M3u8 format explanation and Practical Application Analysis

What are the advantages of m3u8?
After searching online, there are different opinions. My personal understanding is that it can adapt to multiple bit rates. Based on network bandwidth, the client selects a file suitable for its own bit rate for playing, ensuring the smoothness of the video stream.

In iOS device and Mac, HTTP can be used for distribution. Among them, playlist is a m3u8 file extended by M3U, and the media file is a MPEG2-TS or AAC file (audio only ).

M3u8 files can be used in two scenarios:

Multi-bit rate adaptive stream,

# Extm3u

# EXT-X-STREAM-INF: Program-id = 1, bandwidth = 1280000

Http://example.com/low.m3u8

# EXT-X-STREAM-INF: Program-id = 1, bandwidth = 2560000

Http://example.com/mid.m3u8

# EXT-X-STREAM-INF: Program-id = 1, bandwidth = 7680000

Http://example.com/hi.m3u8

# EXT-X-STREAM-INF: Program-id = 1, bandwidth = 65000, codecs = "mp4a. 40.5"

Http://example.com/audio-only.m3u8

Single bit rate adaptive stream

# Extm3u

# EXT-X-TARGETDURATION: 5220

# Extinf: 5220,

Http://media.example.com/entire.ts

# EXT-X-ENDLIST

The International Standards Organization defines this. rfc doc:
Http://tools.ietf.org/html/draft-pantos-http-live-streaming-06
The m3u8 file is an extension of the M3U File. The extended keyword is defined in the RFC:
Medium:

# EXT-X-TARGETDURATION

Defines the maximum duration of each ts.

# EXT-X-MEDIA-SEQUENCE

Defines the serial number of the first file in the current m3u8 file. Each ts file has a fixed and unique serial number in the m3u8 file. This serial number is used to switch the bit rate during MBR for alignment.

# EXT-X-KEY

Defines the encryption method and the URL of the key file for obtaining 16 bytes of the key file to decode the TS file.

Attribute:

Method

URL

# EXT-X-PROGRAM-DATE-TIME

Absolute Time of the first file

# EXT-X-ALLOW-CACHE

Whether to agree to the cache.

# EXT-X-ENDLIST

Indicates the end of The m3u8 file. Live m3u8 does not have this tag.

# EXT-X-STREAM-INF

Attribute:

Bandwidth specifies the bit rate

Unique id of Program-ID

Codecs specifies the stream encoding type

# EXT-X-DISCONTINUITY

When this tag is encountered, the following attributes are changed:

File Format

Number and type of tracks

Encoding Parameters

Encoding Sequence

Timestamp Sequence

# EXT-X-VERSION this attribute can not be used, can not

M3u8 is divided into top-level m3u8 and second-level m3u8. Top-level m3u8 is mainly applicable to multiple bit rates. Second-level m3u8 is the real slicing file,

By default, the client will first select the request with the highest bit rate. if it finds that the bit rate does not reach, it will request a stream with a low bit rate.

A top-level m3u8 file in actual use is as follows:

# Extm3u
# EXT-X-STREAM-INF: Program-id = 201273221265, bandwidth = 358400
11. m3u8
# EXT-X-STREAM-INF: Program-id = 201273221265, bandwidth = 972800
22. m3u8

The above top-level m3u8 file defines two level-2 files, 11. m3u8 and 22. m3u8. The client will choose one of them to get its content.

The content of level 2 m3u8 files is as follows:

# Extm3u
# EXT-X-VERSION: 1
# EXT-X-TARGETDURATION: 10
# EXT-X-MEDIA-SEQUENCE: 0
# Extinf: 3,
1-4.ts
# Extinf: 8,
1-6.ts
# Extinf: 8,
1-8.ts
# Extinf: 8,
1-10.ts
# Extinf: 8,
1-12.ts
# Extinf: 8,
1-14.ts
# Extinf: 8,
1-16.ts
# Extinf: 9,
1-18.ts
# Extinf: 6,
1-0000ts
# Extinf: 8,
1-22.ts
# Extinf: 9,
1-24.ts
# Extinf: 3,
1-26.ts
# EXT-X-ENDLIST

After the client obtains the above level 2 m3u8 file, it will continue to request the file in it, and then it will be able to play back.

The above describes the on-demand video and live video. In m3u8 files, the property tells the live video, and the client regularly requests a new m3u8 file.

Http://www.ioncannon.net/programming/452/iphone-http-streaming-with-ffmpeg-and-an-open-source-segmenter/

M3u8 format explanation and Practical Application Analysis