Cross platform video / web conferencing solution

We need a cross platform video conferencing system. This video conferencing software should be real time, no delay in transmission of video and audio with following features : 1) Video conference can be possible with at list 25 to many participants. (At list 25 people can interact in two way video and audio, but many other person can see and listen all of them. 2) App features can be similar to g*o*o*g*l*e h*a*n*g*o*u*t or VOIP video conferencing similar to s*kype (Remove * to read correctly) 3) Worker shall ensure support for w*owza media server and c*++ rtmp server (Remove * to read correctly)...If it is web based; in case of voip conferencing use any standard voip conference server. 4) Video-Audio should be in sync form. 5) User can set video size as per his choice. Software should support 320*240, 640*480,720*576,1080P. Which can use 150 kbps, 225 kbps, 500 kbps, 700 kbps. 7) Echo cancellation support. 8) All cameras (USB and professional) should be supported. 9) Full support for all browser all OS including iphone/iad and android (We have android and iphone/ipad video player app which you could enhance for the purpose ) Deliverables : Worker need to upload full source code, instructions, docs and setup as well. Use of open source like webr#tc, o#penmeeting, etc., ok