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Sync audio with video

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Michael Lin
Sync audio with video
on Dec 14, 2009 at 6:14:57 am

We recently purchased the Panasonic AV-HS400a and Datavision HDR-200 video recorder for a church live video switching setup. What I don't understand is how to sync the audio with the video since the HDR-200 only has analog audio inputs. I called up both companies and they both told me to add a audio delay unit. I feel like this still won't work since according to the AV-HS400a manual, every time you do a screen wipe or any sort of effect its an extra frame of delay. That means if I do 30 wipes I will get 30 frames of delay which the fixed audio delay I pre set will not compensate for. How can I sync the audio with video?


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Walter Soyka
Re: Sync audio with video
on Dec 14, 2009 at 5:33:50 pm

Your digital switcher's M/E (which allows you to wipe or process effects) introduces delay, but it's constant; it won't be cumulative every time you transition.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Michael Lin
Re: Sync audio with video
on Dec 14, 2009 at 11:35:19 pm

Thanks for your reply! Can you please correct my logic because I still don't understand. The total delay between audio and video should be about 2 frames at the end of 5 minutes if I don't do any effects or transitions due to normal processing time. If I do 5 transitions within the 5 minutes, from what I understand, I will get 2+1+1+1+1+1=7 frames of delay between the audio and video at the end of the 5 minutes.


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Walter Soyka
Re: Sync audio with video
on Dec 15, 2009 at 2:31:57 am

The total delay will be the same, 2 frames, regardless of the number of times you transition. It's not the act of mixing that creates delay; it's the presence of the mixer itself in the signal path. The switcher has a digital signal processor in its mixing unit. That processor takes input, processes the mix, and outputs. The time between input and output -- the delay -- is one frame. The mixer is constantly working one frame behind the inputs.

Add that frame to the additional frame of processing on input, and whatever processing (if any) is done on output, and you get the total delay of the system.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Michael Lin
Re: Sync audio with video
on Dec 15, 2009 at 5:22:14 am

OK I understand now. I originally thought that the effect will add addition delay other then the delay caused by the presence of the mixer. The manual says "When DVE effects (SQ, SL, 3D) have been used as the video effects, the output signal is delayed by +1F"

Thanks for clearing this up for me.


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