It is now possible to specify codecs other than VP8 and Opus. This
turns out not to be very useful, since VP8 is the only codec supported
by all browsers (in violation of the WebRTC spec, which mandates support
for H.264), and there is no good reason to use anything other than Opus
for audio.
We used to push a connection when we got all tracks. However, it may
happen that some tracks fail; in that case, the connection would never
get pushed.
We already send NACKs when a packet is missing. Under high packet loss,
however, the recovery packet might get lost two. Forward receiver NACKs
to the sender, but only after a delay and after checking that the packet
has not arrived in the meantime.
