DVI Galactic Challenge Demo

    by Douglas Dixon

The Galactic Challenge interactive concept demonstration developed at Sarnoff in 1984 included many seminal ideas which were to become key concepts in DVI Technology and future multimedia applications, including:

    - Compressed motion video at PC data rates
    - Interactive control of motion through environment
    - 360-degree panoramas seamed from still photos
    - Animated overlays of objects and motion video

	Introduction		Video Compression
	Storyline		Panoramic Pyramid Seaming

Introduction

The Galactic Challenge sample application was developed in 1984 to demonstrate the flexibility of digital video, especially as a medium for interactive exploration, with interactive control of motion sequences and pans. The user should also be able to interact with characters provided as foreground objects overlaid on the background motion video frames. The addition of digitized audio could also make the experience even more convincing and realistic.

We christened our application Galactic Challenge in a fit of modesty, and invented a science fiction story about a spacecraft that explores an alien landscape and fights off attackers, only to be detected and captured by a huge base ship in the climactic finale. In early 1984 this concept was developed into a demonstration videotape, including one component which was also developed into an interactive demonstration.

Galactic Challenge was implemented in March 1984 as an interactive application program on the host VAX system, using two Ikonas graphics systems for the background video and foreground objects. User input came from a serial joystick attached to the VAX, and the audio was generated from a custom audio board also connected to the VAX by a serial line.

Creating Galactic Challenge required a large team effort, including design and development of the application, production of the video and audio sequences, construction of the spaceship models, implementation of the audio hardware, and development of the controlling software. 

But the hardest part of the project was simply the logistics of preparing all the material, especially because the video and audio sequences needed to be compressed and then re-expanded to appear as they would in the product. For example, The overlay object sequences, including the princess, enemy spacecraft, laser fire, and explosion, were manually digitized from over 200 frames. They were then edited to remove the background so the objects could be digitally overlaid on the video.

The resulting interactive demonstration and videotape were very successful, and served the purpose of conveying the DVI concept to RCA management. In particular, the interactive demonstration which allowed users to use the joystick to pan around the open field and try to shoot down enemy spacecraft was very effective in communicating the interactive video experience, in comparison to existing personal computer games with graphics-only displays. Over the next few months Galactic Challenge demonstrations were presented at the rate of at least one a week to corporate and division management, who we were trying to convince of the importance of bringing DVI to product quickly. The interactive demonstrations continued into early 1985, until new demonstrations based on the final product hardware design had been developed, and the videotape was still being used in mid-1986.

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Storyline

Overlooking the Lake

The final videotape begins with an overhead view of the Emperor's Gardens and a narrated introduction. We start the action by traveling down a wooded road, and then turn left to pan over a lake. An enemy spacecraft swoops down to attack, we fire back, but the enemy escapes to warn its base ship.

Princess Appears at the Fork in the Path

We then turn back onto the path, and continue to a fork in the road. We stop and pan around to try to determine which direction to go. Suddenly, a magic princess appears in the road and advises us to turn left.

Final Battle Action at the Field

We then proceed out of the woods into a large, open field. Once again we stop and look around. We turn in a full circle, looking up and down over the entire scene. Another enemy craft appears and attacks, we fire back, and it explodes into a ball of flame. But it is too late, for the base ship has caught us, and we are lifted up by a tractor beam to an unknown fate.

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Video Compression

All the video sequences in the Galactic Challenge were compressed using a YIQ pyramid compression algorithm so that the video quality on the videotape would be representative of the quality which could be provided by a consumer product.

  Pyramid representation  YIQ color space quantization

Over 900 frames of the motion sequences were digitized by hand, frame by frame, with one person stepping the videotape machine, and a second running the Ikonas to digitize and save each image. 

The sequences were then processed by overnight batch jobs on the VAX to compress the frames and then decompress them to be ready for display. After suffering through this tedious manual operation, we soon expanded the Ikonas with an attached CPU and hard disk to automate the digitizing process.

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Panoramic Pyramid Seaming

The videotape included several opportunities to stop and pan the view over the scene, at the lake, at the fork in the road, and at the final battle in the field. The field panorama was a full 360 degree circle, stitched together from still photos shot around in a circle.

The panorama at the field was digitized from individual overlapping images shot in a 360 degree circle, manually aligned, and then seamed together using the pyramid seaming technique.

Final seamed 360-degree panorama at the field

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