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delay the audio output?

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Jeff Markgraf
delay the audio output?
on Aug 6, 2009 at 1:31:16 am

Hi all.

New FCP system (Quad core, internal raid, etc.) with the Extreme card (SD/HD/2k/HDMI).

All is well except for an annoying lag in the video on the Sony HD monitor (LMD-2450W).** I'm told it's an inevitable result of LCD monitors, even the broadcast monitors. The end result is audio that feels about a frame or two early.

Is there a way to delay the BM audio output by 1-2 frames to compensate? Or is there perhaps some other issue at play here? I'm monitoring via SDI.

**Hi Bob Zellin. I know, it's a terrible monitor, I couldn't get the company to dump it & by a decent monitor, so I'm stuck for now.

Thanks for any input.


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Ray Chung
Re: delay the audio output?
on Aug 6, 2009 at 7:18:49 am

Did you try tapping the audio monitor outputs from the monitor?



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Jeff Markgraf
Re: delay the audio output?
on Aug 6, 2009 at 6:18:18 pm

Audio monitoring is through the BM card's monitor out. SDI to and from the deck, and to the monitor. The monitor doesn't de-embed the SDI audio, so I couldn't listen to audio via the monitor. Are you suggesting that the SDI output is delayed relative to the card's analog monitor audio output? That shouldn't be...


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Ray Chung
Re: delay the audio output?
on Aug 6, 2009 at 10:18:36 pm

Not quite sure....I'm experiencing the same as you, except that I have a Multibridge Pro feeding a JVC DT-V120LU via the Multibridge's HDMI out into the JVC's DVI-D in....and there's a frame or so of lag behind the audio which I'm monitoring from the Multibridge's analog audio outputs. Apparently, on the JVC models with SDI in, the embedded audio from the SDI can be output from the monitor's audio outputs. But then again, maybe the lag/latency is inherent to the actual video processing/response time of the monitor's panel, so the monitor's audio out from the SDI may still be a frame ahead of the picture etc.

There was some third-party plug in that I tried a while back for adjusting audio output sync, but I couldn't figure out how it would work while in FCP. It really might just be due to an LCD video processing lag. Some people have changed the 'frame offset' in system setting from 4 to 6 with seemingly better results.


If you figure anything out, please post the results, thanks.



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Jeff Markgraf
Re: delay the audio output?
on Aug 7, 2009 at 12:01:12 am

Thanks for the input, Ray.

>>Some people have changed the 'frame offset' in system setting from 4 to 6 with seemingly better results.

Perhaps this is what I'm looking for. Is it intended to be used as a delay or advance for just this issue?

In the broadcast world, there would definitely be an audio delay patched into any feed (live remote, etc.) that had to go through a frame synch and/or DVE, so as to compensate for the 1 or 2 frame delay introduced. (Look on with horror at those multi-hop satellite remotes with 4 and 5 frame delays.)

I'd hate to have to use an outboard delay box just to get my audio in synch!

Hoping someone from Black Magic will weigh in here...


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Jeff Markgraf
Re: delay the audio output?
on Aug 7, 2009 at 12:23:55 am

Well, here are some interesting results.

Changing the frame offset from 4 (default) to 6 brings the external video perfectly in synch with the canvas (record) window on the computer monitor. Changing the offset to 8 appears to bring the audio into synch with the external monitor.

Now, of course, the synch when watching the footage through the viewer or canvas windows is quite off with these settings.

So the current choices seem to be:
6 frame offset = video playback that matches, with audio out of synch with external video monitor;
8 frame offset = video playback that is offset, with audio in synch with external video monitor;
4 frame offset = video playback is offset, plus audio is noticeably out of synch with external monitor.

I would guess that the 6 frame offset ought to work, except for the (presumed) inherent delay in the LCD display on the broadcast monitor.

This seems to argue for 1 setting for editing without external viewing (or with the broadcast monitor clearly out of synch), with a different setting for watching the broadcast monitor with audio in synch.

Yikes. Not really the way I'd like to work.


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Ray Chung
Re: delay the audio output?
on Aug 7, 2009 at 3:58:29 am

Another possibility is to hook up a CRT monitor to your Decklink's analog outs and check if you notice latency. If not, then it's probably the LCD itself.



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Jeff Markgraf
Re: delay the audio output-solution??
on Aug 21, 2009 at 11:04:00 pm

Finally, an apparent solution:

The system had been set up with the picture monitor setting as "extended desktop." Changing it to "last frame played" effectively brought the picture monitor into synch with the audio. (Actually, just a 1 frame offset.) I'm told this tells the computer that the video is being handled by the hardware, rather than involving the computer to process the video.

This setting is on the first page of the Decklink preferences pane. The pix monitor and the computer monitor are still offset, but that is apparently normal for this kind of system.

So there ya' go.


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Kevin Johnson
Re: delay the audio output-solution??
on May 7, 2010 at 7:35:01 pm

We've got that same Sony monitor and are experiencing delays of 3-4 frames in Standard Definition. In our Blackmagic HD Extreme setting, we are set to black (not last frame played). The offset in FCP doesn't appear to have any effect on external monitoring, only the preview window. Could this be a bug?

Running Decklink 7.6, FCP 7.0.2, Leopard 10.5.8.

In the monitor settings, there is a delay preference. 0 is out of sync, 1 is closer to sync, 2 is in sync however the monitor jitters between fields and is unusable.

Kevin Johnson

Autodesk Smoke Artist
FCP Editor
Washington, DC


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