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Your smartphone has a display resolution of 720 times 1280 pixels, and each pixe

ID: 3814882 • Letter: Y

Question

Your smartphone has a display resolution of 720 times 1280 pixels, and each pixel is composed of three colors (blue, green and red) and each color is expressed by 8 bits. In order to display visual contents smoothly, each picture frame should be refreshed 30 times per second. How many bits of image data should be delivered to your smartphone per second to see smooth video stream at its full resolution if no data compression process is used? In order to fit this into the maximum transmission speed of4G LTE, which is ~ 100 Mbps, what is the minimum data compression ratio needed here?

Explanation / Answer

Resolution = 720x1280 pixels.

Frame size = 720 * 1280 = 921600 pixels.

Each pixel has R,G,B each color is 8 bits, i.e., each pixel has 24 bits.

No of frame bits = 921600 * 24 = 22118400 bits

Refresh rate = 30 times per second.

Therefore, if no data compression is used, no. of image bits required are

22118400 * 30 = 663552000 bits per second i.e., UNCOMPRESSED DATA RATE = 663552000 bps

Maximum 4G transmission speed = 100 Mbps i.e., COMPRESSED DATA RATE = 100Mbps

MINIMUM COMPRESSION RATIO = (UNCOMPRESSED DATA RATE / COMPRESSED DATA RATE)

= 663552000 / (100 * 1024 * 1024) (converting Mbps to bps)

= 663552000 / 104857600

= 6.328125

= 632.8125%