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jpeg2RAW  
#1 Posted : Saturday, June 25, 2016 10:54:50 PM(UTC)
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Tonight I did some stress testing of recording on a separate PC from my main vMix machine. NDI takes up some CPU cycles, but all in all, my main vMix machine ran around 40% CPU (total per Task Manager) vs mid 50%. However, there are notable compression artifacts on the recording. I am thinking this is because I am recording in 1080p (which is what I want to record in), but the settings on my main vMix machine for streaming are set to 720p (this is what I want to stream at). Any way to stream from my main PC at 720p, but have the 2nd PC record at 1080p via NDI and not get the compression artifacts? In other words, can I send a 1080p NDI stream to a networked computer and stream to YouTube at 720p?


Mike
AElli  
#2 Posted : Saturday, June 25, 2016 11:44:41 PM(UTC)
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jpeg2RAW wrote:
Tonight I did some stress testing of recording on a separate PC from my main vMix machine. NDI takes up some CPU cycles, but all in all, my main vMix machine ran around 40% CPU (total per Task Manager) vs mid 50%. However, there are notable compression artifacts on the recording. I am thinking this is because I am recording in 1080p (which is what I want to record in), but the settings on my main vMix machine for streaming are set to 720p (this is what I want to stream at). Any way to stream from my main PC at 720p, but have the 2nd PC record at 1080p via NDI and not get the compression artifacts? In other words, can I send a 1080p NDI stream to a networked computer and stream to YouTube at 720p?


Mike


I'm recording 1080 using Newtek ISO'corder and I dont see any issues in my recordings, with Vmix preset at 1080. so I'm thinking it might be something in the upscaling.

A.
sinc747  
#3 Posted : Sunday, June 26, 2016 12:24:26 AM(UTC)
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Mike,

What are the specs of the two PC's especially the graphics cards?

I am doing almost exactly what you are talking about. My main PC (i7-2600K with Nvidea 750ti) is set to operate at 1080p in vMix. My 2nd PC (ASUS ROG i7 with Nvidia 970m) is also set to operate at 1080p in vMix. Main PC sends 1080p to 2nd PC via NDI. 2nd PC streams 720p and records 1080p. Main PC does all the production (green screen, videos, graphics, cameras, screen captures, etc.). Main PC runs about 45% CPU. 2nd PC about the same. Sweet setup.

Hope this helps.

- Tom
jpeg2RAW  
#4 Posted : Sunday, June 26, 2016 9:42:48 AM(UTC)
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I think the problem is my main PC has streaming settings of 720p and the recording PC is streaming at 720p (which should be fine) but is recording at 1080p. So the recording is not receiving enough data (720p vs 1080p).

Here are my Stream settings on the main vMix machine

UserPostedImage


Here are the Stream Quality settings. What bitrate should I use on the main PC if I change this to 1080p and send it to the 2nd PC via NDI?

UserPostedImage



Main vMix PC = PC1
2nd vMix PC = PC2
2 other PC's but not part of this question

PC1 specs:
Core i7 3770k OC to 4.0GHz
GTX 980 4GB video card
32GB of RAM
Multiple SSD's

PC2 specs
AMD Phenom II x6 - 6 core at 3.2GHz
GTX 960 4GB video card
16GB of RAM
256GB SSD
RoboST  
#5 Posted : Sunday, June 26, 2016 11:49:47 AM(UTC)
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In vMix, what about setting your Master Output Size to 1080p, keep your External2 at 1080p (configured for NDI out) and have your streaming (External) at 720p (looks like you can enable External2 for NDI as well).

Or, if possible, keep External at 1080p (configured for NDI out), External2 for streaming at 720p.
jpeg2RAW  
#6 Posted : Sunday, June 26, 2016 4:21:44 PM(UTC)
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OK, here is an example after I made PC1 streaming settings to 1080p.

