Text sound and images

ASCII code and Unicode

ASCII code

• Text is converted to binary to be processed by a computer according to ASCII code.(8 bits per character)

DEC	OCT	HEX	BIN	Symbol	HTML Number	Description
65	101	41	01000001	A	A	Uppercase A
66	102	42	01000010	B	B	Uppercase B
67	103	43	01000011	C	C	Uppercase C
68	104	44	01000100	D	D	Uppercase D
69	105	45	01000101	E	E	Uppercase E
70	106	46	01000110	F	F	Uppercase F

Unicode

Unicode allows for a greater range of characters and symbols than ASCII, including different languages and emojis. (16 bits per character)

Sound

• A sound wave is sampled for sound to be converted to binary.
• The sample rate is the number of samples taken in a second.
• The sample resolution is the number of bits per sample.

Sample rate

• standard sampling rate is 44 100 samples per second.

Sample resolution

• In audio CDs, each sample is recorded as a 16-bit integer.

Calculating audio file sizes

• The file size = sampling rate x sampling resolution x seconds.

• A 32-second sound clip will be recorded.

• The sound will be sampled 16000 times a seconds.

• Each sample will be stored using 8 bits.

16000 x 8 x 32 = 4096000 bits

Images

• A pixel is a smallest element in a image, its color is represented by three component intensities such as red, green, and blue. (RGB)
• The image resolution is the product of the width multiply with the height of the image.

Colour depth

• Colour depth is the number of bits used to indicate the color of a pixel.
• Normally, we use 24 bits to represent the color of a pixel.
• For example
• #FF 00 00 represents primary colour red
• #00 FF 00 represents primary colour green
• #00 00 FF represents primary colour blue
• #FF 00 FF represents fuchsia

Calculating bit-map image file sizes

• The file size = image resolution x colour depth.

• The image has a resolution of 400 x 300 pixels, and a colour depth of 8 bits per pixel.

400 x 300 x 8 = 960000 bits