Assignment

A video frame displayed onscreen consists of many pixels, with each pixel, or cell, representing one unit of video output. A video display s resolution is typically specified in horizontal and vertical pixels (such as 800 600), and the number of pixels onscreen is simply the product of these numbers (800 600 480,000 pixels). A pixel s data content is one or more unsigned integers. For a black-and-white display, each pixel is a single number (usually between 0 and 255) representing the intensity of the color white. Color pixel data is typically represented as one or three unsigned integers. When three numbers are used, the numbers are usually between 0 and 255, and each number represents the intensity of a primary color (red, green, or blue). When a single number is used, it represents a predefined color selected from a table (palette) of colors.

Motion video is displayed onscreen by copying frames rapidly to the video display controller. Because video images or frames require many bytes of storage, they re usually copied to the display controller directly from secondary storage. Each video frame is an entire picture, and its data content, measured in bytes, depends on the resolution at which the image is displayed and the maximum number of simultaneous colors that can be contained in the sequence of frames. For example, a single frame at 800 600 resolution with 256 (28 ) simultaneous colors contains 800 600 1 byte 480,000 bytes of data. Realistic motion video requires copying and displaying a minimum of 20 frames per second; 24 or 30 frames per second are common professional standards. Using fewer frames per second results in a jerky motion because the frames aren t being displayed quickly enough to fool the eye and brain into thinking that they re one continuously changing image. Assume the computer system being studied contains a bus mastering disk controller and a video controller that copies data to the video display at least as fast as it can be delivered over the bus.

Further, the system bus can transfer data at a sustained rate of 100 Mbps, as can both the controllers bus interfaces. This system will be used to display motion video on a monitor capable of resolutions as low as 640 480 and as high as 1024 768. In addition, a single disk drive is attached to the disk controller and has a sustained data transfer rate of 20 MB per second when reading sequentially stored data. The channel connecting the disk drive to the disk controller has a data transfer rate of 80 Mbps. Finally, the files containing the video frames are stored sequentially on the disk, and copying these files contents from disk to the display controller is the only activity the system will perform (no external interrupts, no multitasking, and so forth).

The video display controller contains 2 MB of 50 ns, 8-bit buffer RAM, and the video image arriving from the bus can be written to the buffer at a rate of 8 bits per 50 ns. The video display s RAM buffer can be written from the bus while it s being read by the display device (sometimes called dual-porting ). Finally, data can be received and displayed by the display device as fast as the video controller can read it from the RAM buffer.

Question 1. What is the maximum number of frames per second (round down to a whole number) that this system can display in 256 simultaneous colors at a resolution of 640 480?

Question 2. What is the maximum number of frames per second (round down to a whole number) that this system can display in 65,536 simultaneous colors at a resolution of 800 600?

Question 3. What is the maximum number of frames per second (round down to a whole number) that this system can display in 16,777,216 simultaneous colors at a resolution of 1024 768?