Hi list!
There seem to be some oddities in using ABR. The first thing I notice is
that because "abr_count" increases without bound, after a while the
weight of the bitrate history will completely swamp any change in the
current bitrate and the ABR adjustment will essentially stop happening.
This seems to be true in any mode (not just UWB) and perhaps a solution
is to cap "abr_count" at some value.
The other thing is that the ABR calculations are only done for the
highest submode, and in UWB that is a problem in that the ABR code
adjusts the bitrate by changing that submode's quality. This really
doesn't work well in UWB because that submode has very little freedom in
it's bitrate (only 4 or 36 bits/frame). A possible kludgy solution would
be to only perform ABR adjustments in the WB submode for both UWB and WB
modes. Although that would leave open the strange possibility that the
WB submode could be zero while the UWB submode was not, I don't think
that would hurt anything.
Let me know if I'm just reading this wrong, or if there's some better
solution. Thanks,
--John
