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 1920 3 1080), and the number of pixels onscreen is simply the product of these numbers (1920 3 1080 5 2,073,600 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 inten- sity 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 1920 3 1080 resolution with 256 (28) simultaneous colors contains 1920 3 1080 3 1 byte 5 2,073,600 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 4 GBps, 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 720 3 480 and as high as 1920 3 1080. In addition, a single disk drive is attached to the disk controller and has a sustained data transfer rate of 40 MBps when reading sequentially stored data. The channel connecting the disk drive to the disk controller has a data transfer rate of 200 MBps. Finally, the files containing the video frames are uncompressed and stored sequentially on the disk, and copying these files’ contents from the disk to the display controller is the only activity the system performs (no external interrupts, no multitasking, and so forth). The video display controller contains 4 MB of 10 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 10 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 720 3 480?
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 1920 3 1080), and the number of pixels onscreen is
simply the product of these numbers (1920 3 1080 5 2,073,600 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 inten- sity 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 1920 3 1080 resolution with 256 (28)
simultaneous colors contains 1920 3 1080 3 1 byte 5 2,073,600 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 4 GBps, 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 720 3 480 and as high as 1920 3 1080. In
addition, a single disk drive is attached to the disk controller and
has a sustained data transfer rate of 40 MBps when reading
sequentially stored data. The channel connecting the disk drive to the
disk controller has a data transfer rate of 200 MBps.
Finally, the files containing the video frames are uncompressed and
stored sequentially on the disk, and copying these files’ contents
from the disk to the display controller is the only activity the
system performs (no external interrupts, no multitasking, and so
forth). The video display controller contains 4 MB of 10 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 10 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 720 3 480?
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 1200 3 1024?
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 1920 3 1080?
Question 4: How do the answers to Questions 1 to 3 change if the video
files contain compressed images at an average compression ratio of
10:1. Assume that the CPU is fast enough to decompress the files as
they’re read and deliver the uncompressed con- tent to the system bus
at a rate of at least 500 MBps.
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