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A/V Sync issues during playback

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JackAttack
A/V Sync issues during playback
on Mar 16, 2007 at 5:26:48 pm

When I playback from my timeline, I find that my audio preceeds my video by one frame. Clients and Producers have all noticed this. I'm hoping I can get some suggestions!

Here are the specs/issues:

Media 100 HD Suite v11.5.1
AJA Kona (OEM) 3 card and breakout box
My system is only a few weeks new... and I'm midway thru 2 HD projects and 1 SD project...

Media 100 Prefs >> Video Output:
Output: HD Suite
SDI 1: HD 1080i (although not in use)
Analog: HD Component
Component: SMPTE/EBU N10
SDI 2: HD 1080i (not in use)
Analog HD Std: HD 1080i

System Prefs >> Media 100 Video Out Control Panel
Same exact settings as above


Digitized: HD SDI with embedded audio into my system.
Therefore, I assume the video footage came into my system in-sync with the audio over the same cable.

Previewing a timeline / playback over a HD monitor:
On the breakout box, I'm using the "Monitor Out" BNC component connectors (far right on the breakout box, next to the deck control port) in HD to run video to my preview HDTV monitor. Simultaneously, I am using the RCA audio monitor ports (far right as well) connected to the same monitor.

I am getting a 1 frame sync issue when playing back from the timeline or Edit Suite. My initial thought is the card is having to convert one of the A/V signals (like a digital-to-analog conversion perhaps) during playback, causing the slight delay. The audio comes 1 frame ahead of its matching video.

NOTE: I am not referring to a difference between the external monitor and the record/source windows within Media 100. I'm referring only to an external preview HDTV monitor.

If trying to reproduce the symptom, my suggestion: if you could digitize via HD SDI with embedded audio, footage of a person speaking on camera, from far, medium and close-up angles. You will feel it's very slight, very very slight... but A/V sync is off...

Thanks!



Jacob (a.k.a. "Jack") ||
Creative Director / Co-Founder ||
LaunchPad Media ||
100 Galen Street, 2nd Floor ||
Watertown, MA 02472 ||
http://www.launchpad.tv


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Floh
Re: A/V Sync issues during playback
by
on Mar 16, 2007 at 5:32:43 pm

Ummm, the question is how your "Sync audio to" setting is set in the Audio Output prefs. The hardware up- and downconversion from HD to SD and vice versa takes some time. Therefore not all outputs and settings are in the same "sync". E.g. if you upconvert a SD timeline to HD during playback the upconversion will introduce a delay of 3 frames (I think it was 3 frames on HDx, not sure if it is the same on Aja). So if you monitor an SD timeline on a SD monitor connected to SD SDI out and on a HD monitor connected to the HD SDI out you will see that the HD monitor will be 3 frames later.
Therefore the computer needs to know which your "main" monitor is that gets synced with the audio. This can be done in the "Audio Output" pref by selecting the correct video out under "Sync Audio to".
I am not really sure if this is the problem you are seeing, but this is the first thing to check.

Floh


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JackAttack
Re: A/V Sync issues during playback
on Mar 16, 2007 at 6:15:46 pm

Ah! I see that setting, I had completely overlooked it.

However, I just set it to "analog" for sync.

I am still encountering the same issue - audio preceeds video 1 frame.

Jacob (a.k.a. "Jack") ||
Creative Director / Co-Founder ||
LaunchPad Media ||
100 Galen Street, 2nd Floor ||
Watertown, MA 02472 ||
http://www.launchpad.tv


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