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Sorenson Video
One of the major advances of QuickTime 3 is the new Sorenson Video codec which is included
as a standard component of the installation. It produces the highest quality
low-data rate QuickTime movies.
The Sorenson Video Codec produces excellent Web video suitable
for playback on any Pentium or PowerMac. It also deliver outstanding quality
CD-ROM video at a fraction of traditional data rates, which plays well on 100mhz+ systems*.
Compared with Cinepak, Sorenson Video generally achieves higher image quality at a
fraction of the data rate.
This allows for higher quality, and either faster viewing (on the WWW), or more movies
on a CD-ROM (often four times as much material on a disc as Cinepak).
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More Sorenson Information
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Architectures Supported
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Basic vs Developer Editions
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There are two versions of the encoder (used to create video for playback): a "Basic
Edition" and a "Developer Edition". The Basic Edition encoder is built into
QuickTime 3 to allow the hobbyist to create video using Sorenson. The Basic Edition, however, lacks
important control features and special options that serious developers will need to control the encode
process. These features are only in the Developer Edition.
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The Sorenson Video decoder is built into QuickTime 3 for both Mac and Windows. There are no licensing
requirements or per-title fees.
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Sorenson has also worked closely with Terran Interactive to include advanced data rate control in the Developer
Edition of Sorenson Video which is only available when Media Cleaner is used.
This includes two-pass Variable Bitrate (VBR) Encoding.
VBR is a two-pass approach to encoding that dramatically improves picture quality in the final result. Check here for an example.
Pros
- Provides much higher image quality than Cinepak, with smaller files.
It is often possible to get twice the image quality at less than half the data rate.
- Tuned to work well from 2 - 100 KBps.
- Supports Media Cleaner Pro's variable bitrate encoding, which
provides the best possible results at any data rate.
Cons
- Playback of CD-ROM video requires faster computers than Cinepak
- Movies larger than 320x240, or at data rates above 100 KBps, do not play smoothly
except on high-end machines (such as a Macintosh G3). While picture quality is usually outstanding at
higher rates, you should test these movies on your target machines to determine if playback
performance is acceptable.
Tips
- For tips on choosing your data rate, using VBR, enhanced watermarking, and more,
please see the Sorenson Video Tips page
These features are only available in the Developer Edition.
- Temporal Scalability allows a movie to play at a high frame rate on powerful
machines, and fall back gracefully to a lower frame rate on slower machines. For example,
create a 30fps movie using this option for excellent full-motion playback on a fast Pentium. If played on a
slower system it will smoothly drop down to 15fps -- without the stuttering seen in other codecs.
- Automatic keyframes It is generally useful for each new scene within a movie to begin
with a keyframe. Like Cinepak, the Sorenson Video codec attempts to determine frames where new scenes
begin, and automatically make them keyframes. Unlike Cinepak, it allows the sensitivity threshold to be
controlled. Setting the sensitivity higher will increase the number of keyframes. Setting it too high
may raise the data rate and/or degrade overall quality. The default setting is usually fine.
- Media Keys are a new feature of QuickTime 3, much like passwords. By encoding a
video track with an access key, you may limit its viewing to people who have the required key.
- Data Rate Tracking allows you to control how strictly the target data rate is
maintained. Loosening this tracking can provide higher quality in situations where there
is some flexibility in data rates.
- Watermarking adds your custom watermark to a clip, like the station logos
often seen on television. The watermark is stored losslessly, so that it is reproduced perfectly
even at very low data rates. (Using this feature requires Media Cleaner Pro 3).
| Ideal source material |
Video, animations, QuickTime VR object movies |
| Supported bit depths |
24-bit color |
| Compression time |
Very slow |
| Temporal compression? |
Yes |
| Special features |
Developer Edition: Temporal scalability, Media Keys, watermarking,
supports Media Cleaner Pro's variable bitrate encoding
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| Encoder requirements |
PowerPC or Windows |
| Decoder requirements |
WWW: Any PowerMac or Pentium
CD-ROM: PowerMac or Pentium (100mhz* for playback of 320x240 @ 15fps)
*depending on configuration; 120mhz may be safer minimum for Pentium systems
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| Encoder availability |
Basic Edition included with QuickTime 3
Developer Edition available for purchase through Terran |
| Decoder availability |
Included in QuickTime 3 |
| Algorithm |
Advanced Vector Quantization (VQ) with Motion Compensation |
| Manufacturer |
Sorenson Vision, Inc. |
For more information, you can download the manufacturer's
data sheet.
If you have any comments or questions
about Sorenson Video, please contact us at
info@terran-int.com.
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