Technical reports

Video replay in computer animation

Stuart Philip Hawkins

October 1990, 161 pages

This technical report is based on a dissertation submitted December 1989 by the author for the degree of Doctor of Philosophy to the University of Cambridge, Queens’ College.

DOI: 10.48456/tr-207

Abstract

This dissertation presents a design for an animation system that supports video-rate replay of frame sequences within a frame buffer based graphics architecture.

In recent years framebuffer architectures have become dominant, largely displacing other forms of graphics display system. But a framebuffer representation is not well suited to the support of animation. In particular, two main problems are faced: (1) the generation of each new frame within a single frame time (typically 40ms); and (2) the updating of the framebuffer with the new frame representation, also within one frame time. Both of these problems stem from the fact that the large amount of data required to represent each frame has to be processed within a strictly limited time. The difficulty with updating the frame buffer representation has been largely addressed by the development of powerful new display processor architectures, made possible by developments in semiconductor technology. The generation of frames at replay rates, however, represents a much greater challenge and there are numerous situations for which real time animation is simply inpracticable. In such cases an alternative approach is that of frame-by-frame animation in which the frame sequence is pre-calculated off-line and stored for later replay at the correct speed. This technique is commonly referred to as real-time playback.

In this dissertation the requirements of real-time playback are discussed and a number of distinct approaches to the design of such systems identified. For each approach examples of previous real-time playback systems are examined and their individual shortcomings noted. In light of these observations the design of a new hardware-based animation system is proposed and its implementation described. In this system frames are stored digitally and image compression is used to address the non-video-rate transfer rate and storage capacity limitations of the frame storage device employed (an unmodified 5 1/4 inch magnetic disc drive). Such an approach has previously received little attention. Frame sequences are stored on the disc in a compressed form and during replay are decompressed in real-time using a hardware implementation of the coding algorithm. A variety of image compression strategies are supported within a generalised coding framework. This introduces operational flexibility by allowing the system to be tailored according to the needs of a particular application.

Full text

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BibTeX record

@TechReport{UCAM-CL-TR-207,
  author =	 {Hawkins, Stuart Philip},
  title = 	 {{Video replay in computer animation}},
  year = 	 1990,
  month = 	 oct,
  url = 	 {https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-207.pdf},
  institution =  {University of Cambridge, Computer Laboratory},
  doi = 	 {10.48456/tr-207},
  number = 	 {UCAM-CL-TR-207}
}