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NDI bad quality?
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Rinsky  
#1 Posted : Monday, July 18, 2016 7:25:27 PM(UTC)
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I recorded my NDI output via ffmpeg and found out afterwards, that NDI was transmitting bad quality, very blocky with a lot of artefacts. I was recording with very high bitrate and tried the same settings with a decklink video input and had a great video quality, so the problem must be NDI.

I am using a 1 gbit switch and was also streaming to facebook live while using NDI sources, but never used 1gbit bandwidth.

Has anyone else experienced any blocky NDI video sources?
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kane  
#2 Posted : Monday, July 18, 2016 9:31:41 PM(UTC)
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I would try using NDI IsoRecorder (there is a free version from http://newtek.com/ndi/applications ) and see what happens. I'm not sure how you are getting NDI into FFMPEG, but I've use NDI IsoRecorder the quality is good, the compression should not be noticeable. If you are seeing major compression artifacts, something is wrong, but I doubt it is NDI.

Kane Peterson
NewTek
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stevespaw  
#3 Posted : Tuesday, July 19, 2016 9:25:06 AM(UTC)
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Did you watch it with NDI monitor on another PC for issues?

Steve
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Rinsky  
#4 Posted : Monday, July 25, 2016 7:06:47 PM(UTC)
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Thanks for your replies.

I just tested it with the same setup and same settings and the video quality was as good as if it is connected via video cables. When I was recording my last 2 live productions it always got blocky.

I don't really know what the problem can be. The only thing that's different is, that I did not connect any live cameras to the Vmix computer.

Could it be that the GPU was overloaded with 3 SDI inputs, 1 virtual copy of one of those inputs, 3 replay channels, 1 casparcg input via NDI from another computer and also sending the output via SDI and NDI at the same time?

The CPU was definitely not stressed out.

Setup:

CPU: i7 4930K
GPU: Nvidia Geforce GTX 760

Could it be that the NDI sources become blocky if the GPU is stressed out? If so, how do i find out when the GPU is stessed out?

Regards,
Patrick
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kane  
#5 Posted : Monday, July 25, 2016 9:21:48 PM(UTC)
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NDI is all CPU, so GPU shouldn't affect it, at least not directly. I don't know how vMix handles GPU resources, if it is doing something that lowers quality, then NDI will just have that to work with.

Only other thing that I can think of, you didn't happen to pick the low bandwidth option for your NDI sources in vMix? That would cause the quality to be lower.

Kane Peterson
NewTek
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Rinsky  
#6 Posted : Monday, July 25, 2016 9:45:29 PM(UTC)
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I already thought of the same thing, but sadly it was unticked, so it must be something else.
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admin  
#7 Posted : Monday, July 25, 2016 10:15:41 PM(UTC)
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Hi,

Can you send some screenshots to show the quality and also the exact recording settings used?
Can you also confirm the latest vMix 17.0.0.105 is being used?

GPU processing is exact pixel for pixel accuracy, so that will not be impacting quality in any way.

Regards,

Martin
vMix
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mjgraves  
#8 Posted : Tuesday, July 26, 2016 4:16:45 PM(UTC)
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Rinsky wrote:
I recorded my NDI output via ffmpeg and found out afterwards, that NDI was transmitting bad quality, very blocky with a lot of artefacts. I was recording with very high bitrate and tried the same settings with a decklink video input and had a great video quality, so the problem must be NDI.


What setting did you use for FFMPEG?

Was it ONLY the NDI sources where quality suffered?

Did the NDI streams look ok in NDI monitor?

It strikes me that FFMPEG is the more likely source of issues as it's encoding the recorded file. That's CPU intensive and inherently lossy.

I've yet to see NDI cause any issue with image quality.
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