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View Full Version : NDI Connection through Line of sight (Point to Point) Link



Danparo
02-10-2017, 01:16 PM
I am using a vMix NDI for my video production for a live event and in my production I have two vMix PCs one is used for production video Mixing and switching from cameras and playout video files
and the other vMix pc located at the transmission side and the link to that side is a Mikrotik Point to Point IP Radio line of sight.

Both vMix pcs are on the same IP address and One end of the Mikrotik Radio is connected to a Gigabits Switch and the other side is also the same . When pinging both Pcs is works and reply with TLL 45ms.

When the NDI output is active at the production end the other PC at the transmission end could see the NDI feed but the video keeps freezing whiles the audio comes well.

The point to point link is about (9km) from the Studio to there the Transmission is done at the DTT Head End.

what could solve the video freezing and also is there any better way to achieve this. or any better way to have this done.

PIZAZZ
02-10-2017, 01:38 PM
What are the results of a speedtest from the remote end?
www.speedtest.net

kanep
02-10-2017, 05:08 PM
I wonder if packets are being dropped? That is what it sounds like to me. If NDI needs to resend a packet, your ping time is higher than that of a video frame (33ms for 29.97 framerate), so there is no ability for the system to resend a packet in time if your ping is reporting 45ms. If the frame cannot arrive in time, the last good frame is held until it is able to receive a full frame in time.

Bandwidth could also be the issue, what video format are you working with? What bandwidth should the connection be able to support?

Danparo
02-11-2017, 08:56 AM
Thank you Kanep and PIZAZZ.

@ PIZAZZ I am not using internet I will same I am a LAN and from there the production is and where the transmission will be its a Point to Point Radio so am not able to the check with Speedtest.net on less there is any other way to go about it or how to be able to check the bandwidth from point to point apart from pinging with a bandwidth number eg: ping -l 1024 192.168.2.4 . to see the speed so far that is what I have been able to do and my link to have 10MB ping reply without lost. so if there is any other way ?


@ Kane
1. I think packets have been dropping and is there anyway that I can get this issue fixed

2. I am working for 108050i and that is what I am sending from where the production is to the vMix at the transmission end.

3. Bandwidth when I test the point to Point line it could give me 10GB and above and I could only get that when ping from one end to the other eg. ping -l 10240 192.168.2.4 and its replies and the TTL is 50ms

so now how can I optimized the work flow and if there is any other solution to help me achieve smooth flow.

kanep
02-11-2017, 11:28 AM
@ Kane
1. I think packets have been dropping and is there anyway that I can get this issue fixed

I have no idea how this radio system works, you really should talk to the manufacture to see if there is anything that will help.



2. I am working for 108050i and that is what I am sending from where the production is to the vMix at the transmission end.

That format can peak at around 100mbit/sec.



3. Bandwidth when I test the point to Point line it could give me 10GB and above and I could only get that when ping from one end to the other eg. ping -l 10240 192.168.2.4 and its replies and the TTL is 50ms

so now how can I optimized the work flow and if there is any other solution to help me achieve smooth flow.

TTL is 'time to live' which is different than the ping time. I get what you are saying, but just to make sure we are using the same terminology.

In 50 frame rate formats, a video frame is 40 milliseconds, you should see if there is anything that can be done to get the ping time below your time per frame. On my wired Ethernet network for example, my ping time is less than one millisecond between systems, this radio link is several orders of magnitude higher than what wired Ethernet performance would be. Even when I ping Google.com over the internet I'm getting pings of about 30 milliseconds, and that is over the public Internet!