Plugin Delay Compensation when syncing over IAC to Video Slave/ProTools

[boomboom888]

Hello,

 

Wondering if anyone has encountered this. I'm able to use both VideoSlave and ProTools for hosting video and playback on the same machine, through VideoSlave's ports or through IAC for ProTools.

 

That's all well and good, but as soon as I begin adding plugins in Logic the offset increases and there's a delay. I've monitored this by using the same video/audio in VideoSlave and ProTools and referencing against the same file played back in Logic. I've adjusted the Plugin Latency Preference, usually set on All. Ozone 8 seems to be a culprit here, but even with other plugins the cumulative effect becomes really noticeable.

 

Are there any known tips for adjusting sync so that the video host will receive it and be accurately in line with the Logic playback? Is it better to use a hardware MIDI interface to loop MTC/MMC back on a port there, rather than IAC?

 

Thanks!

[Dewdman42]

interesting, I'm surprised to hear that VideoSlave is not maintaining sync...and that is problem!

 

No I don't think a hardware midi would help.

[boomboom888]

Thanks Dewdman...

 

I'm able to create sync by going into Preferences, MIDI, Sync and adjusting the "Delay MTC Transmission by..." amount to a negative value. (About -280ms)

 

Did previous versions of Logic allow this adjustment to take place automatically, depending on the Session? Is there a way to do that in 10.4.8?

 

Thanks.

[Dewdman42]

That sync setting is not related to PDC at all, that's just a way to compensate for any general delay in your midi interface or IAC midi signal.

 

The fact that its going out of sync when you start adding latent plugins to your mix...is another matter though...and could very ell be a bug in LogicPro, but in order to determine that we'll have to try to dig deep and make sure there isn't a way around it.

 

I have observed weird issues with PDC when using an external midi track, but then the same project using External Instrument to send the midi handles all the PDC perfectly. However, LogicPro's MTC sync stuff, is not using External Instrument, its sending the midi directly from LogicPro's transport in some way. In theory, it should be sending the correct clock, but its possible that this aspect of LogicPro is not adjusting its internal MTC clock send along with everything else that normally gets adjusted by PDC.

 

Another thing that can help here is to understand exactly the track scenario that causes this problem to happen. I'm guessing, probably you have some AUX channels with latent plugins that cause the problem, whereas latent plugins in Inst and Audio tracks are no problem. yes?

 

The better we can narrow and reproduce the problem exactly, the better bug report we can file with Apple....or with any luck maybe we'll find a mode where LogicPro will handle it properly.

 

I don't use VideoSlave unfortunately so I can't really test this myself, but I have been planning on getting it eventually, so this is of interest to me.

[Dewdman42]

I found this free MTC monitoring utility that might help while debugging this: https://github.com/Figure53/TimecodeDisplay

[Dewdman42]

Yea I setup the same scenario using that free MTC monitor above. I get the same loss of sync when a plugin with latency is put on an AUX bus. At this point I feel this is probably a bug.

 

In LogicPro preferences there are a lot of sync related options, so its always possible one of them will solve this, but I don't know enough about it.

 

There is this screen, which seems to imply that MTC will be aware of PDC...but.... as you found out also, putting a latent plugin on AUX seems to not work anyway....

 

 

One suggestion I guess is to just manage it manually for now. When you put a latent plugin on AUX bus, find out how much latency its adding and the manually set the delay parameter on the above screen...There are numerous sync related settings, unfortunately I haven't been able to get anything to manually adjust the right way either, but i"m just kind of guessing around now, maybe someone will know better about it.

[Dewdman42]

Notice its the remote MTC monitor that is ahead of LogicPro. LogicPro is sending MTC clock too early, while delaying the rest of LogicPro due to the AUX bus latency.

 

 

So my guess is that the MTC clock is not being properly adjusted by LogicPro from AUX PDC (bug). However I tried adding MTC delay manually through various sync related preferences I found, and nothing I could do so far managed to line up the two clocks.

 

This is a major problem actually...if you're using VideoSlave or any other external video system..

[boomboom888]

Thanks for thoroughly looking into this!

 

I was seeing similar results using both VideoSlave and ProTools as video hosts. (VideoSlave has a free trial if you're curious to check it out - it's quite good.)

 

I'm not sure how to work around this for now other than adjusting it manually. I ran into it more using plugins on Aux channels as well as the Master Output. Though I will say that Ozone 8 Maximizer consistently adds about 280ms latency regardless of buffer size, that I can manage with the delay MTC setting.

 

I'm going to compare with how this works in Cubase.

 

Thanks again!

[Dewdman42]

The PDC problem is almost certainly related to only latent plugins on AUX or OUTPUT channels (include Master output).

 

I wasn't able to get the manual sync adjustment to fix it, but if you are able to, please let us know what you did.

 

PDC latency is totally unrelated to audio buffer size. Audio buffer is not related here.

 

The other work around, which you could do with VideoSlave I would guess, is that VideoSlave must have a smpte offset you can assign to the video. So when you know the amount of PDC latency being causes by AUX/OUTPUT plugins, then calculate the amount of SMPTE offset to put into VideoSlave so that it will line up with the MTC coming at it. Just a guess, without knowing the program.

 

You can find out the latency of any given plugin in LogicPro by hovering your mouse over the plugin button on the mixer...it will display a floating window with the amount of latency.

[boomboom888]

Thanks for the info - I'll look into that with VideoSlave.

 

Confirmed though that the latency is corrected when that same plugin is inserted on an audio track. When placed on an Aux or Master, it lags.

 

Between Logic, VideoSlave and the Timecode Display utility you shared (tapped thru IAC), the timecode is in sync for me, but the delay between the audio of Logic and VideoSlave varies depending on what type of track I have plugins inserted.

[Hendrik]

hi! I just ran into the same problem and found this very interesting conversation. May I ask if there are any news regarding this issue?

 

Best regards!

[boomboom888]

I haven't tried with the latest versions of Logic, but the problem remains.

This article from around the time of this original thread really lays it out that Logic can't be trusted with sync:

https://www.justaphase.blog/home/2020/4/23/daw-timecode-sync