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Sorenson gets
the Earth, Wind & Fire test for this article.
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review
JULY 19, 2001
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Sorenson Video 3 Basic
Video
CODEC for streaming media
by
Stephen Schleicher
Producer
sschleicher@digitalmedianet.com
Recently
Sorenson released the Sorenson Video 3 CODEC. According to Sorenson,
this CODEC is a vast improvement over Sorenson Video 2, giving
higher quality video at the same bit rate with faster compression
and making better use of VBR (variable bit rate). Currently,
Sorenson Video 3 is available in two forms; Sorenson Video 3
Standard Edition, which is included in the latest release of
QuickTime 5.0.2, and Sorenson Video 3 Professional Edition.
The Professional
Edition has many more features over the Standard Edition, including:
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Support
for alpha channel/chroma key
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Automatic
keyframes through scene change detection
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Bi-directional
prediction
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Support
for two-pass Variable Bit Rate (VBR) compression
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Block
refresh for packet loss correction
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Media
key support through secure encryption
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Compression
time packetization for error resiliency to packet loss
Of course
reading about Sorenson Video 3 gives you one impression. How
does the new CODEC actually work?
I haven't received the Sorenson Video 3 Professional Edition
as of this writing, but I was eager to check out the compression
quality available in the Standard Edition. If you follow DMN
TV, our streaming media show, which is part of the Digital Media
Net family, you may have noticed our latest edition is encoded
with Sorenson Video 3. Co-Producer Paulo de Andrade and I were
both amazed at the quality we were able to achieve with this
new CODEC and have decided to encode future editions of DMN
TV in this same format.
But
how much better is SV3?
I took some time this week to encode some footage supplied
by our friends at Art Beats from their Digital Film Library
to find out. I selected three clips for this test, each for
their unique qualities that can make compression and streaming
difficult.
From the Reel Fire 2 collection, I used the brushfire ignition
clip (RF202). This clip offers many hurdles for encoding,
including fast motion, detail and huge areas of contrast,
all of which which can make video compression a nightmare.
Because not everyone needs to compress video that has these
specifications, I compressed a cloud fly through from the
Cloud Fly-Thrus 2 collection (CF217). While this video clip
does have some drastic motion, that is typical in many streams
today, it also has subtle color and tonal variations that
can be lost when a video is compressed for the Web.
For the final clip of this test, I wanted something that combined
both of these, so I chose a canyon fly over from the Aerial
Landscapes collection (AL110A).
Incidentally, if you would like to view each of these in their
pre-Digital WebCast forms, visit www.artbeats.com
and use the reference numbers above to access the clips.
The Test
Because I only have access to Sorenson Video 3 Standard, the
only compression option available is the Basic compression
option. I previously have been using the Sorenson Video 2
Professional Edition, and the two have very different variables,
which can be set in Cleaner 5. To try and make the tests come
out as close to one another as possible, I used the secret
DMN TV compression settings that were used in the latest edition
of DMN TV (www.dmntv.com), which happens to be compressed
at 15 FPS at 240 x 180.
I also want to make it clear that these tests are being done
with the Standard version of Sorenson Video 3. Results should
be quite a bit different when using the Professional Edition.
I compressed these files three times; Sorenson Video 3 Basic,
Sorenson Video 2 Professional Edition with Basic settings
and Sorenson Video 2 in VBR.
The first round of tests were done at 300 kbps which is a
speed designed for viewers on a DSL or Cable modem. At this
rate, all of the video looks pretty good, with only slight
variations in the canyon and clouds example. The biggest differences
can be seen in the fire example. As far as over all quality
goes, Sorenson Video 2 Basic comes out on top in this example.
While it is slightly "fuzzier" than the other two,
it maintains the frame rate and contrast over the others.
Sorenson Video 2 VBR doesn't really come out well in this
series, and while Sorenson Video 3 Basic maintains the best
detail; for some reason the compression falls apart in the
last moments of the video. (I reran the compression several
times with the same results.) I should also point out that
no keyframes were set in these examples, which would have
improved the quality of each of these clips.
The big difference that can be seen in these examples is in
file size:
300
kbs file size results
Canyon
Sorenson Video 2 Basic 902KB
Sorenson Video 2 VBR 871KB
Sorenson Video 3 Basic 866KB
Clouds
Sorenson Video 2 Basic 536KB
Sorenson Video 2 VBR 513KB
Sorenson Video 3 Basic 498KB
Fire
Sorenson Video 2 Basic 472KB
Sorenson Video 2 VBR 373KB
Sorenson Video 3 Basic 566KB
Because of the fast motion, contrast and other aspects of the
fire video, Sorenson Video 3 Basic does fall behind the Professional
settings of Sorenson Video 2. However, Sorenson Video 3 Basic
does beat the other two in the other examples. While this may
not seem like big differences, remember these are short video
clips. Over the long run the file size savings will add up.
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Post
a comment or question in the Digital
Media Designer User Forum!
Stephen
Schleicher is the producer of DMNTV,
Digital
Animators and Digital
WebCast and is the host of the Digital WebCast forum at
the World Wide User Groups. He has taught at Fort Hays State
University in Hays, Kansas, and at the American InterContinental
University in Atlanta, Georgia, where he also ran his own
animation company, Thunderhead Productions. Stephen also freelanced
in the Atlanta area as a producer/editor for five years working
on everything from training videos to live shows.
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