* Increase vbv-bufsize to 1/10 of requested bitrate. The previous value
was too low, which was resulting in poor encoding quality and failure to
stabilize at the requested bitrate. Setting to 1/10 of bitrate is a
good compromise, as it avoids quality loss but also prevents bandwidth
spikes far above the bitrate/vbv-maxrate.
* With vbv-bufsize set to a more appropriate value, testing shows that
the average bitrate vs client-requested bandwidth overshoots by ~20%.
Adjust for this scenario in the software encoding case only.
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