Are AV synchronization issues a problem?

[Legenista]

I just saw Mike has released a new MAKEMKV version:

**********
MakeMKV v1.15.4 (8.12.2020 )
Improved handling for discs with mastering errors
Many internal improvements and small bugfixes
Implemented seamless joining of TrueHD streams with overlapping frames based on Dominik Mydlil's idea
MakeMKV now recognizes and converts double-track Dolby Vision MKV files
Bug fixes:
Program could fail when processing TrueHD streams from MKV file
DTS core was not extracted from DTS-HD streams (1.15.0 regression)
**********

I am going to verify if it changes anything here, and let you know the results if not today, in the next days.

What I said earlier is that if we don't know if the file has been affected, it is difficult to analyze thoroughly. MAKEMKV just saying it has A/V SYNC ISSUES and us taking hours to really make sure these are not there is not practical. I am used to rip my discs and only later go back to the files.

[Legenista]

Update: warnings are still there for Beverly Hills Cop (1984) UHD. In this case I don't know if it's a false alert, don't notice anything wrong so far.

It looks like nothing will change for BTTF part I if I try again...

[mattpr]

This is a naming issue. The 1.14.7 inserts this before printing "the subtitle track XXX turned to be empty and was removed", so you know what file this message is about. Now it is obviously confusing...

Would like to have confidence in my makemkv rips and not have surprise audio drops discovered much later that require pulling out the discs for re-ripping/naming/etc.

Attempting to sum up this issue. If we see the AV sync message...

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AV synchronization issues were found in file '______________.mkv' (title #____)

...but it is only followed by messages like...

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_____ subtitles track #___ turned out to be empty and was removed from output file

...there is no real issue and we can ignore the messages and have confidence in the rip.

We just need to keep our eyes open for actual sync errors that will have a message similar to the following...

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AV sync issue in stream X at XX:XX:XX.XXX with duration of X.XXXms : ...

...which indicates a real problem with the rip (potential audio or video drops).

Is this an accurate summary? Thanks!

[dcoke22]

I believe that is an accurate summary, at least for version 1.15.4.

[simon_ldt]

That's not always the case in my experience. Quite a lot of TV shows have audio gaps between segments (recaps and where ad breaks would have been when aired for example). I've had numerous shows do this but when I check the files at the time code it's fine and never happens mid scene or anywhere suspect.

Obviously for movies it's less likely to happen.

[preserve]

Obviously for movies it's less likely to happen.

A lot of movies use "seamless branching" with multiple segments, in which case it's highly likely to happen.

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AV sync issue in stream X at XX:XX:XX.XXX with duration of X.XXXms : ...

...which indicates a real problem with the rip (potential audio or video drops).

I would just add that when you do see these real errors, the degree to which they are a "real problem" will vary, as MakeMKV attempts to correct for them.

As you can see in the example below, MakeMKV keeps track of the ongoing "audio skew" and it gives 2 different indications, one message when it encounters an overlapping frame (of audio) but does nothing, and a second message when it has determined the audio skew is becoming too much and drops an audio frame to compensate.

Example from Harry Potter 1 and its primary DTS-HD MA Surround 5.1 English audio track, using MakeMKV 1.15.4:

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AV synchronization issues were found in file 'E:/Video/Harry Potter 1/Harry Potter and the Philosopher's Stone_t07_s00100.mkv' (title #8)
AV sync issue in stream 1 at 0:08:40.394 with duration of 10.458ms : encountered overlapping frame, audio skew is +10.458ms
AV sync issue in stream 1 at 0:10:19.243 with duration of 9.916ms : encountered overlapping frame, audio skew is +20.375ms
AV sync issue in stream 1 at 0:10:19.264 with duration of 10.666ms : 1 frame(s) dropped to reduce audio skew to +9.708ms
AV sync issue in stream 1 at 0:18:28.315 with duration of 5.416ms : encountered overlapping frame, audio skew is +15.125ms
AV sync issue in stream 1 at 0:18:28.330 with duration of 10.666ms : 1 frame(s) dropped to reduce audio skew to +4.458ms
AV sync issue in stream 1 at 0:53:18.403 with duration of 2.666ms : encountered overlapping frame, audio skew is +7.125ms
AV sync issue in stream 1 at 1:12:47.363 with duration of 0.541ms : encountered overlapping frame, audio skew is +7.666ms
AV sync issue in stream 1 at 1:13:48.882 with duration of 5.541ms : encountered overlapping frame, audio skew is +13.208ms
AV sync issue in stream 1 at 1:13:48.896 with duration of 10.666ms : 1 frame(s) dropped to reduce audio skew to +2.541ms
AV sync issue in stream 1 at 1:34:43.469 with duration of 5.333ms : encountered overlapping frame, audio skew is +7.875ms
AV sync issue in stream 1 at 1:37:33.222 with duration of 7.083ms : encountered overlapping frame, audio skew is +14.958ms
AV sync issue in stream 1 at 1:37:33.237 with duration of 10.666ms : 1 frame(s) dropped to reduce audio skew to +4.291ms
AV sync issue in stream 1 at 1:38:39.121 with duration of 10.166ms : encountered overlapping frame, audio skew is +14.458ms
AV sync issue in stream 1 at 1:38:39.136 with duration of 10.666ms : 1 frame(s) dropped to reduce audio skew to +3.791ms
AV synchronization issues were found in file 'Harry Potter and the Philosopher's Stone_t07_s00100.mkv' (title #8)

