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Sorenson Video

Sarah McLachlan's "Building a Mystery"
Copyright Nettwerk Records/Arista
12KByte/sec: Sorenson Video (10KByte/sec, 240x180, 12 fps),
QDesign Music Codec (11khz, 2Kbyte/sec)

You will need QuickTime 3 to see this movie.

General Information

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).

More Sorenson Information

Architectures Supported
Basic vs Developer Editions

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. The Sorenson Video decoder is built into QuickTime 3 for both Mac and Windows. There are no licensing requirements or per-title fees.

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, Cons & Tips
  • 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.

  • 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.

  • For tips on choosing your data rate, using VBR, enhanced watermarking, and more, please see the Sorenson Video Tips page

Special Options

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
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
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

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