基于 Nginx 的流媒体服务器

说明

1. nginx-rtmp是一个非常优秀的流媒体系统，arut精湛的编程技艺使得无论是用该项目来学习 流媒体服务器设计，还是基于其做二次开发，都非常合适。
2. 由于arut精力早就不在本项目上，所以很遗憾，这个框架有各种这样那样的问题。 这些问题主要来自这几个方面：（1）大量bug没有修复，当然对于一个服务器软件来说， 这是很正常的。（2）未完全完成的部分。例如对多进程的支持，其实还有很多工作没有完成， 导致原框架的多进程在实际中几乎不可用。（3）设计的缺陷。nginx-rtmp中也有一些在设计 之初，arut就没有考虑到或考虑欠周的情况。所以，一方面国内很多公司基于其做流媒体系统， 但另一方面，应该没有谁会直接用它来提供服务，都得花大力气去深度完善甚至改造。
3. 本wiki是nginx-rtmp官方wiki的一个fork，仅是对原框架的说明，会有一些新加的文档。 但不会涉及到bug的修复和新的功能。

nginx-rtmp 模块

项目博客

arut一共维护了两份开发日志：

• http://nginx-rtmp.blogspot.com
• https://rarut.wordpress.com

arut起先在wordpress.com上面做开发记录，后来迁移到了blogspot.com上，所以，如果不是对 评论特别感兴趣的话，阅读第一个地址就够了。

这里必须要强调一下，arut的这些开发日志有很高的价值，通过这些文章，我们可以了解很多代码 背后的东西。强烈建议精读几遍。

配置指令说明

• 英文: https://github.com/arut/nginx-rtmp-module/wiki/Directives
• 中文: 配置指令集

Google 讨论组

• 英文: https://groups.google.com/group/nginx-rtmp
• 俄文: https://groups.google.com/group/nginx-rtmp-ru

特性

• 支持RTMP/HLS/MPEG-DASH直播

• 支持基于RTMP协议的FLV/MP4点播,既支持本地文件点播，也支持通过http从远程拉取文件做点播

• 提供基于relay的分布式支持，主要有两种模式：push和pull

• 支持将直播流录制为flv文件落地到磁盘

• 支持的编码格式是H264/AAC

• 支持使用FFmepg做在线转码

• 提供了HTTP回调支持(publish/play/record/update等)

• 支持通过事件触发来运行外部程序(exec模块)

• 支持通过HTTP请求来控制录制、断开客户端的动作

• 通过精心设计的buffer,使得本系统有着极高的运行效率和极小的内存占用

• 经过测试的客户端包括Wirecast, FMS, Wowza,JWPlayer, FlowPlayer, StrobeMediaPlayback, ffmpeg, avconv, rtmpdump, flvstreamer等等

• 支持通过http请求获取系统内实时的统计数据，统计数据用xml/xsl的形式展现出来

• 兼容Linux/FreeBSD/MacOS/Windows

注意：上面提到的控制和统计功能，分别是用两个http模块来实现的，在多进程的时候这又是 一个雷区:一个http请求只能落在一个worker进程上面。所以，再次强调，如果不进行二次开发， 请不要在多进程时使用这两个功能。

编译

跟所有的nginx第三方模块一样，nginx-rtmp通过如下的方式进行编译:在nginx源码目录下执行

./configure --add-module=/path/to/nginx-rtmp-module
make
make install

为了支持debug模式，在configure的时候带上 --with-debug参数

./configure --add-module=/path/to-nginx/rtmp-module --with-debug

RTMP url格式

rtmp://rtmp.example.com/app[/name]

app - 匹配配置文件中的某个application{}块

name - 由各程序自行处理和解释，可以为空。一般用它来做流名。

多进程支持

nginx-rtmp通过auto_push功能来实现对多进程的支持。大概方法是，每一个被publish到的worker 进程，通过unix域套接字将其接收到的流主动publish到其它各个worker进程。这个功能通过 rtmp_auto_push指令来开启。详见ngx_rtmp_auto_push_module模块。

注意：已经多次强调，nginx-rtmp的多进程支持并不完全，除非你已经非常熟悉源码并能做相应 的修改，否则永远不要在生产环境中开启多进程支持。

配置文件示例-单进程版

rtmp {

    server {

        listen 1935;

        chunk_size 4000;

