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Connect Spark vMix Audio Sync workflow
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SHMD  
#1 Posted : Monday, October 16, 2017 8:54:12 PM(UTC)
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I figure the NDI forum is the best place to ask this question I have about the Connect Spark and vMix setting for audio sync...

I have added a connect spark and used it at a live event last night where we where running it on a private 5Ghz wireless network so we could move cable free through out the 8500 sqft room. (BTW the wireless ndi video was amazing all six hours with no issue all night - We had it set on Medium )

We had a simple and quick mobile 3 camera setup with 2 cameras on SDI and one of the SDI cameras provided the audio for the stream. We had a small delay on the the NDI input from the spark so I figured the quickest way to get the image and audio it in sync was delay my 2 SDI cameras the correct number of frames. I did this by making the adjustments to frame delay in the advance section for each SDI camera input, so they would be in sync with the NDI connect spark. The problem with procedure was the audio would go out of sync for all three cameras. So it seemed to me the audio was not changing with the frame rate delay? The video did seem to be in sync, was just audio that was an issue at this point.

I wish vMix had a feature where we could clap or make a quick tone sound and all the camera inputs would sync for these quick setup situations. (Teradek Live:Air has this feature)

So how do other vMix and Connect Spark users fix this sync issue when using a simple setup?

Thanks for any help on this one as I did not see any straight up answers in my searches.

-sheldon
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seb666  
#2 Posted : Tuesday, October 17, 2017 1:25:45 PM(UTC)
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SHMD wrote:
I wish vMix had a feature where we could clap or make a quick tone sound and all the camera inputs would sync for these quick setup situations. (Teradek Live:Air has this feature)

So how do other vMix and Connect Spark users fix this sync issue when using a simple setup?


I do clapping and record it. Then I check the recording and the delay and try to sync all inputs (Blackmagic SDI capture card, Spark HDMI and RTSP from PTZ cam).
The clapping feature from Teradek sound quite interesting... Does that work well?

If anyone has a nicer solution to this, I'm also interested. :)
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DWAM  
#3 Posted : Tuesday, October 17, 2017 2:09:41 PM(UTC)
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Hi

I think that mixing SDI/HDMI with NDI|HX or any other H.264 based input is not a good idea for multicam.

Spark, like RTSP, has latency and it can be variable over time. You will never find a satisfying setting.

Guillaume
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SHMD on 10/17/2017(UTC), RobLambert on 10/17/2017(UTC)
SHMD  
#4 Posted : Tuesday, October 17, 2017 2:31:05 PM(UTC)
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Well if I could just get it close to be OK for streaming... maybe NDI is not the solution I was looking for. I guess I will go back to SDI for now.
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SHMD  
#5 Posted : Tuesday, October 17, 2017 2:34:49 PM(UTC)
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seb666 wrote:
The clapping feature from Teradek sound quite interesting... Does that work well?

It works great on the ipad pro with 3 cameras coming in over wifi... just one quick clap and it syncs close enough that no one can notice an audio sync issue. So simple and fast!

-sheldon
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DWAM  
#6 Posted : Tuesday, October 17, 2017 4:46:54 PM(UTC)
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Quote:
maybe NDI is not the solution I was looking for.


I believe NDI is. But Spark is not "pure NDI" as Tim says, it's NDI|HX which is basically a Long GOP H.264 encoder sightly modified to be NDI compatible. And there is latency on all H.264 encoders due to the nature of this codec. H.264 is a distribution codec, not a production codec.

If you use NDI, not NDI|HX, you won't experience the same latency issue. Pure NDI is a production protocol (however it's more expensive than SDI).

Guillaume
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RobLambert on 10/17/2017(UTC)
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