Computer Networks · free preview
Multimedia Data and Compression
Multimedia would swamp any network uncompressed, so end-to-end data engineering is largely the art of compression, lossless codes like Huffman assign short bit strings to probable symbols and run-length encoding collapses repeated runs, images split into palette-indexed lossless GIF for graphics and transform-coded JPEG, which blocks the image, takes a discrete cosine transform, quantizes away the high frequencies the eye cannot see, and entropy-codes what remains, while video adds the time axis, MPEG alternating self-contained I frames with P frames predicted from the past and B frames interpolated from both directions via motion vectors, and audio closes the loop with psychoacoustics, MP3 discarding the sounds masking says nobody will hear.
1. Squeezing Without Losing
Squeezing Without Losing
2. Transforming Away What Eyes Miss
Transforming Away What Eyes Miss
3. Borrowing From the Timeline
Borrowing From the Timeline
4. Hearing What Isn't There
Hearing What Isn't There
5. The entropy bargain
What is the essential idea behind Huffman coding?
6. Choosing the image format
A crisp company logo with eight flat colors needs a web format. Why does GIF fit better than JPEG?
7. The lossy step
In JPEG's pipeline, which step actually discards information?
8. Frames that lean
What distinguishes MPEG's B frames from P frames?
9. The cascade
Why does losing one I frame damage more playback than losing one B frame?
10. The psychoacoustic principle
On what principle does MP3 decide what not to encode?
11. The repeated-run trick
What lossless technique replaces a run of repeated symbols with one copy of the symbol and a count?
12. The 8x8 change of basis
Which transform does JPEG apply to each 8x8 block to re-express pixels as spatial frequency coefficients?
13. The moving reference
In MPEG prediction, what does a macroblock's motion vector describe?
14. The hidden sounds
What psychoacoustic phenomenon lets MP3 omit sounds near loud tones?
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