Lesson video

Hello, I'm Dr.

Das.

Welcome to Computing.

I'm so pleased that you have decided to join me for the lesson today.

In today's lesson, we will be looking at the need for data compression.

Welcome to today's lesson from the unit Data Compression.

This lesson is called the Need for Compression.

And by the end of today's lesson, you will be able to describe why data compression is used and explain its advantages.

Some of the keywords that we will be using in the lesson today are compression.

Compression, the process of reducing file size.

Bandwidth.

Bandwidth, the maximum amount of data that can be transferred over a communication channel.

Latency.

Latency, the time delay between a signal being sent and a signal being received.

This lesson is divided into two sections.

In the first section, we will be looking at describing data compression.

In the second section, we will be looking at explaining the advantages of data compression.

Let's start with the first section, where we'll learn how to describe data compression.

Lucas wants to share an audio file with Jun, who lives in a different town.

The audio file is 25 MB.

Lucas says, "I've tried to email the audio file to you Jun, but the audio file is too large! The computer says the maximum attachment size is 20 MB." June says, "Maybe there's another way you could share the file with me.

I'd really like to listen to your song." How would you share the audio file with Jun? One way to share the file would be to save it to a memory stick.

Lucas says, "I could save the audio file on a memory stick and post it to you in the mail." Jun says, "It might take days for the memory stick to arrive though, and I'd have to send it back to you afterwards.

There must be another way?" Compression is used to reduce the size of files.

Lucas says, "I've compressed the song to reduce the file size.

It's only 2.

5 MB now.

I've just sent you the email." Jun says, "That's great.

Thanks, Lucas.

The email has arrived already.

That was quick! Your song sounds great." A compressed file takes up less storage space and can be shared more easily over the internet.

Data compression is the process of reducing the size of a file.

To compress a file, compression algorithms are used.

Data compression algorithms work by removing unnecessary data or rearranging information more efficiently.

Image files can be compressed.

Image files, like the one shown on the slide, can be compressed.

Image files contain data that a computer uses to represent pictures and images.

They store information about pixels, colours and metadata, which allows computers to display and edit images.

The file size of a typical photo on a modern camera can vary, but is usually between 10 MB and 25 MB.

Common uncompressed file formats for images are BMP and RAW, R-A-W.

One commonly used compression for images is JPEG, J-P-E-G, JPEG.

By compressing the original BMP file into a JPEG format, the file size of this image, as you can see here, has reduced from 10 MB to 1 MB.

That's a huge reduction.

The compressed file is 10 times smaller than the BMB.

Even so, it can be difficult to see the difference between uncompressed and compressed images.

Can you see the difference? There are many types of compression.

Each is suited to specific types of data or applications.

Let's have a quick look at these.

A JPEG format is ideal for compressing photos and digital images.

An MP3 is designed to compress audio files like music and podcasts.

MP4 is commonly used to compress videos like movies.

And a ZIP file is used to compress multiple file types into one smaller file.

Using the right compression method for a file helps maintain the right balance of quality and size and ensures that the data works properly after being compressed.

Note that the aim of all compression algorithms is to reduce the number of bits of data needed to represent the same information.

Let's do a quick check before we move on.

Which of the following is most suited to compress audio files? Why don't you pause the video here and have a quick think? Did you choose option C, MP3? Well done.

Another check.

Data compression is the process of increasing the size of a file.

What do you think? Is the statement true or false? Pause the video here and have a quick think.

You're right, the answer is false.

Why? Because data compression is the process of reducing the size of a file, not increasing.

Well done on getting that one right.

That brings us to the end of this section.

Before we move on, why don't you just do this quick task to make sure that you have understood what we covered in this section.

Task A is split into two parts.

The first part asks you to match the file type to the most suitable compression format.

Why don't you pause the video here and try and work this out? I'm sure you'll be able to.

Right, let's have a look.

To compress an audio file, you use the MP3 format.

To compress a video file, you use the MP4 format.

To compress an image file, you use the JPEG format.

And finally, to combine multiple files into a single smaller file, you use the ZIP format.

Well done.

Let's look at the next part.

Write a paragraph to describe data compression in your own words.

Pause the video here and try and work this out.

Okay, let's look at what the description is.

As we have seen, data compression is about reducing the size of a file.

There are different data compression algorithms that can be used to reduce the size of different file types like images and audio.

Data compression algorithms work by removing unnecessary data or rearranging information more efficiently.

Well done on working that one out.

You're doing brilliantly.

Let's move on.

That brings us to the next section, where we will look at explaining the advantages of data compression.

There are a number of advantages to using data compression, such as a reduction in the space needed to store files locally and in the cloud, less bandwidth usage when transferring data on a network, and faster uploading and downloading times to reduce latency.

Files such as documents, images, video and audio all need to be stored either locally or in cloud storage.

By using compression to reduce the size of files, you can fit more files in the same storage capacity.

This means that local and cloud-based storage costs can be reduced and files can be stored more efficiently.

Jun says, "I have taken some holiday photos that I need to store.

They were taken by a professional photographer and are in BMP format.

They're 32 GB in total, but I only have 10 GB of cloud storage left." Hmm, what could Jun do? Jun could use data compression to reduce the size of the files from 32 GB to 3.

2 GB or less.

This means that Jun wouldn't have to purchase the extra storage from the cloud service and his data would be stored more efficiently.

