Question regarding DirectShowSource and convertfps parameter [Archive]

stax76

30th January 2010, 23:34

What happens if convertfps = true is used but the source isn't VFR? Is the parameter just ignored? StaxRip sets convertfps = true no matter what and so far this didn't cause problems, are there cases where it is a bad idea?

IanB

31st January 2010, 04:59

With convertfps=true, DSS uses the DirectShow sample start time to map the sample to a frame number. For CFR content there should be an exact calculable relationship between the sample start time and the frame number, which is the framerate. Haali's DSS2 always works in this mode.

With convertfps=false, DSS just delivers DirectShow samples as consecutive frames. It ignores the DirectShow sample start time. Apart from when seeking, in which case it assumes CFR content of the specified framerate.

So for CFR content it does not make a lot of difference. The choice is mainly for dodging bugs in various DirectShow components you may be using.

For VFR content you need convertfps=true to be able to seek. With convertfps=false seeking is pretty much out of the question. But this does give the options of striping the DirectShow samples on a 1 for 1 basis, the sample time mapping needs to be derived by an external process.

In hind sight convertfps=true would have made a better default, but the option didn't exist when the code was first written.