Dialogue and video out of sync?

[spenedit]

Howdy,

I have a fairly large session running PT 12.3 native HD. I have a video (H.264) running, (1 reel, 15 min long.) Frame rate of the video matches my session. The window burn time code matches the time code in my session. The 2 pop on the dia track matches the 2 pop in the video, and then... the dialogue is out of sync on playback. It seems like the video is about 4-5 frames behind the audio. I've tested this on other systems, 12.3 non HD, PT 11 HD, and they play back fine, no problems. So, I know it's not the audio itself, but something with my system. Where should I begin to troubleshoot this?

[Dan Smith]

First would be transcode you video to a preferred codec like DNxHD or Pro Res. Then start troubleshooting from there. Some things to start with:

Have you measured your video offset? Catchin sync is a good app for setting this.

Do you have delay compensation enabled?

[Leverson]

The first thing I'd suspect to be the culprit is the H.264, that's not a good working medium. Try transcoding the video to ProRes (I usually prefer ProRes Proxy) or DNxHD (I usually prefer DNxHD36). Both of those formats will play back better than a compressed H.264. Either Apple's Compressor or MPEGstreamclip can convert (at least to ProRes).

The next thing I'd check is your video sync offset delay settings in Pro Tools. If you have a 2 pop check to make sure that is in sync, your delay settings could be a factor.

Or last but not least it could have been delivered to you off, the picture editor may have bumped all the dialogue over by a few seconds on accident, or there could have been a problem with the OMF export or the previous Pro Tools editor might have accidentally ripple deleted something. EDIT: sorry I missed when you said it plays back fine on other systems. The likely culprit is one of the first two things or something weird with your delay compensation, although it is weird that the pop is in sync and the rest isn't.

If it's globally off by the same amount, and you've determined it's not your system setting, slide the dialogue all over until it's in sync again. If the offset amount seems to drift then you may have to dig deeper to see what the problem is.

This is also where head and tail pops come very in handy, as you can see visually if things are aligned on the timeline as well as see/hear if they are aligned on playback on your screen.

[spenedit]

Delay compensation is enabled, and I've converted the video to DNxHD and that does not solve the problem.

I could be wrong, but I was under the impression that video offset was if you were playing the video through an external monitor or tv, yes? I'm playing this video back on my computer monitor. Do I still need to set an offset?

If I go frame by frame, the start of the 2pop audio lines up visually with the (video) frame of the 2 pop perfectly. However when I start playback, there is a slight delay of the 2pop audio. If I take the video offline, the audio plays correctly (the 2 pop sounds immediately, as it should).

[diamondschwin]

It's entirely possible your computer display has a delay and needs an offset. Usually they are better than a large LCD TV but it's pretty much the same technology inside a computer display as a TV so it could be just as out of sync. That's why they sell special gaming monitors for video game users who wants the least about of lag possible in their displays.

[Chief Technician]

Originally Posted by diamondschwin

It's entirely possible your computer display has a delay and needs an offset.

This was the case with Pro Tools v10.3.10 and earlier. I would not be surprised if there is some latency with the video window (Command+9) in Pro Tools v11.x and later.

As for H.264, it is on the supported list. Being supported doesn't mean it is a good idea. The only H.264 I wouldn't balk at using would be the equivalent of Panasonic's AVC Intra. That is, video encoded in H.264 as an I frame for every frame. 99% of the H.264 files you receive have I (full) frames, along with B (backward predicted) and P (forward predicted) frames. This is what makes both consistent sync and processing everything else while playing H.264 a challenge.

[joachim]

Originally Posted by spenedit

...Do I still need to set an offset?

https://www.gearslutz.com/board/post...-question.html
Post #8.

Nice cheapo trick from "iluvcapra" to get a rough idea about the offset.
I used a GoPro with 100fps to record the video of the monitor and the audio of the loudspeeker around the 2pop area.
GoPro video into a PT session with 25fps, measured the difference between to visual 2pop and the waveform of the acoustic 2pop in samples; difference divided by 4, calculated/converted to frames (or milliseconds).

[Leverson]

Originally Posted by joachim

https://www.gearslutz.com/board/post...-question.html
Post #8.

Nice cheapo trick from "iluvcapra" to get a rough idea about the offset.
I used a GoPro with 100fps to record the video of the monitor and the audio of the loudspeeker around the 2pop area.
GoPro video into a PT session with 25fps, measured the difference between to visual 2pop and the waveform of the acoustic 2pop in samples; difference divided by 4, calculated/converted to frames (or milliseconds).

Or if you don't have a SynCheck, use CatchnSync. It's inexpensive quick and accurate.

http://quietart.co.nz/catchinsync/

[spenedit]

OK, so I get the video offset, and maybe this is unrelated, but why is the video slowing down the start of my playback? When video is online, there is a little hitch to my playback. I.e. I press play and there is a very slight delay in the start of audio playback. If i take the video offline, playback is normal...

[Chief Technician]

Originally Posted by spenedit

why is the video slowing down the start of my playback? When video is online, there is a little hitch to my playback. I.e. I press play and there is a very slight delay in the start of audio playback. If i take the video offline, playback is normal...

This is the way it is with Pro Tools v11.0.0 and later. Avid is aware of this issue.