This is from the main PC recording that is receiving a webpage from another PC (call it PC3) via NDI desktop. Recoding was in 1080p 50M video quality setting for FFMPEG


Cropped version of the webpage. Text is fairly clean with little compression artifacts

UserPostedImage



This is from PC2 which is receiving the output of PC1 via NDI. Recoding was in 1080p 50M video quality setting for FFMPEG


Cropped version of the webpage- note the compression artifacts in the chat text

UserPostedImage



Full shot of the webpage, reduced in size for reference only
UserPostedImage
sinc747  
#7 Posted : Monday, June 27, 2016 11:50:38 PM(UTC)
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jpeg2RAW wrote:
Cropped version of the webpage- note the compression artifacts in the chat text


Okay. I guess I'm blind as I do not see the difference. And how should an artifact in chat be caused by vMix? What am I missing?

- Tom
jpeg2RAW  
#8 Posted : Tuesday, June 28, 2016 12:12:09 AM(UTC)
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The screen grabs are from the recording, which was a recording of our webpage. PC1 (main vMix PC) is receiving the webpage via NDI from PC3. When PC1 records (as in the top shot) there are very few compression artifacts in the recording. However, when PC2 gets the Output of PC1 via NDI the recordings have compression artifacts, which can be seen in the second screen shot, most notable in text.

I have tested this for hours today and the results are always the same. Even tried it with PC4 receiving the output of PC1 via NDI and same result. Then had PC1 get PC2's output via NDI and same result, compression artifacts. These seem most notable when text is involved, like a webpage.

Local recording looks awesome, every recording on another machine receiving it's feed from another computer's Output via NDI has compression artifacts. As one last test, PC4 also gets a feed from PC1 via the Fullscreen output using AverMedia C985 cards in both machines connected by HDMI. When PC4 recorded the video from this feed, there were no compression artifacts.

Hoping there is something I am overlooking that can fix this.
admin  
#9 Posted : Tuesday, June 28, 2016 12:32:48 AM(UTC)
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Hi,

To confirm some points made here, the "vMix - Output" NDI source is always using the Output Size set in Settings -> Display
it does not scale down if the Recording, External are at smaller resolutions (such as for streaming) so it will always be at the highest quality possible.

It's hard to tell what is causing which artefacts in the screenshots provided, as these have been through many layers of processing, including to JPEG
for uploading here!

A more scientific test would be to do as follows:

1. Add in the desktop at full screen of the web page into PC1 from PC3 using NDI. Make sure no scaling, zooming or cropping is being used.
2. Create a snapshot of the output in PC1 using the snapshot (camera) icon in bottom right hand corner of vMix. Save as PNG.
3. On PC2 add in the "vMix - Output" from PC1 and take a second snapshot. Save as PNG.

Upload both PNG files for comparison.

The first should have a small amount of compression as is added by NDI.
The second should be more or less the same as the first, as NDI in theory should not introduce more artefacts over multiple generations.

If there is a big difference I can submit a bug report to NewTek for investigation.

Some final points on NDI:

* NDI does add some compression, similar in many ways to JPEG.
* If you zoom into a NDI source from the receiver, this may become more noticeable. In general NDI sources should be kept at full resolution
and apply zooming at the source instead (such as zooming the text in the web browser and making the window bigger)

Regards,

Martin
vMix
admin  
#10 Posted : Tuesday, June 28, 2016 10:53:53 AM(UTC)
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Good news guys!

Turns out there is a bug in NDI affecting desktop capture that results in lower quality than expected.
Should be fixed within a week or so....
jpeg2RAW  
#11 Posted : Tuesday, June 28, 2016 6:18:54 PM(UTC)
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Awesome!! Thanks so much Martin. I take it you don't need me to perform the test mentioned above any more. If so, let me know and I will glad to do it.

admin  
#12 Posted : Sunday, July 3, 2016 6:20:45 AM(UTC)
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Latest vMix and Desktop Capture just released includes a fix for this.
jpeg2RAW  
#13 Posted : Sunday, July 3, 2016 9:08:05 AM(UTC)
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Thanks Martin!
jpeg2RAW  
#14 Posted : Sunday, July 3, 2016 11:36:26 AM(UTC)
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Just upgraded all the machines and the vMix update has fixed the issue reported in this thread for me!!
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