This module only works in YUV mode.
It looks for files in the directory named 0000.yuv, 0001.yuv, 0002.yuv, etc.
The file names _must_ by four digits followed by .yuv.
If some frames are missing, the yuv import module will try to find the next aviable frame until it counts MAXFRM (MAXFRM=10000).
transcode cannot autodetect the size of the frames, so remember to use the -g size switch.