DirectShow source filter

CodeGuru's snake sample prog doesn't work, it hangs
to register or unregister a filter (e.g. ball.ax):
regsrv32 ball.ax
regsrv32 /u ball.ax
then draw a filter graph using graphedt.exe
to view, connect ball -> video renderer
to create AVI file, connect ball -> AVI mux -> file writer
this works fine, but important questions remain
1) how do you run the filter chain without using graphedt?
2) how do you get the app to communicate the frames to the filter?
3) where does the source filter's GUID come from?

invalid pixel format

Ben C's Gateway won't run Whorld in DirectDraw mode: it gives the error DDERR_INVALIDPIXELFORMAT. He initially had DirectX 8.0, I upgraded to 8.1 but it didn't help. Checked the Display Settings, he had 24-bit 1024x768. Tried 640x480, didn't help. Try 16-bit color?

POINTF vs DPOINT

Using POINTF (e.g. for Pucker) saves 8 bytes in the RING struct, which reduces the disk throughput requirements for snapshot movies. It doesn't seem to measureably worsen CPU usage. The downside is trading 15 digits of precision for 7. For items that remain constant over the life of a ring (e.g. Pucker), it might not matter, but for items that are incremented per frame (e.g. origin), it definitely *does* matter.