        # TV mode: one publisher, many subscribers
        application mytv {

            # enable live streaming
            live on;

            # record first 1K of stream
            record all;
            record_path /tmp/av;
            record_max_size 1K;

            # append current timestamp to each flv
            record_unique on;

            # publish only from localhost
            allow publish 127.0.0.1;
            deny publish all;

            #allow play all;
        }

        # Transcoding (ffmpeg needed)
        application big {
            live on;

            # On every pusblished stream run this command (ffmpeg)
            # with substitutions: $app/${app}, $name/${name} for application & stream name.
            #
            # This ffmpeg call receives stream from this application &
            # reduces the resolution down to 32x32. The stream is the published to
            # 'small' application (see below) under the same name.
            #
            # ffmpeg can do anything with the stream like video/audio
            # transcoding, resizing, altering container/codec params etc
            #
            # Multiple exec lines can be specified.

            exec ffmpeg -re -i rtmp://localhost:1935/$app/$name -vcodec flv -acodec copy -s 32x32
                        -f flv rtmp://localhost:1935/small/${name};
        }

        application small {
            live on;
            # Video with reduced resolution comes here from ffmpeg
        }

        application webcam {
            live on;

            # Stream from local webcam
            exec_static ffmpeg -f video4linux2 -i /dev/video0 -c:v libx264 -an
                               -f flv rtmp://localhost:1935/webcam/mystream;
        }

        application mypush {
            live on;

            # Every stream published here
            # is automatically pushed to
            # these two machines
            push rtmp1.example.com;
            push rtmp2.example.com:1934;
        }

        application mypull {
            live on;

            # Pull all streams from remote machine
            # and play locally
            pull rtmp://rtmp3.example.com pageUrl=www.example.com/index.html;
        }

        application mystaticpull {
            live on;

            # Static pull is started at nginx start
            pull rtmp://rtmp4.example.com pageUrl=www.example.com/index.html name=mystream static;
        }

        # video on demand
        application vod {
            play /var/flvs;
        }

        application vod2 {
            play /var/mp4s;
        }

        # Many publishers, many subscribers
        # no checks, no recording
        application videochat {

            live on;

            # The following notifications receive all
            # the session variables as well as
            # particular call arguments in HTTP POST
            # request

            # Make HTTP request & use HTTP retcode
            # to decide whether to allow publishing
            # from this connection or not
            on_publish http://localhost:8080/publish;

            # Same with playing
            on_play http://localhost:8080/play;

            # Publish/play end (repeats on disconnect)
            on_done http://localhost:8080/done;

            # All above mentioned notifications receive
            # standard connect() arguments as well as
            # play/publish ones. If any arguments are sent
            # with GET-style syntax to play & publish
            # these are also included.
            # Example URL:
            #   rtmp://localhost/myapp/mystream?a=b&c=d

            # record 10 video keyframes (no audio) every 2 minutes
            record keyframes;
            record_path /tmp/vc;
            record_max_frames 10;
            record_interval 2m;

            # Async notify about an flv recorded
            on_record_done http://localhost:8080/record_done;

        }


        # HLS

        # For HLS to work please create a directory in tmpfs (/tmp/hls here)
        # for the fragments. The directory contents is served via HTTP (see
        # http{} section in config)
        #
        # Incoming stream must be in H264/AAC. For iPhones use baseline H264
        # profile (see ffmpeg example).
        # This example creates RTMP stream from movie ready for HLS:
        #
        # ffmpeg -loglevel verbose -re -i movie.avi  -vcodec libx264
        #    -vprofile baseline -acodec libmp3lame -ar 44100 -ac 1
        #    -f flv rtmp://localhost:1935/hls/movie
        #
        # If you need to transcode live stream use 'exec' feature.
        #
        application hls {
            live on;
            hls on;
            hls_path /tmp/hls;
        }

        # MPEG-DASH is similar to HLS

        application dash {
            live on;
            dash on;
            dash_path /tmp/dash;
        }
    }
}

# HTTP can be used for accessing RTMP stats
http {

    server {

        listen      8080;

        # This URL provides RTMP statistics in XML
        location /stat {
            rtmp_stat all;

            # Use this stylesheet to view XML as web page
            # in browser
            rtmp_stat_stylesheet stat.xsl;
        }

        location /stat.xsl {
            # XML stylesheet to view RTMP stats.
            # Copy stat.xsl wherever you want
            # and put the full directory path here
            root /path/to/stat.xsl/;
        }

        location /hls {
            # Serve HLS fragments
            types {
                application/vnd.apple.mpegurl m3u8;
                video/mp2t ts;
            }
            root /tmp;
            add_header Cache-Control no-cache;
        }

        location /dash {
            # Serve DASH fragments
            root /tmp;
            add_header Cache-Control no-cache;
        }
    }
}

配置文件示例-多进程版

rtmp_auto_push on;
worker_processes 4;

rtmp {
    server {
        listen 1935;

        application mytv {
            live on;
        }
    }
}