Windows Graphics Capture only delivers a frame when the captured content
changes, so a static source makes gfxcapture output nothing at all. An
fps filter after it cannot help, since it has no later frame to
duplicate up to, and anything muxed alongside stalls as well.
Add a dup_frames option, like ddagrab has. When no new frame arrived
within one 1/max_framerate interval, output a new reference to the last
frame, or a black frame before the source delivered its first one.
Repeats are stamped with their deadline in the QPC clock, the same clock
as SystemRelativeTime, and the next deadline counts from the previous
one, so timer overshoot shows up neither in the timestamps nor in the
rate. A captured frame timestamped at or before the last output is
bumped to keep timestamps increasing.
The new option is on by default, since the current behaviour is arguably
surprising and clashes with how a lot of the filter chain and the
fftools work.
Signed-off-by: Rafael Henrique Gonçalves de Oliveira <rafaelh9six@gmail.com>
Co-authored-by: Timo Rothenpieler <timo@rothenpieler.org>
