WMV files are usually decoded by Microsoft DMO decoder, built into WMP. As far as I know, it does not support playback rate modification. I may be wrong, I will look more into it.
You can try to install FFDshow and assign it to decode WMV files too.
As for the TS files, open a file, rightclick -> options -> filters and you should see all the filters used (splitters and codecs)
As for MPEG2 file length, each filter calculates this length in it's own way. Using framerate or using bitrate. If you acces 2 diferent decoders, one using bitrate, one using framerate, you will have 2 different lengths.
|