Bandwidth is about the maximum amount of data that can be transferred over a communication channel at one time.

Bandwidth is usually measured in bits per second.

Many modern home internet providers have bandwidth in the range of Mbps or even Gbps, so megabits per second or gigabits per second.

Lucas says, "So bandwidth is measured in bps.

Is that bytes per second?" Jun says, "No, bandwidth is usually measured in bits per second, but we could convert it into bytes per second." How? You can convert bits into bytes using the fact that there are eight bits in a byte.

So bytes would be the total number of bits divided by the number of bits in a byte.

So if you wanted to convert 100 megabits into its equivalent number of bytes, we would do 100 Mb divided by 8, or 100 million bits divided by 8, which gives us 12.

5 MB, here note the B is the uppercase B, which denotes bytes, so 12.

5 megabytes or 12,500,000 bytes.

A 100 Mbps network, so 100 megabits per second network, can transfer data at an approximate rate of 12.

5 megabytes per second.

12.

5 M uppercase Bps.

Because a compressed file contains fewer bits of data, less bandwidth is needed to transfer the file across the network.

This has a number of advantages, such as reducing network load and faster data transfer.

By reducing load on the network, you can leave more space for other data to be transferred.

This means that there will be more bandwidth available for other devices to use the network more effectively.

Lucas says, "We have lots of devices connected to our home network.

Extra bandwidth will help make sure everyone can use their devices reliably without them slowing down too much." Right, let's do a quick check.

Bandwidth is usually measured in bytes per second.

What do you think? Is the statement true or false? Why don't you pause the video here and have a quick think.

You've been doing so well, I'm sure you'll be able to work this one out.

You're right, the answer is false because bandwidth is usually measured in bits per second, not bytes per second.

Another check.

Compressing files before storing usually (pauses).

What does it do? You've been given three options, pause the video here and try and work this out.

Well done, the option is B, it decreases costs and increases storage efficiency.

That's brilliant.

You've done such a wonderful job up to now.

Let's move on.

Jun says, "I've noticed sometimes that my music player stops playing and says buffering.

What does that mean?" Buffering happens when video, audio or other file pauses so that more data can be loaded.

A number of factors can cause buffering.

It can be a sign of high latency.

Latency is about the delay between sending and receiving data over a network.

Latency is measured in milliseconds, so small m, small s, milliseconds.

Lucas says, "Sometimes when I play a video game, I press a button and there's a delay until something happens on the screen.

I normally say the game is lagging." Lag is the noticeable delay or stuttering effect caused by high latency.

When latency is high, you might notice slow response times with buffering videos and audio and lag in online games.

When latency is low, you should get smooth streaming of audio and video, fast webpage loading, and lag-free games.

An advantage of using data compression is that it can reduce latency.

This is because data compression reduces the size of files and smaller files can be transferred across a network in less time.

Note that there's always some latency when transferring data over a network, but it should be reduced as much as possible to improve the user experience.

To reduce latency and save bandwidth, video and streaming services compress that content using MP3 and MP4 file formats.

Data compression helps streaming services provide a smooth user experience across a range of devices.

Right, let's do a quick check.

So what is latency? Latency is about (pauses).

You've been given three options here.

Is it about reducing the size of a file? Is it about the delay between sending and receiving data? Or is it about storing files efficiently? Why don't you pause the video here and have a quick think.

Did you choose option B? You're right.

Latency is about the delay in sending and receiving data.

Well done.

This brings us to the end of this section.

Just to make sure that you have understood what we've covered in this section, why don't you attempt this task? Task B is made up of two parts.

The first part asks you to explain two possible advantages of using data compression.

Jun says, "I've built a new webpage about sports for a school project.

It has some text, a video in MP4 format, and several images that are in BMP format.

It seems to take a long time to load even though the video is MP4." The second part of task B asks you to write a few sentences to suggest how Jun might be able to reduce the load time of his website using data compression.

Pause the video here and try and work these two parts out.

You're doing so well, I'm sure you'll be able to.

Okay, let's look at the two parts for task B.

The first exercise asked you to explain two possible advantages of using data compression.

The first advantage is that data compression can be used to reduce file sites.

This means that files take up less space on devices like hard drives and USBs and on cloud storage.

An example of this could be a compressed JPEG image, which is much smaller than a BMP image, allowing more pictures to be stored.

The second advantage of data compression is that it can make data transfer faster and can improve streaming.

For example, an MP3 music file would load much faster than an uncompressed WAV file.

This would help music streaming smoother and reduce buffering.

Well done.

Let's look at part two.

So we were trying to solve Jun's problem.

Jun could make his website load faster by reducing the size of his image files.

Right now, his BMP images will take longer to load on the page because they aren't compressed.

If he uses data compression and a file type such as JPEG, they might be 10 times smaller and load much faster on the webpage.

It will be difficult for the viewers of his webpage to see any differences in quality between the JPEG and BMP images.

Jun says, "Oh yes, I forgot to compress the images.

That's a great suggestion, I'll compress them into JPEG format." There, you've solved Jun's problem.

Well done.

That brings us to the end of today's lesson.

Let's quickly summarise what we have covered in this lesson.

We looked at the need for compression.

Compression is used to reduce the size of files.

Different compression algorithms are suited to different file formats, such as images, videos, audio, and documents.

Compression reduces file size, which helps save bandwidth when transmitting data.

Reducing the file size through compression also helps speed up data transmission by reducing latency.