One of the most popular video codecs is made by DivX. Their codec
is based on the mpeg4 standard and supports the latest proven
technologies in video coding.
DivX recently came out with version 5.0 of their codec.
When the version 3 drivers appeared, they allowed the
user to specify the bitrate but not the quality level.
Specifying the bitrate means that you can control the
output video file size. It often has side-effects which
include the notorious block artifacts.
However, in many situations such as archiving video,
it is crucial to keep a certain quality level for later viewing.
Beginning with version 4, DivX included a quality level
setting which guarantees the specified output video quality.
From 4 tests done on DVD movies, we found that a quality
level of 95 should be suitable for most users in archiving video
and is certainly near DVD quality but at a quarter of the file
size.
One caveat: It is important to note that on large screens such as
those found in home theaters (i.e. greater than 300cm), even
a quality level of 95 will give a noticeable reduction in
video quality. Keeping the original mpeg2 streams is important
for true videophiles. |