While in playback I haven't been running into noticeable problems, based on the above, my two main questions about this issue, which I previously posted, have been:

1) When dropping frames, is it an overlapping frame that's being dropped? The timecode of the dropped frame and the last overlapping frame don't match.
2) Why even bother to wait until the audio skew adds up, why not immediately drop each overlapping frame as it's encountered? This would seem a much cleaner solution.

[twl101]

I’m not sure if this is relevant, but I just wanted to let you know what happened to me and how I solved it. Again, not sure if it applies, so please forgive the newbie.

I just received The Season 4 set of The Expanse and had the same A/V sync errors after ripping the files. I only ripped each episode video, and none of the extras. I left all audio/subtitle tracks untouched. This is only my second time ripping blu-ray discs. The first had no issues.

After ripping, I played a couple of the videos using VLC and they played fine. I then used Handbrake to compress the files and then transferred the files to my HTPC, which is a Raspberry Pi running Openelec/Kodi.

When I tried playing the first file I got all kinds of A/V sync problems. I then went into the Kodi settings and under Player, Video, I turned on - Allow hardware acceleration - OMXPlayer. The files now play with no sync problems.

Almost forgot, this was on v.1.15.3. I haven't tried 1.15.4 yet.

I decided to rip a couple of the videos again, one with no subtitles, and one with. The one with no subtitles gave no A/V sync error but the other did. After converting both with Handbrake, they both had the A/V sync problems as before on my HTPC, but no problems when I enabled Hardware Acceleration in Kodi.

Again, forgive me if this information is irrelevant.

[hauntinghelix]

So are these AV synchronization messages actually an issue?

I am ripping Death Note Discs and every single disc have these sync issues nearly around the same times. Here is Disc 4 out of 5.

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AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 0:23:00.298 with duration of 373.333ms : 35 frame(s) dropped to reduce audio skew to +5.125ms
AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 0:45:57.386 with duration of 373.333ms : 35 frame(s) dropped to reduce audio skew to +9.083ms
AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 1:08:53.557 with duration of 384ms : 36 frame(s) dropped to reduce audio skew to +2.625ms
AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 1:31:50.634 with duration of 373.333ms : 35 frame(s) dropped to reduce audio skew to +6.583ms
AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 1:54:47.637 with duration of 373.333ms : 35 frame(s) dropped to reduce audio skew to +8.625ms
AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 2:17:44.266 with duration of 384ms : 36 frame(s) dropped to reduce audio skew to +2.041ms

What I mean "nearly" is that on disc 3, the AV sync issue would be:

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AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 0:22:57.376 with duration of 373.333ms : 35 frame(s) dropped to reduce audio skew to +2.041ms
AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 0:45:54.464 with duration of 373.333ms : 35 frame(s) dropped to reduce audio skew to +6ms
AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 1:08:51.392 with duration of 384ms : 36 frame(s) dropped to reduce audio skew to +6.125ms
AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 1:31:48.384 with duration of 373.333ms : 35 frame(s) dropped to reduce audio skew to +8.166ms
AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 1:54:45.600 with duration of 384ms : 36 frame(s) dropped to reduce audio skew to +4.333ms
AV sync issue in stream 1,2,3,4,5,6,7,8,9,10,11,12 at 2:17:40.469 with duration of 384ms : 36 frame(s) dropped to reduce audio skew to +0.166ms

Notice the problem occurs right around 0:23
By the way, this time is very near when one episode ends and another begins.

I don't notice any AV discrepancies while watching. Is it okay to ignore this? Thanks.

[Red Devil 24]

Example from Harry Potter 1 and its primary DTS-HD MA Surround 5.1 English audio track, using MakeMKV 1.15.4:

