One of the best new features of QuickTime 3.0 is the addition of two new codecs, Sorenson for video and QDesign Music for sound, that make it much easier to create high quality, low data rate movies for streaming on the Web. As you can see from the comparison below, they are much superior to the old guard, Cinepak and IMA.

The Cinepak movie on the right is one that I created from Apple's movie for use as an embedded logo on my QuickTime Movies page. I wanted it to have a reasonably low file size so that it would download quickly for the viewer. I arbitrarily picked 150 k as a good target size. Unfortunately, to reach that target, I had to make a lot of compromises. The frame rate was very low, there were a lot of compression artifacts, and the sound quality was severely compromised.

When creating the Sorenson movie, I aimed for roughly the same file size. With Sorenson, however, I ended up with much higher quality video at a much higher frame rate. And with the QDesign Music compressor, I got a wonderfully rich soundtrack with a very small data size.

The Sorenson movie below requires QuickTime 3.0
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Sorenson

vs.

Cinepak

 
 

143 k




95.2 k
6.8 k/sec
Sorenson
15 fps
136 x 160




42.8 k
3.0 k/sec
QDesign Music
16 bits
22.05 kHz
Stereo

 

File Size


Video Track

Data Size
Data Rate
Codec
Frame Rate
Dimensions


Sound Track

Data Size
Data Rate
Compressor
Bit Depth
Sample Rate
Channels

 

139 k




92.8 k
6.6 k/sec
Cinepak
4.9 fps
124 x 148




46.2 k
3.3 k/sec
IMA 4:1
16 Bits
6 kHz
Mono



Tips for Sorenson

Sorenson is an excellent codec for low data rate movies, but the trick is that you have to limit its data rate, otherwise it won't be much better than Cinepak. If you're exporting a movie in MoviePlayer (with QuickTime 3 Pro), use the Options and check the box to Limit Data Rate. For movies on the web, a good rate would be 10-20 k/sec. For true streaming of video, you need something under 5 k/sec, but your quality will suffer, depending on the source material. Another trick is that you can set the Quality slider down to Low (25) and still get good quality video.

Another nice quality of the Sorenson codec is that it is much more tolerant of higher frame rates than Cinepak is. That is, there is little difference in file size whether your movie's frame rate is 5 fps or 15 fps. You'll have to experiment to see the effects, but in general, you can set your movie's frame rate to be as high as the source material with very little penalty.

The digital artifacts at the end of the Sorenson movie above probably could have been avoided with the Developer Edition of the Sorenson Video codec. The Developer Edition supports Variable Bitrate Encoding, which would have handled the flash of light at the end of the movie more elegantly. Unfortunately, the Developer Edition is rather expensive, so unless you're a serious QuickTime Developer, you're probably best to stick with the Basic Edition included with QT3.

Tips for QDesign Music

QDesign Music is an incredible compressor for music soundtracks. In can take any quality sound sample, even up to 16 bit 44.1 kHz Stereo sound, and compress it down to about 3.0 k/sec or less with very little loss in quality. Because of this, you can leave your sound at the original high quality sample rate and still get a very small but great sounding soundtrack.