minimum title length of 120 seconds and was therefore skipped
Title #00337.m2ts has length of 39 seconds which is less than minimum title length of 120 seconds and was therefore skipped
File 00338.m2ts was added as title #8
Title #00339.m2ts has length of 60 seconds which is less than minimum title length of 120 seconds and was therefore skipped
File 00340.m2ts was added as title #9
File 00341.m2ts was added as title #10
File 00342.m2ts was added as title #11
File 00343.m2ts was added as title #12
File 00347.m2ts was added as title #13
Title #00349.m2ts has length of 6 seconds which is less than minimum title length of 120 seconds and was therefore skipped
Title #00350.m2ts has length of 17 seconds which is less than minimum title length of 120 seconds and was therefore skipped
File 00351.m2ts was added as title #14
File 00354.m2ts was added as title #15
Title #00355.m2ts has length of 29 seconds which is less than minimum title length of 120 seconds and was therefore skipped
File 00356.m2ts was added as title #16
Operation successfully completed
Saving 2 titles into directory [redacted]
AV synchronization issues were found in file '[redacted]Professional, The (1994)_t01.mkv' (title #2)
AV sync issue in stream 2,3,4 at 0:01:52.737 with duration of 30.375ms : encountered overlapping frame, audio skew is +30.375ms
AV sync issue in stream 1 at 0:01:52.736 with duration of 0.83ms : encountered overlapping frame, audio skew is +1.33ms
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
AV sync issue in stream 2,3,4 at 0:45:42.698 with duration of 23.333ms : encountered overlapping frame, audio skew is +53.708ms
AV sync issue in stream 2,3,4 at 0:45:42.752 with duration of 32ms : 1 frame(s) dropped to reduce audio skew to +21.708ms
AV sync issue in stream 1 at 0:45:42.697 with duration of 0.833ms : encountered overlapping frame, audio skew is +2.163ms
AV sync issue in stream 1 at 0:45:42.699 with duration of 1.666ms : 2 frame(s) dropped to reduce audio skew to +0.497ms
AV sync issue in stream 2,3,4 at 0:46:22.196 with duration of 22.208ms : encountered overlapping frame, audio skew is +43.916ms
AV sync issue in stream 2,3,4 at 0:46:22.240 with duration of 32ms : 1 frame(s) dropped to reduce audio skew to +11.916ms
AV sync issue in stream 1 at 0:46:22.194 with duration of 0.83ms : encountered overlapping frame, audio skew is +1.327ms
AV sync issue in stream 2,3,4 at 1:08:17.510 with duration of 14ms : encountered overlapping frame, audio skew is +25.916ms
AV sync issue in stream 1 at 1:08:17.508 with duration of 0.833ms : encountered overlapping frame, audio skew is +2.161ms
AV sync issue in stream 1 at 1:08:17.510 with duration of 1.666ms : 2 frame(s) dropped to reduce audio skew to +0.494ms
AV sync issue in stream 2,3,4 at 1:11:20.276 with duration of 18.083ms : encountered overlapping frame, audio skew is +44ms
AV sync issue in stream 2,3,4 at 1:11:20.320 with duration of 32ms : 1 frame(s) dropped to reduce audio skew to +12ms
AV sync issue in stream 1 at 1:11:20.274 with duration of 0.838ms : encountered overlapping frame, audio skew is +1.333ms
AV sync issue in stream 1 at 1:11:20.275 with duration of 0.833ms : 1 frame(s) dropped to reduce audio skew to +0.5ms
AV sync issue in stream 2,3,4 at 1:20:42.754 with duration of 17.416ms : encountered overlapping frame, audio skew is +29.416ms
AV sync issue in stream 1 at 1:20:42.753 with duration of 0.827ms : encountered overlapping frame, audio skew is +1.327ms
AV sync issue in stream 2,3,4 at 1:21:12.534 with duration of 12.25ms : encountered overlapping frame, audio skew is +41.666ms
AV sync issue in stream 2,3,4 at 1:21:12.576 with duration of 32ms : 1 frame(s) dropped to reduce audio skew to +9.666ms
AV sync issue in stream 1 at 1:21:12.532 with duration of 0.838ms : encountered overlapping frame, audio skew is +2.166ms
AV sync issue in stream 1 at 1:21:12.535 with duration of 1.666ms : 2 frame(s) dropped to reduce audio skew to +0.5ms
AV sync issue in stream 2,3,4 at 1:44:00.234 with duration of 12.333ms : encountered overlapping frame, audio skew is +22ms
AV sync issue in stream 1 at 1:44:00.232 with duration of 0.833ms : encountered overlapping frame, audio skew is +1.333ms