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AV synchronization issues were found in file 'E:/Video/Harry Potter 1/Harry Potter and the Philosopher's Stone_t07_s00100.mkv' (title #8)
AV sync issue in stream 1 at 0:08:40.394 with duration of 10.458ms : encountered overlapping frame, audio skew is +10.458ms
AV sync issue in stream 1 at 0:10:19.243 with duration of 9.916ms : encountered overlapping frame, audio skew is +20.375ms
AV sync issue in stream 1 at 0:10:19.264 with duration of 10.666ms : 1 frame(s) dropped to reduce audio skew to +9.708ms
AV sync issue in stream 1 at 0:18:28.315 with duration of 5.416ms : encountered overlapping frame, audio skew is +15.125ms
AV sync issue in stream 1 at 0:18:28.330 with duration of 10.666ms : 1 frame(s) dropped to reduce audio skew to +4.458ms
AV sync issue in stream 1 at 0:53:18.403 with duration of 2.666ms : encountered overlapping frame, audio skew is +7.125ms
AV sync issue in stream 1 at 1:12:47.363 with duration of 0.541ms : encountered overlapping frame, audio skew is +7.666ms
AV sync issue in stream 1 at 1:13:48.882 with duration of 5.541ms : encountered overlapping frame, audio skew is +13.208ms
AV sync issue in stream 1 at 1:13:48.896 with duration of 10.666ms : 1 frame(s) dropped to reduce audio skew to +2.541ms
AV sync issue in stream 1 at 1:34:43.469 with duration of 5.333ms : encountered overlapping frame, audio skew is +7.875ms
AV sync issue in stream 1 at 1:37:33.222 with duration of 7.083ms : encountered overlapping frame, audio skew is +14.958ms
AV sync issue in stream 1 at 1:37:33.237 with duration of 10.666ms : 1 frame(s) dropped to reduce audio skew to +4.291ms
AV sync issue in stream 1 at 1:38:39.121 with duration of 10.166ms : encountered overlapping frame, audio skew is +14.458ms
AV sync issue in stream 1 at 1:38:39.136 with duration of 10.666ms : 1 frame(s) dropped to reduce audio skew to +3.791ms
AV synchronization issues were found in file 'Harry Potter and the Philosopher's Stone_t07_s00100.mkv' (title #8)

While in playback I haven't been running into noticeable problems, based on the above, my two main questions about this issue, which I previously posted, have been:

1) When dropping frames, is it an overlapping frame that's being dropped? The timecode of the dropped frame and the last overlapping frame don't match.
2) Why even bother to wait until the audio skew adds up, why not immediately drop each overlapping frame as it's encountered? This would seem a much cleaner solution.

I just Started Using MakeMKV to rip my BD collection and I have the same question as you do.
My Avatar collector's extended edition use quite a lot of seamless branching, I end up with a log similar to yours.
I would be nice to have an answer to those questions.

[karbre]

2) Why even bother to wait until the audio skew adds up, why not immediately drop each overlapping frame as it's encountered? This would seem a much cleaner solution.

I too would like to know why it isn't handled this way. There is probably a good reason for it?!

[senpai92]

Hi everyone, I am on version 1.16.3 and I am also getting messages of A / V synch problems. Often these messages appear at the very beginning of the muxing. Is this a bug or a real problem? Should take this into account? Thank you for your feedback.

004008:0010 Problème de synchro AV dans le flux 2 à 0:00:00 d'une durée de 0.666ms : chevauchement d'images trouvé, le biais audio est de +0.666ms

[senpai92]

As I did not have any answers, I add a small precision, this message appears only when the dolby Atmos track is selected. Is this a false problem of MakeMkv? Because it is the only message that appears and nothing else until the end of the procedure. If someone comes by to enlighten me ... Thank you

[dcoke22]

It is really just an informational message and comes from the way discs are authored using seamless branching. I have a longer post on the topic here: viewtopic.php?f=12&t=22903&p=94894#p94894

The short, short version is MakeMKV is doing the right thing and those messages can be ignored.

[karbre]

It is really just an informational message and comes from the way discs are authored using seamless branching.

No, if the AV sync message appears at the beginning, it is not because of seamless branching, it is because the audio track and video track do not start "at the same time". I.e., the audio track starts a few ms before or after the video track.

To my understanding, MakeMKV does not always compensate for this in the resulting MKV (at least if these delays are below a specific threshold which I think is around 20ms) and thus the generated MKV has an AV delay as indicated in the message. If someone does not want this, he has to use another demuxer for such discs.

However, delays of 0.666ms as in the message above can definitely be ignored and are not noticeable. Some people say that everything under 20ms or even under 40ms can be ignored (MakeMKV seems to be coded with the idea in mind that everything under 20ms can be ignored). I personally am not of this opinion, as I am (sometimes) able to notice delays in the range of 10ms. Thus, for discs where MakeMKV issues a message that indicates resulting delays above 10ms, I tend to use another demux tool.

If you are not as sensitive as me, then you can just use MakeMKV without thinking too much about it.

[senpai92]

And does the fact that this only happens when the Atmos track is selected have anything to do with it?
Because when it is selected, it indicates this error to me on another track (French for example) and when it isn't selected no error for the French track. The biggest gap I had was 17ms at the very start if I remember correctly. When looking at the final mkv, with nvidia shield or zidoo z9x I don't notice anything but maybe with a more muscular installation (home cinema amplifier, atmos speaker etc ...) it gets along right?

If you are not as sensitive as I am, you can just use MakeMKV without giving it much thought.

What other demultiplexer do you recommend? And how can you be sure that everything is in sync?
Luckily it doesn't do it for all of my 4k movies

And thank you for taking the time to answer me