Bit streaming, client-server, peer-to-peer and cloud computing
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Watching before it has finished arriving
- Bit streaming
- Why the video is compressed
Read the transcript of the teaching part
Last time
Before we start: last time, in Vector graphics, character sets and compression, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Watching before it has finished arriving
When you watch a live video call, the picture appears long before the whole call has been sent. The data travels as a continuous stream of bits and is played as it arrives. Who sends it, who asks for it, and where it is stored all depend on the network model. That is today's topic.
Bit streaming
In bit streaming, a file is sent as a continuous stream of bits, and playback starts before the whole file has arrived. On demand streaming sends a stored file when you ask. Real-time streaming sends live events, as they are captured, such as a video conference. The receiver keeps some bits in a buffer so playback stays smooth if the network slows for a moment.
Why the video is compressed
An uncompressed video of 1920 by 1080 pixels, 24 bits per pixel, 30 frames a second, is nearly 1.5 billion bits every second. Few connections can carry that. Compression makes the file smaller, so it needs less bandwidth and arrives faster with fewer pauses. A smaller file is also cheaper to transmit and store.
Chapter 2: Communication
- Bit streaming, client-server, peer-to-peer and cloud computing 6 min
- Ethernet, CSMA/CD, LAN hardware and IP addresses 7 min
- LAN, WAN, topologies and wired and wireless networks 7 min
Also for A Level Computer Science 9618
Which topics come up most in A Level Computer Science 9618 past papers, counted from every paper since 2004: Paper 1 topic frequency, Paper 2 topic frequency.