38-how-to-stream-video-over-http.md

slug	38-how-to-stream-video-over-http
id	38-how-to-stream-video-over-http
title	How to stream video over HTTP for mobile devices? HTTP Live Streaming (HLS)
date	2018-09-07 21:32
comments	true
tags	system design
description	Video service over Http for mobile devices has two problems: limited memory or storage and unstable network connection and variable bandwidth. HTTP live streaming solve this with separation of concerns, file segmentation, and indexing.
references	https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/StreamingMediaGuide/HTTPStreamingArchitecture/HTTPStreamingArchitecture.html#//apple_ref/doc/uid/TP40008332-CH101-SW2

Motivation

Video service over Http Live Streaming for mobile devices, which...

1. ==has limited memory/storage==
2. suffers from the unstable network connection and variable bandwidth, and needs ==midstream quality adjustments.==

Solution

1. Server-side: In a typical configuration, a hardware encoder takes audio-video input, encodes it as H.264 video and AAC audio, and outputs it in an MPEG-2 Transport Stream

   1. the stream is then broken into a series of short media files (.ts possibly 10s) by a software stream segmenter.
   2. The segmenter also creates and maintains an index(.m3u8) file containing a list of the media files.
   3. Both the media fils and the index files are published on the web server.

2. Client-side: client reads the index, then requests the listed media files in order and displays them without any pauses or gaps between segments.

Architecture