HDMI timing settings for video cards and LKV373 / Jetson Nano

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G4WIM
Posts: 379
Joined: Thu Jan 29, 2015 8:36 pm

HDMI timing settings for video cards and LKV373 / Jetson Nano

Post by G4WIM » Sat Nov 16, 2019 8:20 pm

I run a Jetson Nano H265 encoder controlled by a Portsdown combined with LKV373 to convert OBS output from my PC for transmission.

For sometime I had been struggling to get the LKV and Jetson to play nicely and not drop frames / lock up.

I found that feeding the LKV direct from my 1080p camcorder that everything was much more stable and smooth.

Trying to mimic the same resolution and frame rate output from my PC video card led to dropped frames and video lock up - indicating there was something not quite right with 1080p output from the Nvidia video card.

I decided to try a custom setting on the video card and straight away noticed the HDMI front porch was set to 638 bits by default !

Using this calculator http://www.epanorama.net/faq/vga2rgb/calc.html I found on the web allowed me to tweak the PC video card front porch to 32 bits and in doing so greatly improved the stability and performance of the PC / LKV / Jetson combination.

I can now run 2Ms H265 at 1920 / 1080 24 fps smoothly for hours on end with no freezes or unwanted artifacts.

If you're having trouble with the LKV try checking your video card parameters and set them as per the calculator - it may just help.

73 Tim

g0mjw
Posts: 2327
Joined: Sat Sep 20, 2014 9:15 am

Re: HDMI timing settings for video cards and LKV373 / Jetson Nano

Post by g0mjw » Sun Nov 17, 2019 9:04 am

Hi Tim,

That is interesting. I have gone over to using OBS Record to send UDP directly as the LKV373 stopped working altogether after a driver update.

Sending UDP directly from the PC can be a much better solution if you have a fast H265 encoder on your PC as it will also work with Portsdown and the minimalist PC+Pluto with appropriate firmware.

I will experiment. The LKV373 is still useful for cases where you don't have a PC with a hardware encoder, or have another HDMI source like a camera and need to get images to the Jetson Nano hardware encoder. There is a programme Custom Resolution Utility (CRU) that allows messing with parameters, but handle with care!

Mike
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G4WIM
Posts: 379
Joined: Thu Jan 29, 2015 8:36 pm

Re: HDMI timing settings for video cards and LKV373 / Jetson Nano

Post by G4WIM » Sun Nov 17, 2019 10:32 am

Hi Mike,

sounds like you had similar problems to me with the LKV being temperamental and sometimes just plain broken !

For a test I set a scrolling banner on OBS then watch the decoded video on MT for any jerkiness on the scrolling text.

Changing the front porch has removed all signs of stuttering on the scrolling text - not sure why or what the optimum settings are but at least in my case it has helped significantly.

Setting the front porch back to where it was causes the problem to re-appear so clearly at least with my set up there's something going on there, just not sure what or why.

I really like being able to use the Portsdown to control the Jetson / Lime combo as it's so easy to change freq, FEC, encoder and symbol rate - imho the weak link has been OBS via the LKV - so being able to remove the LKV and send UDP direct to the Jetson / Nano while retaining the functionality of the Portsdown is my goal.

As a bonus the round trip latency is sub 2 seconds with the Jetson / MT combination.

Question then becomes is the Jetson Nano required if the PC video card can do the H265 / 264 encoding ?

The answer is probably that the Jetson is not required but switching between 264 and 265 means that a different recording profile on OBS would be required for 264 / 265

Of course sending H265 all the time would be one option.

I'd be interested to hear how stable your OBS UDP output is and presumably you're using IPTS input on the PD directly to the Lime ?

Maybe post your OBS settings ? My video card supports H265 encoding but not actually tried it yet.

73 Tim

g0mjw
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Joined: Sat Sep 20, 2014 9:15 am

Re: HDMI timing settings for video cards and LKV373 / Jetson Nano

Post by g0mjw » Sun Nov 17, 2019 11:02 am

I just tried and the LKV373 still does not work. Lots of people in the web mention Nvidia drivers are to blame. It works fine on all other sources. For the moment I have put it to one side, along with the Jetson. It will be useful when portable as then I won't have the powerful GPU. The Jetson with a Pi camera and audio source driven by a minimalist Portsdown is a good solution for portable. You can get down to 33ks 8PSK or 66ks QPSK 2/3 FEC and still have reasonable quality sufficient to send the exchange. The SNR gain from 333 to 66 is 7 dB which might make the difference. Going down to 66ks and 1/2 rate FEC DVBS2 is at least 10 dB better than 333k DVB-S and with H265 vs MPEG2 the video is comparable. Poor in both cases but good enough for a contest exchange.

The same setup can also do 333k with excellent audio and video.

Now off to listen to 144.750

Jabi
Posts: 66
Joined: Sun Jun 14, 2020 3:23 pm

Re: HDMI timing settings for video cards and LKV373 / Jetson Nano

Post by Jabi » Thu Feb 04, 2021 6:39 pm

Hello:
I have lost documentation of my LKV373, V4.0. Aucun have one manual? Or what is the IP of it when I have Reset? Sorry my poor english.
73,s de Jabi, ea2aru.

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