Using WMASFWriter in a DirectShow filter graph generates a video which pauses at each keyframe interval

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Andrew Dodman

Jan 31, 2012, 6:37:35 AM1/31/12
Hello all,

I am attempting to create a DirectShow source filter based on the
pushsource example from the DirectShow SDK. My source filter
essentially outputs a set of bitmaps, each of which typically lasts
around 600 milliseconds, to a video. I have set up a filter graph
which uses Async_reader with a Wave Parser for audio and my new filter
to push the video (the filter is a CSourceStream and I populate my
frames in the FillBuffer function). These are both connected to a
WMASFWriter to output a WMV.

What I am finding is that at times corresponding the keyframe interval
the video pauses for a second or two. This seems to be worse at HD
resolutions, thought that could be a red herring. What kinds of things
might be causing this? Is it related to how often I allow FillBuffer
to be called (my frame rate is 30fps, so I end up with the same bitmap
being repeated for several frames)?

Many thanks,

Andrew Dodman

Jan 31, 2012, 8:00:57 AM1/31/12
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