File Format Comparison (SQA National 5 Computing Science): Revision Note
Exam code: X816 75
WAV and MP3 (Audio)
What are WAV and MP3?
WAV and MP3 are standard audio file formats used on websites
They store sound differently which affects:
Quality
File size
WAV
Aspect | Explanation |
|---|---|
Compression | No compression is applied, no data removed |
Type | Lossless |
Quality | Full quality, identical to original |
File size | Very large because all samples are stored |
Good for editing and archiving, inefficient for websites
MP3
Aspect | Explanation |
|---|---|
Compression | Lossy compression removes data permanently |
Type | Lossy |
Quality | Reduced compared to original audio |
File size | Much smaller due to data removal |
Ideal for fast loading and streaming
Summary
Format | Compression | Quality | File Size |
|---|---|---|---|
WAV | Uncompressed, lossless | High | Large |
MP3 | Lossy compression | Lower | Small |
JPEG, GIF and PNG (Graphics)
What are JPEG, GIF, and PNG?
JPEG, GIF, and PNG are standard bit-mapped graphic formats used on websites
You must compare them in terms of:
Animation
Transparency
Animation
Animation in graphics means displaying a sequence of images (frames) one after another to create the appearance of movement
The graphic format stores multiple frames inside a single file
GIF supports animation
Used for simple moving graphics like loading icons or short looping images
Transparency
Transparency means parts of an image can be see-through
Transparent pixels allow the background of the webpage to show through
GIF supports 1-bit transparency (a pixel is either fully visible or fully invisible)
PNG supports alpha transparency, meaning each pixel can have different transparency levels, creating smooth edges
JPEG does not support transparency
JPEG
Aspect | Explanation |
|---|---|
Compression | Lossy compression removes data permanently |
Type | Lossy |
Colour depth | Millions of colours (24-bit) |
Transparency | Not supported |
Animation | Not supported |
File size | Smaller than PNG, larger than GIF when comparing simple images |
Notes | Best for photographs and detailed images where high colour depth matters |
GIF
Aspect | Explanation |
|---|---|
Compression | Lossless compression |
Type | Lossless |
Colour depth | 256 colours (8-bit) |
Transparency | 1-bit transparency (on or off) |
Animation | Supported (GIF animations) |
File size | Very small due to limited colours |
Notes | Best for simple graphics, logos, diagrams, and animations |
PNG
Aspect | Explanation |
|---|---|
Compression | Lossless compression |
Type | Lossless |
Colour depth | Millions of colours (24-bit or 32-bit with transparency) |
Transparency | Full alpha transparency (smooth edges) |
Animation | Not supported in standard PNG |
File size | Larger than JPEG and GIF |
Notes | Best for images needing high quality and clean transparency, such as UI elements |
Summary
Feature | JPEG | GIF | PNG |
|---|---|---|---|
Compression | Lossy | Lossless | Lossless |
Animation | No | Yes | No |
Transparency | No | Yes (1-bit) | Yes (alpha channel) |
Colour depth | Millions of colours | 256 colours | Millions of colours |
File size | Small | Very small | Medium |
Best for | Photos | Simple graphics, logos, animations | High-quality images needing transparency |
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