Computer Graphics: Question Set – 03

What is video adapter?

A video adapter, often known as a video card or graphics card, is a desktop computer plug-in card that does graphics processing. It is also referred to as a display card or a graphics adapter. PCI Express is the interface used by modern display adapters, whereas PCI and AGP were used by older devices.

The maximum resolution supported by the system, the refresh rate, and the amount of colors displayed on the screen are all determined by the video adapter used in the monitor.

No matter how powerful the video adaptor, a monochrome monitor cannot display color.

Nowadays, graphics circuits are incorporated into the motherboard’s chipset, eliminating the need for a separate plug-in card.

There are various graphics adapter cards on the market, such as CGA, VGA, and IBM. Each adapter has a variety of video modes.

graphics card
Powerful modern high end computer graphics card

Discuss the characteristics of video adapter in detail

Video adapter is characterized by following properties:

Maximum Resolution : Resolution is defined as the total number of pixels that can be displayed on a monitor screen without overlapping. It is sometimes represented as the number of dots in the horizontal direction divided by the number of dots in the vertical direction.

A higher resolution allows for a more accurate representation of the scene. The most common resolutions are 640 x 480, 800 x 600, 1024 x 768, and 1280 x 1024. The size of the frame buffer is determined by the screen resolution.

Effect of resolution

Image Source: https://www.insight180.com/the-how-to-guide-of-high-vs-low-resolution/

Color Depth: Color depth is defined as the number of bits needed to represent a color. The size of the frame buffer is also determined by the amount of colors supported by the system.

A system with n bits per pixel can accommodate up to 2n distinct colors. A system with a resolution of 800 x 600 that supports true color (24 bit/pixel) requires (800 x 600 x 24) / (8 x 1024 x 1024) = 1.37 MB memory for the frame buffer.

Demonstration of Color Depth
Demonstration of Color Depth

A system with the same resolution and 256 color support requires (800 x 600 x 8) / (8 x 1024 x 1024) = 0.458 MB memory for the frame buffer.

Refresh rate: The refresh rate determines how many times the screen may be painted in one second. The standard refresh rate in raster CRT monitors and color television sets is 60 Hz. A lower refresh rate may cause flickering.

Multiple resolutions with the same or different colors may be supported by various adapter cards. VGA, for example, supports 640 x 200, 640 x 350, and 640 x 480, with 16 color support in each mode.

graphics card and effect of refresh rate
Effect of refresh rate

Image Source: https://www.techcrackblog.com/2019/06/high-refresh-rate-in-phones.html

TV Tuner: A card with a built-in TV tuner can transform a PC into a television set. We can use a traditional antenna or connect the card to cable or satellite system.

Accelerator: A graphics accelerator is a sort of video adapter that has its own processor to improve performance. Accelerator is in charge of graphics rendering. They are tailored for such tasks and so perform far better than general-purpose CPUs. Because the CPU is not required to render graphics, it may focus on processing other operations.

How much memory is required to retain picture data for one screen if the resolution is 800 x 600 if an RGB display device uses 8 bit per pixel, per color scheme. How much memory is required to keep picture data for one second if the refresh rate is 50Hz?

Total number of pixel = Screen resolution = 800 x 600 = 4, 80, 000 pixels

Each pixel takes 8 bit to represent the color, so total number of bits required to store display information = 4, 80, 000 x 8 = 38, 40, 000 bits

Size of frame buffer in Byte = 38, 40, 000 / 8 = 4, 80, 000 Bytes

Size of frame buffer in KB = 4, 80, 000 / 1024 = 468.75 KB

Size of frame buffer in MB = 468.75 / 1024 = 0.46 MB

To store the picture information of resolution 800 ´ 600 pixels having 8 bit per pixel, 0.46 MB memory is required.

Refresh rate is 50 Hz, so it paints the screen 50 times in a second. On every cycle, new data is loaded in same buffer. So, size of frame buffer do not alter, it is just reloaded 50 times in a second.

Assume that a certain true color system has a resolution of 1200 x 1024 pixels. Determine the system’s frame buffer size.

True color system uses 24 bit / pixel to represent the color.

Total number of pixel = Screen resolution = 1200 x 1024 = 12,28,800 pixels

Each pixel takes 24 bit to represent the color, so total number of bits required to store display information = 12,28,800 x 24 = 2, 94, 91, 200 bits

Size of frame buffer in Byte = 2,94,91,200 / 8 = 36,86,400 Bytes

Size of frame buffer in KB = 36,86,400 / 1024 = 3,600 KB Size of frame buffer in MB = 3,600 / 1024 = 3.5156 MB

Additional Reading: Effect of Refresh Rate


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