science

Media Source Extensions

Media Source Extensions is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Media Source Extensions rather than just read about it. In short: Media Source Extensions (MSE) is a W3C specification that allows JavaScript to send byte streams to media codecs within web browsers that support HTML video and audio. Among other possible uses, this allows the implementation of client-side prefetching and buffering code for streaming media entirely in JavaScript.

Key takeaways

Media Source Extensions belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Media Source Extensions to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Media Source Extensions from memory before moving on to harder problems.

Reference excerpt

Media Source Extensions (MSE) is a W3C specification that allows JavaScript to send byte streams to media codecs within web browsers that support HTML video and audio. Among other possible uses, this allows the implementation of client-side prefetching and buffering code for streaming media entirely in JavaScript. It is compatible with, but should not be confused with, the Encrypted Media Extensions (EME) specification, and neither requires the use of the other, although many EME implementations are only capable of decrypting media data provided via MSE. Netflix announced experimental support in June 2014 for the use of MSE playback on the Safari browser on the OS X Yosemite beta release. YouTube started using MSE in its HTML5 player in September 2013.

Browser support The Media Source Extensions API is widely supported across all modern web browsers, with the only exception being iPhone-family devices (although it is supported on iPadOS). Firefox 37 already had a subset of MSE API available for use with only YouTube in Firefox 37 on Windows Vista or later only, while Mac OS X version had in enabled starting version 38.

Minor browsers Pale Moon from version 27.0, since 22 November 2016.

Players Akamai's Adaptive Media Player, which includes Dash.js, HLS.js and advanced QUIC protocol playback from Akamai Edge Servers Google's Shaka Player, an open source javascript player library for HTML5 MSE and EME video with DASH and HLS support bitmovin's bitdash MPEG-DASH player for HTML5 MSE and EME, with Flash fallback dash.js, a reference implementation for HTML5 MSE and EME Canal+'s rx-player for HTML5 MSE and EME (Live and On Demand) Dailymotion's hls.js for HTML5 MSE JW Player 7 and later for MPEG-DASH using HTML5 MSE and EME Azure Media Player supports MSE, EME, DASH, HLS, Flash, and Silverlight. Streaming URLs are published in an ism/manifest Unreal HTML5 player uses MSE for low latency (sub-second) live playback of streams sent via WebSockets by Unreal Media Server

See also HTML video Dynamic Adaptive Streaming over HTTP (DASH) WebRTC

References

Worked examples

Example 1 — a first encounter with Media Source Extensions

Start with the simplest possible case. Write down what Media Source Extensions claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Media Source Extensions before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Media Source Extensions ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Media Source Extensions

In research: Media Source Extensions appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Media Source Extensions in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Media Source Extensions is common in secondary-school and first-year university syllabi. It links to neighbouring topics HTML5, Streaming media systems, so understanding it makes those chapters shorter.
In everyday life: Look for Media Source Extensions outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Media Source Extensions in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Media Source Extensions means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Media Source Extensions out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Media Source Extensions in simple terms?

Why does Media Source Extensions matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Media Source Extensions?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Media Source Extensions.