cfr: 0 (vfr), 1 (cfr), 2 (pfr) [see render.c]
pass: 0, 1 or 2 (or -1 for scan)
h264_level: vestigial boolean to decide if we're encoding for iPod
cfr: 0 (vfr), 1 (cfr), 2 (pfr) [see render.c]
pass: 0, 1 or 2 (or -1 for scan)
h264_level: vestigial boolean to decide if we're encoding for iPod