Text, sound and images：練習題

In the context of computer science, what is the best definition of a character set?

What is the primary difference between lossy and lossless compression?

A sound engineer records a piece of music. They decide to halve the sample rate while keeping the sample resolution constant. How will this change affect the resulting sound file?

If a digital image has a colour depth of 8 bits, how many unique colours can be represented in that image?

Which statement best describes the relationship between the sample resolution and the quality of a digital sound file?

State one key difference between ASCII and Unicode character sets regarding the number of characters they can represent.

Define the terms resolution and colour depth as they relate to the representation of a digital image.

A stereo sound recording (2 channels) lasts for 10 minutes. The sample rate is 44,100 Hz, and the sample resolution is 16 bits. Calculate the uncompressed file size in Mebibytes (MiB), where \(1 \text{ MiB} = 1024 \times 1024 \text{ bytes}\).

A photographer stores a high-resolution digital image with a resolution of \(4096 \times 2160\) pixels. The image uses a colour depth of 24 bits.

a) Calculate the file size of the uncompressed image in Mebibytes (MiB). Show your working and provide your answer to two decimal places.

b) The photographer decides to use lossless compression to reduce the file size. Describe how lossless compression differs from lossy compression in terms of how the data is reduced and how the file is reconstructed.

c) Identify one method of lossless compression and explain how it could be used to reduce the file size of an image that contains large areas of the same colour.

An image is captured with a resolution of $$1600 \times 900$$ pixels and a colour depth of 16 bits.

a) Calculate the file size of this uncompressed image in Kilobytes (KB). Show your working.

b) Explain how increasing the resolution and colour depth impacts the quality and file size of an image.

c) Data compression methods are often used for images. Describe how lossy compression achieves a smaller file size and state one scenario where it would be appropriate.