11 - ICT: SOUIND AND VIDEO EDITING

 1. Find out what the resolution is for 4K.

3840 × 2160 pixels (or 4096 × 2160 in the movie industry).

2. Find out why black bars are sometimes added to the top or sides of a video

Black bars are sometimes added to make a video the correct aspect ratio for the screen. If the video is a different aspect ratio to the screen, the black bars will fill the empty parts of the screen.

3. Find out which video file formats are suitable for the web. 

Formats could include: 

 • MP4 

 • MOV 

 • AVI 

 • FLV. 

4. Find out whether the file formats for the web use lossy or lossless compression.

Compression methods are: 

• MP4 – lossy 

• MOV – lossy 

• AVI – can be both 

• FLV – lossy

5 a Calculate the size of a file in megabytes (MB) that is two minutes in length, has a sample rate of 44.1 kHz and a sample resolution of 16-bit. 

To calculate the size of an uncompressed audio file (like a WAV file), we use the following formula:

$$\text{File Size (bytes)}=\text{Sample Rate (Hz)}\times \text{Bit Depth (bits)}\times \text{Channels}\times \text{Duration (seconds)}$$

I'll assume stereo (2 channels), which is standard for most audio files.

Given:

• Duration: 2 minutes = 120 seconds

• Sample Rate: 44.1 kHz = 44,100 samples per second

• Bit Depth (Sample Resolution): 16 bits per sample

• Channels: 2 (stereo)

Step 1: Calculate File Size in Bits

$$\text{Size (bits)}=44,100\text{Hz}\times 16\text{bits}\times 2\text{channels}\times 120\text{seconds}$$$$=44,100\times 16\times 2\times 120$$$$=169,344,000\text{bits}$$

Step 2: Convert to Bytes (1 Byte = 8 Bits)

$$\text{Size (bytes)}=\frac{169,344,000}{8}=21,168,000\text{bytes}$$

Step 3: Convert to Megabytes (1 MB = 1,048,576 Bytes)

$$\text{Size (MB)}=\frac{21,168,000}{1,048,576}\approx 20.19\text{MB}$$

Final Answer:

A 2-minute stereo audio file with a 44.1 kHz sample rate and 16-bit resolution is approximately 20.19 MB in uncompressed (WAV) format.

• • If you meant binary megabytes (MiB), the answer is 10.09 MB.

• If you meant decimal megabytes (MB), the answer is 10.58 MB.

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 b Compare the file size if the sample resolution is increased to 32-bits. As size is an important factor when streaming or downloading music, sound files are often compressed.

It increases to 21.17 MB, so it doubles in size.

EXAM-STYLE QUESTIONS 

 1 Define what is meant by the aspect ratio of a video. [1] 

The proportion of a screen or video width to its height

 2 State why a trimming tool would be used on a video clip. [1] 

One from the following [1]: 

 • The video clip may be too long. 

 • To remove part of the video clip.

 3 Explain two advantages of using captions on a video clip. [2] 

Both of the following [2]: 

 • They can be used to provide further information about the image or video shown. 

 • They can be used to provide further information about where a user can learn more about the context of the image or video.

 4 Explain two advantages of using a lossy compression method on a video file. [2] 

Both of the following [2]: 

 • It makes the video file smaller, so it is quicker to download / stream. 

 • It makes the video file smaller to it takes less storage space.

 5 Explain one disadvantage of using a lossless compression method on a sound file. [1] 

It will not reduce the file size as much as lossy, so it will take up more storage space [1].

 6 Explain what is meant by the sample rate of a sound file and how it affects the file size. [2]

Both of the following [2]: 

 • The sample rate is the number of times sound is sampled in a second. 

 • If the sample rate is increased, it will increase the overall size of the file