Lesson 6. Audio and Visual Data Page 14, 15 SBT Informatics 10 Connecting Knowledge to Life>

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6.1

The inverse of the sampling period is called the sampling frequency – which is the number of samplings performed per unit of time (usually seconds).

Choose the wrong combination.

If you want to increase the sound quality, you need

A. increase bit depth.

B. increase the sampling frequency

C. increased sampling period.

D. use good quality sampling equipment.

Solution method:

Increasing the sampling period will reduce the sound quality

Detailed explanation:

If you want to increase the sound quality, you need

C. increased sampling period.

6.2

Question 6.1 introduced the concept of sampling frequency. How is bitrate calculated over bit depth and sampling frequency?

CD music is stereo music with two channels for the right and left speakers, each encoded with a bit depth of 16 bits and a sampling rate of 44.1 KHz each. Please calculate the bit rate of CD music.

Solution method:

Based on the concept of sampling frequency in Question 6.1

Note that many documents still estimate the bitrate of CD music to be 1411 Kb/s. The fact is that 1 KHz is equal to 1000 Hz, and 1 Kb is 1024 b

Detailed explanation:

– Bit depth is the number of bits needed to represent the audio amplitude on the sample bar when sampling. Sampling frequency is the number of samples per second. So bit rate is the number of bits to represent audio per second which is the product of bit depth and frequency.

– The bit rate of CD music is 2 × 44.1 (KHz) × 16 (b) = 1411.2 = 1378 (Kb/s).

6.3

Only the highest quality MP3 music achieves a bit rate of 320Mb/s, CD music has a bit rate about 4 times greater (calculated in Question 6.2). Sophisticated music listeners are often not satisfied with MP3 or CD music but want to use high-resolution sound (Hi-Res Audio). For example, Audio Master music uses a sampling frequency of 192 KHz (audio master) with a bit depth of up to 24 bits.

Please calculate the bit rate of the Audio Master audio format.

How long can a 650MB CD record music in Audio Master format?

Solution method:

Based on the knowledge learned and the data in the question

Detailed explanation:

– Audio Master music bit rate is 192 x 24 = 4500 Kb/s

– With a 650MB or 650 x 1024 KB CD, record music in a writable Audio Master format

650 x 1024 x 8 (bits) / 4500 = 1183 seconds (about 20 minutes)

6.4

Learn MIDI digital music.

How to encode audio using PCM method for all sounds. In music, there are only certain tones whose pitch is determined by certain frequencies. Then PCM encryption will consume storage memory. Musical Instrument Digital Interface (MIDI) was invented.

Let’s learn about MIDI according to the suggestions, what is the MIDI communication standard, what to do, which instruments use MIDI, the benefits of MIDI.

Solution method:

Refer to https://en.wikipedia.org/wiki/MIDI

Detailed explanation:

The MIDI Music Interface Standard is the industry standard for electronic traffic etiquette that defines musical notes in electronic musical instruments as concise and precise synthesizers, for electronic instruments and computers to exchange data. whether, or “say”, to each other

In addition to mobile phones, MIDI is also widely used in electronic instruments such as Keyboard, electric guitar, saxophone…

– MIDI can be thought of as a language and this is the common language that electronic music devices can use to communicate with each other.

6.5

Name some devices that can digitize images.

Solution method:

Image digitization is the conversion of images into bit sequences. The result of digitizing an image is a “digital image”.

Detailed explanation:

Some devices can digitize photos

– Digital cameras.

– Scanner (scanner).

– Digital camera video.

The device uses drawing software on the touch screen called a digitizer.

– A phone or tablet with a touch screen can be used as a photo digitizer.

6.6

What does the bit depth of an image represent?

A. The size of the image.

B. The detail of image components when displayed.

C. Color subtlety of the image.

D. Image fidelity.

Solution method:

Bit depth represents the color subtlety of an image

Detailed explanation:

The bit depth of the image represents:

C. Color subtlety of the image.

6.7

Image resolution (resolution) is measured in units of dpi (dot per inch) which is the number of pixels per inch (1 inch equals 2.54 cm) of the display device (such as a monitor or printer). Does resolution have anything to do with image encoding? Is it a measure of image quality?

Solution method:

Applying self-knowledge

Detailed explanation:

Resolution is just a feature of the display device, has nothing to do with the digitization of the image and its quality.

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