Where the search paths list is not changed, using AC_PATH_PROG(S) has
no useful effects and makes manual override more difficult.

(Compare to Qt code using different search paths.)

Otherwise, it demuxes at max speed without allowing
user to change program

Some streams send clear padded data (probably
due to insufficient remaining data for encryption)

We'll only test on payload start then.

Since we can swap formats, some doesn't provide any or same values

Red over blue was against usability rules

Closed captions are in the same SEI user sections
as H264 according to the spec.

No functional changes.

In real use, there are few (typically only zero or one) listeners per
event type. In this case, the linear search through the listener groups
was actually slower than the linear search through the whole list of
listeners: it required one iteration per event type, even for event
types with no listeners.

(Note: using a hash table over the event type would make a lot more
 sense as an optimization.)

The distinction was rather vain, as the inner lock was almost never
held without the outer lock. The only case was adding an event callback
(but _not_ removing one). On the other hand, the distinction required
extra heap manipulations and memory copying for each event.