ADS Technologies USBAV-708 INSTANT VIDEOMPX, User Manual

Page: 44 / 116

The
Guide
44
Bi
tra
te
m
od
e
MV
re
-us
e
During multi-pass encoding it is necessary to
pass the same source video through the
encoder two or more times.
One of the more computationally intensive parts of
encoding is motion estimation, where the encoder tries
to find vectors predicting the movement of each block
from frame-to-frame via the motion search. Since the
source video is similar for every pass, the motion vectors
should also be similar.
When enabled, the MV log records the motion vectors
found by the motion search during the 1st pass and re-
uses them during nth passes. Encoding time is thus
reduced because motion estimation need take place
only once.
For MV re-use,
Write MV file must be enabled during the Multipass, 1st pass ,
and Read MV file during each Multipass, nth pass .
QUICK GUIDE
MV re-use
After the 1st pass it is not legal to change any encoder option while Read MV
file remains enabled. If you wish to change options between passes you must
disable the MV file at that point.
MV re-use can offer reduced encoding times under Standard Performance/
Quality mode, but marginally reduces video quality.
Where time is not a priority best results are seen when no MV re-use is
enabled.
MV re-use has less significant effect on encoding duration when bi-directional
encoding is enabled.
MV re-use:
-mv <filename>
Filename is the MV log file name, fully qualified with a pre-existing path and
enclosed in parentheses. The default is “C:\mvinfo.bin” .