---
title: "Need for data compression"
subject: "Multimedia System"
chapter: 5
key: "semester_8/multimedia_system:need-for-data-compression"
source: https://www.bctengineer.com/q/semester_8/multimedia_system/need-for-data-compression
site: BCT Engineering
---

# Need for data compression

Multimedia System · Chapter 5: Data Compression

- Asked in: 2074 Magh, 4 marks
- Video: [Data Compression as Fast As Possible](https://www.youtube.com/watch?v=guo8if4Yxhw) — Techquickie
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/multimedia_system/need-for-data-compression
- Whole chapter: https://www.bctengineer.com/md/semester_8/multimedia_system/chapter-5

## Question

Why do we need data compression?

## Short answer

Multimedia data is very large while storage and bandwidth are limited. Compression reduces bits for faster transmission, lower cost, real-time streaming, and more storage. It works by removing redundancy and details humans cannot perceive.

## Answer

Multimedia data (audio, image, video) is very large, while storage capacity and network bandwidth are limited. Data compression reduces the number of bits needed, so such data can be stored and sent practically.

**Reasons**
1. **Large data volume.** Uncompressed CD-quality stereo audio needs 44,100 x 16 x 2 = 1.41 Mbps. A 1024 x 768 true colour image is 1024 x 768 x 3 bytes = 2.36 MB. Uncompressed video at 640 x 480, 24 bit, 25 fps needs about 184 Mbps (23 MB/s).
2. **Limited storage.** A CD (about 700 MB) would hold only about half a minute of such video without compression.
3. **Limited bandwidth.** A typical home connection or mobile network cannot carry raw video in real time.
4. **Faster transmission and lower cost.** Smaller files download and upload faster and use less data.
5. **Real-time delivery.** Video conferencing, streaming and broadcasting need data rates that fit the channel.
6. **Efficient use of devices.** Mobile phones and cameras can store more photos and videos.

**Why it works:** media contains redundancy (neighbouring pixels are alike, successive video frames are similar) and irrelevance (details humans cannot see or hear). Compression removes both.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the main reason compression is needed for multimedia?
   A. Multimedia data is very large while storage and bandwidth are limited
   B. Multimedia data is too small to store
   C. Compression makes images more colourful
   D. Networks are too fast to carry small files
   Answer: A. Audio, image and video are huge, so fewer bits are needed to store and send them practically. (Key point: Core reason)

2. What is the size of an uncompressed 1024 x 768 true-colour image?
   A. About 0.8 MB
   B. About 2.36 MB
   C. About 7 MB
   D. About 24 MB
   Answer: B. 1024 x 768 x 3 bytes is about 2.36 MB. (Key point: Data volume calculation)

3. Why is it possible to compress media?
   A. Media contains no information
   B. Media is always random
   C. Media has redundancy (similar neighbouring pixels, similar frames) and irrelevance (details humans cannot perceive)
   D. Humans can perceive all details
   Answer: C. Compression removes redundancy and irrelevance. (Key point: Why compression works)

## Related in Multimedia System

- [Data compression techniques](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Adata-compression-techniques) — Multimedia System, chapter 5, asked 2×
- [Lossless versus lossy compression](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Alossy-vs-lossless) — Multimedia System, chapter 5
- [Why lossy compression is preferred](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Awhy-lossy-preferred) — Multimedia System, chapter 5

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- [Why do we need FFT](https://www.bctengineer.com/question.md?key=semester_7%2Fdigital_signal_analysis_and_processing%3Awhy-need-fft) — Digital Signal Analysis and Processing, chapter 7, asked 2×
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