AV sync issue in stream 1 at 1:44:00.234 with duration of 0.833ms : 1 frame(s) dropped to reduce audio skew to +0.5ms
AV synchronization issues were found in file 'Professional, The (1994)_t01.mkv' (title #2)
Forced subtitles track #6 turned out to be empty and was removed from output file
Forced subtitles track #8 turned out to be empty and was removed from output file
Forced subtitles track #12 turned out to be empty and was removed from output file
Forced subtitles track #14 turned out to be empty and was removed from output file
AV synchronization issues were found in file '[redacted]Professional, The (1994)_t02.mkv' (title #3)
AV sync issue in stream 2,3,4 at 0:01:52.695 with duration of 8.083ms : encountered overlapping frame, audio skew is +8.083ms
AV sync issue in stream 1 at 0:01:52.694 with duration of 0.827ms : encountered overlapping frame, audio skew is +1.327ms
AV sync issue in stream 2,3,4 at 0:45:42.656 with duration of 23.333ms : encountered overlapping frame, audio skew is +31.416ms
AV sync issue in stream 1 at 0:45:42.655 with duration of 0.833ms : encountered overlapping frame, audio skew is +2.161ms
AV sync issue in stream 1 at 0:45:42.657 with duration of 1.666ms : 2 frame(s) dropped to reduce audio skew to +0.494ms
AV sync issue in stream 2,3,4 at 0:46:43.175 with duration of 25.208ms : encountered overlapping frame, audio skew is +56.625ms
AV sync issue in stream 2,3,4 at 0:46:43.232 with duration of 32ms : 1 frame(s) dropped to reduce audio skew to +24.625ms
AV sync issue in stream 1 at 0:46:43.174 with duration of 0.83ms : encountered overlapping frame, audio skew is +1.325ms
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
Program reads data faster than it can write to disk, consider upgrading your hard drive if you see many of these messages.
AV sync issue in stream 2,3,4 at 1:08:38.489 with duration of 14ms : encountered overlapping frame, audio skew is +38.625ms
AV sync issue in stream 2,3,4 at 1:08:38.528 with duration of 32ms : 1 frame(s) dropped to reduce audio skew to +6.625ms
AV sync issue in stream 1 at 1:08:38.487 with duration of 0.833ms : encountered overlapping frame, audio skew is +2.158ms
AV sync issue in stream 1 at 1:08:38.490 with duration of 1.666ms : 2 frame(s) dropped to reduce audio skew to +0.491ms
AV sync issue in stream 2,3,4 at 1:28:42.275 with duration of 22.083ms : encountered overlapping frame, audio skew is +28.708ms
AV sync issue in stream 1 at 1:28:42.273 with duration of 0.838ms : encountered overlapping frame, audio skew is +1.33ms
AV sync issue in stream 2,3,4 at 1:38:04.753 with duration of 17.416ms : encountered overlapping frame, audio skew is +46.125ms
AV sync issue in stream 2,3,4 at 1:38:04.800 with duration of 32ms : 1 frame(s) dropped to reduce audio skew to +14.125ms
AV sync issue in stream 1 at 1:38:04.752 with duration of 0.827ms : encountered overlapping frame, audio skew is +2.158ms
AV sync issue in stream 1 at 1:38:04.755 with duration of 1.666ms : 2 frame(s) dropped to reduce audio skew to +0.491ms
AV sync issue in stream 2,3,4 at 1:43:48.013 with duration of 4.416ms : encountered overlapping frame, audio skew is +18.541ms
AV sync issue in stream 1 at 1:43:48.012 with duration of 0.838ms : encountered overlapping frame, audio skew is +1.33ms
AV sync issue in stream 2,3,4 at 2:06:35.713 with duration of 12.333ms : encountered overlapping frame, audio skew is +30.875ms
AV sync issue in stream 1 at 2:06:35.712 with duration of 0.833ms : encountered overlapping frame, audio skew is +2.163ms
AV sync issue in stream 1 at 2:06:35.714 with duration of 1.666ms : 2 frame(s) dropped to reduce audio skew to +0.497ms
AV synchronization issues were found in file 'Professional, The (1994)_t02.mkv' (title #3)
Forced subtitles track #6 turned out to be empty and was removed from output file
Forced subtitles track #8 turned out to be empty and was removed from output file
Forced subtitles track #12 turned out to be empty and was removed from output file
Forced subtitles track #14 turned out to be empty and was removed from output file
2 titles saved

