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Theory Notes/🌐 Topic 2: Internet & Communication Technologies/11.2.3
11.2.3Grade 11

Transmission of Data Over the Internet

Multimedia over the Internet — how downloading differs from streaming, and how compression makes both possible.

Download
The entire file is transferred to and saved on the local device before it can be used/played.
Streaming
Media is played back as it arrives, without saving the complete file first — requires a consistent, sufficient bandwidth to avoid buffering.

Effect on bandwidth: streaming requires continuous, sustained bandwidth for the duration of playback; a slow or inconsistent connection causes buffering. Downloading can use available bandwidth in bursts and doesn't need to be continuous.

  • Video on-demand — pre-recorded video content streamed whenever the user chooses (e.g. Netflix).
  • VOIP (Voice Over IP) — voice calls transmitted as data over the Internet rather than a traditional phone network.
  • Podcast/Vodcast — episodic audio (podcast) or video (vodcast) content, typically downloaded or streamed on demand.

Compression technology reduces file size for faster transmission/storage:

TypeHow it worksTrade-off
LosslessCompresses data without discarding any information — original can be perfectly reconstructedLarger file size than lossy for the same content
LossyDiscards some data judged less noticeable to save more space (common for sound/image/video)Smaller file size, but some quality is permanently lost

Lossy compression of sound files (e.g. MP3) removes audio frequencies/details less perceptible to the human ear to significantly reduce file size while keeping acceptable quality.

There is always a trade-off between compression quality and bandwidth/speed: higher quality (less compression) means larger files needing more bandwidth and time to transmit; more compression means faster transmission but lower quality.

💡 Exam Tip

If asked to justify lossy vs lossless for a scenario: use lossless for anything where accuracy is critical (e.g. medical images, software files); use lossy where some quality loss is acceptable in exchange for much smaller size (e.g. streaming music).