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Latency RTSP vs. NDI

Hi there, 


Recently, we bought two VL-ZCams to provide a livestream for our church. These cams are not equipped with the NDI protocol, but the video is being transmitted by RTSP. The RTSP-stream is set as an VLC-source into OBS. All the hardware is running on a dedicated gigabit-network.


Last days I am Google-ing for solutions to minimize latency. Most of the reactions on internet are speaking of latency around 100-200 ms for different setups with NDI-cameras. In our case there's a latency of almost a second. Is it because of not using NDI, but RTSP? 


Thanks in advance!


Thomas

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Hi Thomas,


Congratulations on the two (2) new ZCams!


The latency you're seeing is definitely well above average and is definitely not to the unit operating with RTSP instead of using NDI.


The average latency you;ve identified is spot on 100ms - 200ms with a number of factors at play.



In an attempt to get to the bottom of this I am hoping to gain a bit more insight into your current network and PC setup...


Network Questions

  • What mfg and model modem is being used?
  • Is there is a router, separate from the modem with a mfg and model you could share?
    • Is the router, or modem / router, supplying DHCP addresses?
  • After the modem / router how many switches are on the "network"? and what mfg and model are they?
  • Are there any wireless access points being used and if so what mfg and model are they?


PC Questions

  • Do you know what the specifications (CPU, Memory, SSD / HDD, GPU) or mfg and model of the PC you are using?
  • Is the PC operating on hardwired network, WiFi or both?
  • Does the PC have a static IP or is it using DHCP?
  • When you are running OBS with the camera(s) connected what is the resource utilization looking like?


OBS Questions 

  • What are you using for the ingest settings in OBS for each camera?
  • What are you using as the output stream settings?


Camera Questions 

  • What is the current RTSP stream configuration from the WebUI?
  • Is the camera operating on a static IP or DHCP??
  • What firmware version is the camera operating on?



I am hoping with some, or all, of the answers above we can begin to narrow in on the root of your latency issue.


We look forward to hearing from you again soon.



PTZOptics Support Information

Phone: 1-800-486-5276 x.1004

e-Mail: support@ptzoptics.com

Ticket: https://help.ptzoptics.com/support/home

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Hi Matthew,


Thanks for your response. It will take a little more time to gather all the required information. The reason is that our church is located in a shared building. We share the internet connection with another company. I'll have to ask another company for i.e. the router specs (we'll work on that. One of our church members is requesting a seperate internet connection at the telecom provider, so in the future we have our own dedicated internet connection/network)


But, for now I have some other information:


Network

  • Starting from the internet connection (router) of the other company, there's a cat6-cable plugged in a Netgear GS108PEv3 switch. I'm still learning, I watched a video from PTZo where some recommendations are given about the switch. Tonight I'll go to the venue to check settings of this switch (like: enabling mDNS/IGMP snooping and disabling jumbo frames)
  • In our network there's one wireless AP (Draytek; VigorAP 710)

PC
  • HP z240
  • Intel i7-7700K @4.20 GHz
  • 24 GB RAM
  • NVidia Quadro P2000
  • SSD hard drive (mfg/model for now unknown, i can check tonight)
  • The pc is hardwired to the Netgear switch (cat6 patch cable)
  • I'm not sure if the pc is using a static IP or DHCP. I'll check tonight (i guess static is the preferred option)
  • I don't understand your question 'what is the resource utilization looking like?'. Do you mean the picture quality, smoothness, etc? The picture quality is good (no fuzzy video), but a little bit delayed.

OBS
  • The cams are sending the video by RTSP to the network. In OBS i installed the VLC plugin (64bit), so the camera's still serving footage, even if the cam is not active in the program monitor in OBS.
  • Output stream settings: 1920x1080@25fps; de-/encoding using NVENC (instead of x264); bitrate of 2500 kbps

Camera
  • RTSP config: Last days I found your chart with RTSP settings for different resolutions. Tonight I'll change the settings of both camera's using these numbers.
  • The cams are set on a static IP-address. I used the IP-configurator form your site
  • Tonight I'll check the firmware version on both cams.

So, a few settings/specs are coming soon. To be continued ;)

Thomas
Hi Matthew, A whole bunch of questions, some of them are hard to answer (because we share the router of another company). So I took the practical way and made a ‘dry’ setup: - VL-ZCam (With recommended settings for bitrate, etc) - ZCam —> Cat6 —> TP-Link Archer 1200 (recommended hardware) - TP-Link setup using the PTZOptics Youtube-tutorial - TP-link —> Cat5e —> PC - PC is running VLC with Network Source using the RTSP-stream. After soms trial and error I discovered that the IPTV-setting on the router (‘IPTV’ on LAN3 and LAN4) is not working. I think it’s because of not having NDI. When I connect the camera on LAN1 (‘Internet’ instead of ‘IPTV’), it is working, but still with about 1 second latency. I was wondering if there are some other settings I have missed? Thomas

Thomas, have you gotten any further with your latency issue?  


I have a web cam (logitech), web cam embedded on my laptop, and an NDI camera in addition to the PTZOptics 20x camera.  I am also using RTSP and am also seeing about 1 second of latency where I don't on the NDI camera.  My camera doesn't natively work with NDI without a pricey license (no thank you).  I'm just wondering if you found any magical configurations that helped you with your latency?

Hi Gary, After a few tries we jumped to vMix. In vMix it’s possible to select ‘Low latency’ at the input settings. The thing is, you’ll need a very steady network to get a smooth stream without buffering. Later I saw in OBS also a setting for network buffer (default was I guess 400ms). When turning this buffer down (f.e. 120ms) it worked also pretty fine

To reduce RTSP latency in OBS use the gStreamer plugin instead of the built in Media source.  More details here: https://obsproject.com/forum/threads/rtsp-stream-from-ip-camera-delay-in-input-in-preview.112518/post-488456

I'm wondering what the recommended gstreamer plugin pipeline settings in OBS would be the PTZ Optics 30x SDI camera? 

I have the gstreamer plugin working in OBS, but I'm noticing no improvments of latency. It's about 1250ms with the regular OBS source.

Assigned static IPs in the same network block 192.168.0.2xx plugged into the same switch.

Thanks!

Hi Michael,


Do you know if you have the NTP, Network Time Protocol, option enabled on your PTZOptics camera?


This can be found in the Network Section of the cameras Web Interface, once enabled it will like help with your latency issue.


You can find a full article on using this feature and it's benefits below


https://help.ptzoptics.com/en/support/solutions/articles/13000083024-synchronizing-multiple-ptzoptics-ip-video-streams-audio


If you have any other questions please do not hesitate to return to the forums.

The last note in this thread is over 5 months ago, is there any additional information?  Did the time synchronization fix the problem or are there still issues?


Thanks.

From what we have seen, the newest firmware should have all the tools to sync up the camera feeds with the audio. This can still be tough doing on certain networks and it doesn't always work perfectly, but should be sync-able with the tools the cameras have, mainly the NTP server setting.  

I did get the gstreamer plugin to work and achieved a latency as low as 250ms compared to 1250ms without. I found it a bit tricky to get working without a guide.

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