[dcoke22]

I only have a loose understanding of this topic, so take everything I say here with a grain of salt. Hopefully folks with more understanding that me will tell us where I'm wrong.

One has to understand a bit about how movies are assembled onto a Blu-ray or UHD. Often, a title on a disc is an assembly of multiple segments. One can think of a title as a playlist of segments. MakeMKV will tell you the name of playlist, for example:

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Source file name: 00461.mpls

and it'll tell you the list of things in the playlist:

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Segment map: 505,514,517,507,506,511,516,509,510,503,508,515,512,513,502

Each one of those segments is what we can think of as video file of a portion of the movie. A player reads the playlist and plays back the individual files in order and (hopefully) seamlessly while you watch the movie. In my example above, segment 505 is a roughly 1.25GB file that is the first 9 minutes of that movie.

Sometimes, the audio portion of a segment is ever so slightly longer than the video portion. I'm not entirely sure why, but I'd guess it is a way to make it easier for players to avoid an audio hiccup during playback. In any case, if MakeMKV is naive and just blindly concatenates the various segments together and some of those segments have audio that is ever so slightly longer than the video, by the end of the movie, the audio might be noticeably out of sync with the video. As I understand it, when the audio for a segment is 'too long' it always has a bit of the audio for the beginning of the next segment at the end of the current segment. This is essentially a tiny bit of duplicated audio.

When MakeMKV logs a message like:

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AV sync issue in stream 1 at 1:21:12.532 with duration of 0.838ms : encountered overlapping frame, audio skew is +2.166ms

The overlapping frame it is talking about is audio frames. MakeMKV is saying it found a bit of this duplicated audio. As such, the audio and video are now an imperceptible amount out of sync, 2.166ms. MakeMKV has a threshold where it decides the accumulated error is getting too far away from the video and it removes a bit of this duplicate audio to get the audio and video back in sync.

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AV sync issue in stream 1 at 1:08:17.510 with duration of 1.666ms : 2 frame(s) dropped to reduce audio skew to +0.494ms

This isn't any different than what an actual Blu-ray player is doing all the time.

The most concise explanation I've read for what's going on here is in the FAQ for a tool someone wrote to try to deal with this problem as it relates to Dolby TrueHD audio tracks. https://github.com/domyd/mlp The most recent version of MakeMKV, 1.15.2, has fixed all known problems in this area and the log messages you see are the result of that good work.


In summary, what you're seeing is normal and nothing to be concerned about.

[corruption]

I only have a loose understanding of this topic, so take everything I say here with a grain of salt. Hopefully folks with more understanding that me will tell us where I'm wrong.

What an amazing summary! Thank-you, this is much clearer now. I also appreciate the link you provided detailing exactly why this is an issue with the format. This is sticky material, IMHO.