AVI File
Compression Information
AVI files are extremely large when uncompressed, so you will want to
compress your clips when you export them to AVI files for teaching files and
presentations.
Each computer can
have a different selection of AVI compressors available. ShowCase does not
install these AVI compressors on your machine; They came with the
operating system or sometimes with other media software you may have
installed. ShowCase provides a
dialog showing all compression options registered on your machine and allows you
to chose which to use.
Dr. Lars Thorelius, a
ShowCase customer from University Hospital in Linköping, Sweden,
uses an image compressor from DivXNetworks, Inc. to process
ultrasound images, producing AVI files with high quality and small file
size. If you would like to try DivX, you will probably want to try the
settings preferred by Dr. Thorelius (see below). Click
here to read Dr. Thorelius' article published on Aunt Minnie.com. You
can download the DivX
codec from their
web site. A free version of the codec is available.
Three
very common compressors are Microsoft Video 1®, Cinepak®
and Indeo ®.
Microsoft Video 1 should have been
installed as part of your Windows operating system. For
those of you who work on Macs, Cinepak is known for working well across different platforms. If Cinepak
is not available on your computer, you can order
CinePak on the web. (Use the link above.)
Compressors offer a range of "quality" settings. You
will probably want to experiment with different compressors and different
quality settings to decide a good balance between image quality and file size.
Quality vs Size
Performance is always a factor in deciding how much
to compress your images. Extremely large files may not play at full speed in
slideshows and AVI players. Test your files and find a good compromise between
quality and size that works on your computer for your specific application.
If
you are transporting your AVI files to play on another machine (eg:
taking a Powerpoint presentation to another site), keep in mind that the
other machine will need the matching decompressor in order to play your
AVI file. The 3 compressors mentioned above are widely available on
Windows machines. DivX Settings from Dr Thorelius
The
following
information
was
provided
by
Dr.
Thorelius
to
help
you
get
started
with
the
DivX
AVI
compressor
if
you
want
to
try
it:
The original DivX settings are for 2 hour movies...
Among
the
settings
fields
in
the
DivX
interface
there
is a
box
called
"Quick
confiq
CLI",
where
you
can
set
parameters
for
all
settings
in
one
line.
My
setting
for
high
quality,
25
frames/second,
5
second
long
clips
maintaining
small
file
sizes
(the
one
used
in
the
gallstone
article)
is:
-b1
2000
-key
300
-dr
10,2,10,10,20
-sc
50 -pq
5
My
setting
for
longer
clips,
providing
a
slightly
less
detail
but
still
keeping
the
files
reasonably
small
for
Internet
use,
is:
-b1
750
-key
300
-dr
12,3,10,10,20
-sc
50 -pq
5
My
setting
for
very
long
clips,
up
to
one
minute
with
8
frames/second
showing
dynamics
of
intravenous
contrast,
is :
-b1
300
-key
300
-dr
12,5,10,10,20
-sc
50 -pq
5
|
|
|
|
