---
title: "Why lossy compression is preferred"
subject: "Multimedia System"
chapter: 5
key: "semester_8/multimedia_system:why-lossy-preferred"
source: https://www.bctengineer.com/q/semester_8/multimedia_system/why-lossy-preferred
site: BCT Engineering
---

# Why lossy compression is preferred

Multimedia System · Chapter 5: Data Compression

- Asked in: 2074 Bhadra, 4 marks
- Video: [Data Compression Techniques | Lossy | Lossless | CG | Computer Graphics | Lec-65 | Bhanu Priya](https://www.youtube.com/watch?v=M4lqL9_D2FM) — Education 4u
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/multimedia_system/why-lossy-preferred
- Whole chapter: https://www.bctengineer.com/md/semester_8/multimedia_system/chapter-5

## Question

Explain why lossy data compression is sometimes preferred over lossless. Justify.

## Short answer

Lossy compression is preferred for multimedia because human eyes and ears cannot detect every detail, so removing that detail gives much smaller files with little visible quality loss. It enables streaming and storage with limited bandwidth, offers adjustable quality, and supports real-time use. Lossless remains for text, code, and medical images.

## Answer

Lossy compression is sometimes preferred because multimedia data is meant for human eyes and ears, which cannot detect every detail. Removing the undetectable detail gives much smaller data with little visible loss in quality.

**Justification**
1. **Much higher compression.** Lossless methods give about 2:1 for photos; JPEG gives 10:1 to 20:1 with good quality, and MPEG gives 50:1 or more for video. Raw video at about 184 Mbps would be impossible to stream or store without it.
2. **Limited bandwidth and storage.** Internet streaming, mobile networks, video calls and digital TV need data rates that only lossy coding can reach.
3. **Human perception limits.** The eye is less sensitive to colour than brightness and to fine high-frequency detail; the ear cannot hear sounds masked by louder ones. These parts can be removed unnoticed.
4. **Adjustable quality.** The user can trade quality for size (for example, the JPEG quality factor or MP3 bit rate).
5. **Real-time use.** Faster transmission makes live conferencing and broadcasting practical.

**Example:** a 5 MB photo saved as JPEG at 85% quality may be 500 KB, and viewers see almost no difference.

Lossless compression is still preferred for text, code and medical images where exactness is vital.

## Check yourself

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

1. What makes lossy compression acceptable for multimedia?
   A. Humans cannot detect every detail, so undetectable detail can be removed
   B. Computers cannot store exact data
   C. All details are visible to humans
   D. It keeps every bit
   Answer: A. Eye is less sensitive to colour and fine detail; ear misses masked sounds. Removing these is unnoticed. (Key point: Perception limits)

2. Which is correct about ratios?
   A. Lossless gives 50:1 on video
   B. Lossless gives about 2:1 for photos; JPEG gives 10:1 to 20:1 and MPEG 50:1 or more
   C. JPEG gives 2:1 and lossless 20:1
   D. All methods give 2:1
   Answer: B. Much higher ratios make streaming and storage practical. (Key point: Compression ratios)

3. What benefit does the JPEG quality factor or MP3 bit rate show?
   A. Quality is fixed
   B. The user can trade quality for size
   C. Files cannot be changed
   D. It makes compression lossless
   Answer: B. Lossy coding allows adjustable quality versus size. (Key point: Adjustable quality)

## Related in Multimedia System

- [Lossless versus lossy compression](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Alossy-vs-lossless) — Multimedia System, chapter 5
- [Meaning of lossy compression](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Alossy-compression-meaning) — Multimedia System, chapter 5
- [Data compression techniques](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Adata-compression-techniques) — Multimedia System, chapter 5, asked 2×
- [Need for data compression](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Aneed-for-data-compression) — Multimedia System, chapter 5

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