Another approach would be a general instruction to start at the minimum, and
increase until quality is good enough. If you step up and the picture breaks
up then step down again , as that's as quick as your connection can handle.
For the future we could look at giving some diagnostic feedback and advice if
the datastream is lossy or can't keep up. Perhaps an indicator that you can
click to reduce bitrate and reconnect the call? I guess if it was reasonable
to approximate adaptive bitrate through reinvites everyone would be doing it.
These are some of the reasons for which, in general, Skype is a better solution. It can change on the fly the bitrate and adapt the image parameters accordingly. I say "in general" because sometimes I was not satisfied with their choices. They can adapt the resolution, framerate... to a chosen bitrate ( determined upon analyzing the network conditions). It can actually do 640x480 at 40 kbits/sec (if I remember correctly) !!! This I something I could not do with h.264 or any other available codec.
Dragos