Hi folks,
I have a quick couple of queries about frame stepping & KS filters. As I
understand it, frame stepping seems to work like this:
1… FGM changes renderer state to pause.
2… Checks filter can step, and requests step for X frames from
filter.
3… FGM changes state to play.
4… Filter should step through the required # of frames at the normal
playback rate.
5… Once filter has done that # of frames, it should send an
EC_STEP_COMPLETE to FGM.
6… FGM gets step complete notification, and then puts the graph back
in
the paused state.
Which means that my renderer has to implement the frame stepping
property
set, which it now does (many thanks to the guys on the dev driver group
got my GUID’s sorted!). Strangely, the filter graph manager seems to
invoke
the frame step property set on the *filter*, not the pin - but that does
not
concern me unduly at the moment.
However, the mechanism above means that my renderer also has to send the
EC_STEP_COMPLETE notification.
Perusal of the existing code indicates that (for example) the render
sends
an EC_COMPLETE notification by implementing the KSEVENTSETID_Connection
event set on a stream. The problem is that I can’t seem to find a
suitable
event set that would let me send the frame step complete notification.
Perusal of newsgroups / MSDN seems to indicate that one *could*
implement a
custom event set, but it’s unclear to me at the moment if I could tie
this
in to the notification that the filter graph manager expects.
Any ideas anyone?
MH.
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