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TVS Audio Delay

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Patrick Murphy
TVS Audio Delay
on Oct 23, 2012 at 11:57:29 pm

It's nice that the BM TV Studio now has an audio mixer. The management of SDI/HDMI audio is a step forward. But how much analog audio delay is typical of this system? 1, 2, or more frames? It doesn't take much to spoil the show.

My guess is that it depends on how much work the TVS has to do to match various inputs. Is this a fair guess? I'm going to do some tests on my own, but if anyone has opinions, or data on the subject, I'd be grateful.



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Andreas Wojtaschek
Re: TVS Audio Delay
on Oct 24, 2012 at 6:00:21 pm

The delay of the TVS is exactly 1 frame if you use unsynced cameras. If you genock your cameras to the TVS it will be a delay of 1 line. (Actually you won't see any delay then)

Have in mind that every piece of gear that you use (converters, monitors and even your camera) can increase the delay by several frames. But the delay of the TVS is always just 1 frame from in to out.

In PAL land you should delay the audio by 40ms (because that equals 1 frame).

Cheers

Andreas

--

Entertainment Producer IHK
mindandvision


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Patrick Murphy
Re: TVS Audio Delay
on Oct 25, 2012 at 3:14:06 pm

So just to make sure I understand what you are saying...

One unsynced camera through the TVS is delayed 1 frame.

Additional unsynced cameras or other inputs will increase that delay. The amount of increase is directly proportional to the number of unsynced inputs.

In addition I'm guessing the following is true...
This only applies to AUX audio inputs.
Audio input as part of a SDI or HDMI input will stay synced with the video output of the device.



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Andreas Wojtaschek
Re: TVS Audio Delay
on Oct 25, 2012 at 4:49:40 pm

No sorry - you misunderstood me.

The delay is always 1 frame from input to output - no matter how much cameras you connect as long as the cameras are unsynced. If you sync all cameras to the TVS then you will have just 1 line of delay.

What you say about the audio is unfortunately not true. After the video signal is processed by the TVS and gets out of the SDI output you will experience a difference of 1 frame between audio and video. The audio will be 1 frame ahead of the video. That is why you should use a delay that delays the audio by one frame (in PAL 40ms in NTSC 33,3ms) before it gets into the TVS.

But even your camera can have a own delay from shooting the picture until the signal leaves the HDMI or SDI output. For example: Our HPX3600 has 2 frames of delay until the signal leaves the HD-SDI output. You would have to add that amount to the 1 frame of the TVS and end up at 3 frames of delay.

Cheers

Andreas

--

Entertainment Producer IHK
mindandvision


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Patrick Murphy
Re: TVS Audio Delay
on Oct 26, 2012 at 3:21:32 am

Many thanks for your clarification. I get it.
Your statement on camera delay is also most interesting.
It's not a factor I had considered before, but upon reflection it seems totally reasonable.
I'm working with Panasonics (AF100/AC160's), clearly some real world testing is in order.



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