Multiple choiceQuestion 1 · Recall
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By the end you can explain bit streaming and buffering, compare real-time and on-demand streaming, and calculate how much data a stream uses and when a buffer runs dry.
When you press play on a two-hour film, it starts in seconds. The film isn't on your device yet; it's arriving while you watch, a few seconds ahead of the bit you're seeing.
That's bit streaming. And those few seconds of head start live in the buffer.
Bit streaming
Sending data such as video or audio as a continuous sequence of bits over a network, so it can be played as it arrives without waiting for the whole file to download.
Buffer
An area of memory that temporarily holds data that has arrived but hasn't been played yet. Playback starts once enough data is buffered, which smooths out changes in the download speed.
| Real-time (live) | On-demand | |
|---|---|---|
| What is streamed | an event as it happens: a match, a concert, a video call | pre-recorded files stored on a server |
| When you watch | at the same time as everyone else (with a small delay) | whenever you choose |
| Controls | can't fast-forward past "now" | can pause, rewind, fast-forward, skip |
| Encoding | encoded and compressed on the fly | encoded in advance, often at several quality levels |
| Delays | latency really matters | a bigger buffer can hide slow patches |