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Audio Sync Issue with Aja Kona LHi

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Shawn Gaiero
Audio Sync Issue with Aja Kona LHi
on Dec 2, 2009 at 5:13:03 pm

Hey all,

I have recently installed an Aja Kona LHi card and added an FSI Monitor to my edit system. I am working with XDCAM EX 1080p 23.98fps footage and notice that the Audio is out of sync during playback. I tried changing the FCP Playback offset but can't seem to get Audio sync.

I have the monitor connected to the SDI out on the Kona LHi card and my speakers are connected to the XLR Analog outs on the Kona card. When I playback the timeline the audio from the speakers is way off. The audio coming through the onboard speakers of the FSI monitor is in sync but my external speakers are not.

Are there any other settings I should adjust?

Thanks in Advance,
Shawn

Mac Pro 2 x 3.2 GHz Quaed-Core Intel Xeon
6 GB 800 MHz DDR2 FB-DIMM
Internal Sata Drive
External OWC Esata Raid
FCP 6.06
Aja Kona LHi
FSI 1760W
Pair of Yamaha MSP5's


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Bram Desmet
Re: Audio Sync Issue with Aja Kona LHi
on Dec 2, 2009 at 7:02:50 pm

Hi Shawn, see here: http://forums.creativecow.net/readpost/8/1054376 for a related post. The audio on our internal speakers (and audio out) is automatically kept in sync, down to the millisecond, with the video regardless of what processing mode the monitor is in and what format is being fed to the monitor. With virtually all LCD based displays there will be some sort of delay and this delay is variable depending on source and monitor processing mode.

Bram Desmet
FSI (Flanders Scientific, Inc.)
http://www.FlandersScientific.com


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Rick Lavon
Re: Audio Sync Issue with Aja Kona LHi
on Dec 3, 2009 at 3:03:25 am

so are you suggesting to take the FSI audio out into a mixer and feed your speakers that way?



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Bram Desmet
Re: Audio Sync Issue with Aja Kona LHi
on Dec 3, 2009 at 4:29:22 am

Not necessarily, but it is an option. There are limits to using the audio out from the monitor:
1. It adds an unbalanced line-out on a mini-phono connector in your audio chain and this is a significant limit worth keeping in mind.
2. You can only monitor a maximum of 2 channels of audio at a time using the monitor's audio line-out.

However, on the plus side using the monitor's audio out as you suggest takes the guess work out of the audio offset value so audio sync is always perfect, down to the very millisecond (unless of course the audio is not in sync in the native source material).

What the majority of people not routing audio out of the monitor tend to to do is add the offset in the editing (or I/O card) settings. Most of the editing systems I've seen do this in terms of a specified number of frames/fields of delay. This is not quite as accurate as getting it down to the very millisecond, but you can get it dialed in this way within what is a perceptible limit. Getting this dialed in this way isn't all that difficult, but the thing to remember is that on virtually all LCD displays this delay will change depending on the resolution/framerate of the source. All that this means is that you may have to have different offset values for different formats (SD, 720P, 1080i, etc.). Also, there is not a universal delay between LCD manufacturers so it will vary from brand to brand and many times even model to model depending on video processing chip being used, panel technology type, processing mode the monitor is in, etc.


Bram Desmet
FSI (Flanders Scientific, Inc.)
http://www.FlandersScientific.com


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