Programming Ideas, Logics, Tips and Tricks

How Gmail Video Chat Works ?

Posted on 18. Nov, 2008 by Sajith M.R in webworld

Recently Gmail Introduced Video Chat. For a platform, to support the video chat you need to install the flash activex plugin.

You can get the plugin from http://mail.google.com/videochat

But when you click on Install voice and video chat button, Some of you see the page which shows

“The installer should complete in seconds.

If you are having trouble with the download, click here. “ 

But some other see a auto installer page which downloads the Setup.exe file and automatically start installation and prompts you to restart the browser.

Who did this installation without any security problem or violation and we saw a different window which shows the progress bar of the installation. This happens only when , if you have google tool bar installed on your browser , or google desktop, or google gears. For those browsers if the above three is not present, the previous message gets result , and which provide the direct link of the GoogleVoiceAndVideoSetup.exe

It is http://dl.google.com/googletalk/googletalkplugin/GoogleVoiceAndVideoSetup.exe

My Chrome browser does not support automatic installation. Because it is a new guest for my OS and the google additional plugin installation happend before its arrival. So Only Download and manual installation works in that case.

Then what the script exectued behind is 

window.google.update.oneclick.install (install via click) 

and 

location.href =  http://dl.google.com/googletalk/googletalkplugin/GoogleVoiceAndVideoSetup.exe (install manually )

Note the first bit of script window.google , A new object for google, which is created as the result of any one of the above mentioned google services. My Chrome Browser (Since he is a new member) does not know about the window.google (he knows the default methods like window.location, window.document)

Thats allabout the installation part. 

Now About the Video Chat. Obviously it is a flash based video chat mechanism , but the difference is it uses rtcp and udp protocol for video /audio chatting. Did you check the speed of your video chat ? Amaze  rite ?

Then lets check about the video chat request.

When you request someone for a video chat, google ajax posts the following data

req4_jid c2143377409

req4_json            ["jc","xyz@gmail.com","c2143377409",[["192.168.1.100","3801","video_rtp","dgE9SG8VMVdQFrYo","gyB0pRw5dkoEtq21","1","udp","0","local","0"]]]

req4_type          j

req5_jid c2143377409

req5_json            ["jc","xyz@gmail.com","c2143377409",[["116.68.66.85","3784","rtcp","iqV9/3HhhqkjQ4kp","wMSi7BsiOVNtnbJR","0.9","udp","0","stun","0"]]]

req5_type          j

Here xyz@gmail.com is the person , to whom you are going to chat. It sends the video_rtp protocol parameters. To know more about rtcp and udp go to: http://www.javvin.com/protocolRTCP.html

Here 192.168.1.100 is my local area ip (LAN) and 116.68.66.85 is my internet IP address and the numbers starts in 3000 are the port number for the protocol

In addition to this, google also sends its usual parameters like mouse movement detector (To know the state of a chatter, idle or busy / normal )

It also sends the cpu speed info to google server to know about the video processing time. And your bandwidth and speed of internet is already there in google’s hand (See my post on Gmail Architecture to know about the 1pix speed calculation method of gmail)

count    3

req0_evtype       mousemove

req0_time          263866

req0_type          i

req1_focused     1

req1_type          cf

req2_jid

req2_json          ["mf","mf1.0","1.0.2.0",2,{"caps":7,"cpuSpeed":1664,"cpus":2}]

req2_type          j

Gmail sends request for every 3 seconds, and if your counterpart accepts the video chat invitation, your chat iframe loads with a flash object tag .

<embed id=”flash_yj_c_player2″ wmode=”window” pluginspage=”http://www.macromedia.com/go/getflashplayer” type=”application/x-shockwave-flash” seamlesstabbing=”false” allowfullscreen=”true” allowscriptaccess=”sameDomain” bgcolor=”#000000″ flashvars=”dbg=true&ap=player&nm=yj_c_player2&cb=Recv_yj_c_player2&os=windows&plugin=true&” src=”im/media-player.swf?ver=1.1.6″ style=”width: 100%; height: 100%;” name=”yj_c_player2″ quality=”high”/>

And this flash application does the later works.  This flash application communicate with google media server with Real Time Protocol and your video chat happens that way. The flash activex plugin support helps in accessing your webcam and mic.  Good day , have a nice chat … 

Mail Me for more information

Thanks and Regards

Sajith

Tags: architecture, behind, chat, desktop, featured, flash, gear, gmail, google, rtp, toolbar, udp, video, work