Preparing Your Video Loops for Use in ArKaos VJ

ArKaos VJ is a visual sampler, and just as with audio samples, the quality of the samples’ source has an impact on the quality of what the sampler will generate. However, the main difference between audio and video samples is size. While it’s easy to use or play uncompressed audio samples, the large size of video samples makes it nearly impossible to do the same.

If you take a look at the numbers, it won’t take long to figure out that using uncompressed video samples simply requires too much from an average hard drive. An uncompressed full screen video at NTSC resolution (640 x 480) will require approximately 35MB/sec. And of course you’ll want to mix several video loops together, so you’ll need a drive that can read at least 100MB/sec—meaning that you’d need 2GB of disk space to store one minute of uncompressed video!

Hard drives average a data rate of 5 to 30MB/sec. If you try to play a video that demands too much of your system, the video will look jerky, the system will drop frames randomly, and may even freeze—the last thing you want when playing in front of a live audience!

There are two solutions to this problem: scaling and compressing. By scaling the video to 320 x 240, you reduce the data rate of your video to one quarter of the original value. This is the best solution for simultaneous use of multiple video loops.

If you prefer to play your video full screen without resizing, you will need to compress the images. There are a variety of compression methods in existence; the codecs include Sorenson, MPEG, DV, and more. Codecs such as DivX or MPEG 4 have higher quality and compression ratios than others, but require far greater amounts of CPU power to play. Codecs such as Cinepack require less CPU power, but offer decreased quality. The Sorenson and DV codecs seem to achieve the ideal compromise between quality and power requirement. Also, if your hard drive is relatively fast, you can use QuickTime’s animation codec.

In the end, experimentation is the best way to discover which codec is ideal for you and your needs. Play around with an original loop and try to compress it using various codecs. While doing so, enable the display of statistics from the ArKaos VJ menu. This will allow you to see the frame rate as you play each video loop, which will help you determine which compression method is ideal for your system. Once you’ve compressed your video, you’re ready to start the show!