H5 live video broadcast

EXTM3U                       m3u file header

EXT-X-MEDIA-SEQUENCE      The sequence number of the first TS fragment

EXT-X-TARGETDURATION                    Maximum duration of filmTS

EXT - EXT-X- ENDLIST                          m3u8 file end character

#EXTINF                                                                               Specify the duration (seconds) of each media segment (ts), which is only valid for the URI following it

#mystream-12.ts

ts file:

The request process of HLS is:
1 http request m3u8 url.
2 The server returns an m3u8 playlist. This playlist is updated in real time. Generally, 5 data URLs are given at a time.
3 The client parses the m3u8 playlist, then requests the url of each segment in sequence to obtain the ts data stream.

Simple process:

3 HLS live broadcast delay

We know that the hls protocol will The live stream is divided into short videos for downloading and playing, so assuming that the list contains 5 ts files, and each TS file contains 5 seconds of video content, then the overall delay is 25 seconds. Because when you see these videos, the host has already recorded the video and uploaded it, so there is a delay caused by this. Of course, you can shorten the length of the list and the size of a single ts file to reduce latency. In the extreme, you can reduce the list length to 1 and the ts duration to 1 second. However, this will increase the number of requests and increase server pressure. When the network speed is slow, Timing causes more buffering, so Apple’s officially recommended ts duration is 10s, so this will cause a 30s delay. Reference: https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/StreamingMediaGuide/FrequentlyAskedQuestions/FrequentlyAskedQuestions.html

Live video can be roughly divided into:

Simple process:

Let’s first clarify a few concepts:

Audio
Encoding: Similar to video encoding, the original audio stream is encoded, uploaded, decoded, and played in the player according to certain standards. Of course, there are also many encoding standards for audio, such as PCM encoding. , WMA encoding, AAC encoding, etc. The audio encoding method supported by our HLS protocol here is AAC encoding. The following will use the camera on ios to collect audio and video data, which is mainly divided into the following steps:

Session and AVCaptureDevice. 2 Encode H264 for video and AAC for audio. There are encapsulated encoding libraries in ios to encode audio and video. 3 Assemble the encoded audio and video data into packets;
4 Establish an RTMP connection and push it to the server.

ps: Since most coding libraries are written in

, you need to compile them when you use them. For ios, you can use the already compiled coding libraries. x264 encoding: https://

hub.com/kewlbear/x264-iosfaac encoding: https://github.com/fflydev/faac- ios-build

ffmpeg encoding: https://github.com/kewlbear/FFmpeg-iOS-build-script

About if you want to add some special effects to the video, such as adding filters, etc. , generally use the filter library before encoding, but this will also cause some time consuming, resulting in a certain delay in uploading video data.

Simple process:

6 What is the ffmpeg mentioned earlier?

Like the previous x264, ffmpeg is actually a set of encoding libraries. Similar to Xvid, Xvid is a codec based on the MPEG4 protocol, and x264 is an encoder based on the H.264 protocol. ffmpeg integrates various audio and video encoding and decoding protocols. By setting parameters, encoding and decoding based on MPEG4, H.264 and other protocols can be completed. The demo here uses the x264 encoding library.

7 What is RTMP?

Real Time Messaging Protocol (RTMP for short) is a set of video live broadcast protocols developed by Macromedia and now owned by Adobe. Like HLS, it can be applied to live video broadcasts. The difference is that RTMP is based on flash and cannot be played in iOS browsers, but its real-time performance is better than HLS. Therefore, this protocol is generally used to upload video streams, that is, the video streams are pushed to the server.

Here is a comparison between hls and rtmp:

8 Push flow

The so-called push flow is Send our encoded audio and video data to the video streaming server. Generally, rtmp is used to push the stream. You can use the third-party library librtmp-iOS to push the stream. librtmp encapsulates some core api is for users to call. If you find it troublesome, you can use the ready-made ios video streaming SDK, which is also based on rtmp, https://github.com/runner365/LiveVideoCoreSDK

9 Push server setup

Simple push server setup. Since the video streams we upload are based on the rtmp protocol, the server must also support rtmp. You probably need the following Steps:

1 Installan nginx server.

2 Install nginx’s rtmp extension. Currently, the most commonly used one is https://github.com/arut/nginx-rtmp-module

3 Configure nginx conf file: