RTP video issue related to Jitter and packet loss depending on odd network status

3
votes

I'm a newbie software developer who develops SIP/RTP Voip software. For sure, I am using UDP protocol and Video Codec for this video is H264.

Since I am new to this Voip area, I am so confused and suffering painful network issues a lot.

I would like to ask experts something related to Network specifically dealing with RTP/RTCP issues on Jitter / Packet loss.

After SIP successfully creates media session, I get some issue for QoS.

Problems I am facing up is just like this below.

Wifi network(latency : 11.1m/s download speed : 14.9mbps upload speed : 3.27mbps) :
http://www.youtube.com/watch?v=epm01c6IT5Q&feature=youtu.be

3G network(latency : 26.4M/s Download speed : 1.94Mbps upload speed : 2.42Mbps) : http://www.youtube.com/watch?v=-iG156_wdQE&feature=youtu.be

as you see, through 3G that has low upload and download and unstable latency, video quality including video issue coloured green and video's delay is better than Wifi.

using 3G network slower than Wifi , I can always take better user experience than Wifi.

I didn't analyse RTP/RTCP packets deeply but the thing I can tell is ...

At the problem situation, when Wi-fi was used for the application, Jitter was strangely high enough and packet loss was obviously high as well.

To sum up,

  1. As you can see, video quality is better when I use 3G network slower than Wifi.
  2. When Wifi works there, Jitter and packet loss are obviously high as I can analyse packet using wire-shark on the receiver side.
  3. at that morning time, video problem(green pixel of video, video delay) was much more serious but as time went, at the afternoon and night, problem had been recovered a bit.

As far as I know, it would be related to network bandwidth and network congestion. I am not sure that it is proper diagnosis and also need to solution to this. I'm sorry that I have not enough background information yet.

Thanks.

1
networkingsiprtppacket-lossjitter
What's your question though? Network effects including packet loss, jitter and bandwidth will affect the quality of your media stream. To dig deeper with WireShark try using the Telephony->VoIP Calls and Telephony->RTP->Stream Analysis to find packet drops, out of order packets and jitter variations. – sipsorcery
Okay, I'll try. Basically, I need the possible diagnosis under the circumstance and resolution. Thanks – boraseoksoon
Problem is remote and local video view coloured green chronically and video delay that makes user interface worse while Voip software uses Wifi network. – boraseoksoon
I watched your video clips. The only thing that stands out to me is that the green screen you occasionally get looks to be the exact same green screen Windows supplies when a webcam is initialising. Can't say I've ever seen it other than when the camera first starts up though. Perhaps for some reason your code is not able to get samples from the webcam at the rate it is requesting and the gaps are being filled with the green screen. – sipsorcery

1 Answers

1
votes

You area going to have to look at the RTCP or RTCP-XR messages to see what is going wrong. If that fails then like the other posts have said you will need to use wireshark to determine what the issue is.

There is most likely a network layer issue that is causing this so do what you can to test your connection to the other side. A traceroute might be a good place to start to see what the difference is between how the 3G routes vs the wifi.

Wifi can have many issues related to jitter and packet loss that your cell network might not depending on your signal strength (and other things). If you can test with a hard wire connection then you can rule out wifi as an issue and if you still have issues it has to be network/ISP related. If a hardwired connection resolves your issues then you know it was the wifi and you can troubleshoot accordingly.

The green is most likely an artifact of the jitter/packetloss. Normally in the US, for voice, a ptime of 20ms is used. Which means that audio packets (and video if used) are send every .02 seconds. If your jitter is higher than 20ms or you have high packetloss or burst packetloss then you will likely see and hear distortions because the packets either arrive out of order and are dropped or are lost. The green screen is just one of many you could see depending on the app you are using. I work mostly with audio so I am sorry I can't be more helpful with the exact meaning of that artifact.