软硬件环境

  • ubuntu 16.04
  • Android Studio 2.1.3
  • OTT BOx with android 5.1.1
  • nginx 1.11.3
  • nginx-rtmp-module
  • VLC

前言

Android RTMP直播(续)介绍了HLS协议相关的基础内容,本文将继续深入学习HLS的其它高级特性.

服务端多码率支持

nginx.conf
#user  nobody;
worker_processes  auto;

rtmp_auto_push on;

error_log  logs/error.log;
error_log  logs/error.log  notice;
error_log  logs/error.log  info;

#pid        logs/nginx.pid;

events {
    worker_connections  1024;
}

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 /opt/www/vod;
#        }

#        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 /opt/www/live;
            hls_nested on;

            hls_variant _low BANDWIDTH=800000;
            hls_variant _mid BANDWIDTH=1200000;
            hls_variant _hi  BANDWIDTH=2000000;
        }

        # 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      8081;

        location / {
            root /opt/www/;
        }

        # 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 /home/djstava/Workshop/Web/nginx-rtmp-module/;
        }

        location /hls {
            # Serve HLS fragments
            types {
                application/vnd.apple.mpegurl m3u8;
                video/mp2t ts;
            }

            root /opt/www/;
            add_header Cache-Control no-cache;
        }

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

主要看看application hls的内容

application hls {
            live on;
            hls on;
            hls_path /opt/www/live;
            hls_nested on;

            hls_variant _low BANDWIDTH=800000;
            hls_variant _mid BANDWIDTH=1200000;
            hls_variant _hi  BANDWIDTH=2000000;
        }

这里设定当带宽分别为800k 1200k 2000k的时候,终端都播放相对应的m3u8索引文件

ffmpeg推流

这里需要利用ffmpeg推送3路不同的流,对应上面提到的低 中 高

ffmpeg -re -i ~/Videos/xjcy.mp4 -vcodec copy -acodec copy -b:v 800k -b:a 32k -f flv rtmp://10.10.10.59/hls/livestream_low
ffmpeg -re -i ~/Videos/xjcy.mp4 -vcodec copy -acodec copy -b:v 1200k -b:a 64k -f flv rtmp://10.10.10.59/hls/livestream_mid
ffmpeg -re -i ~/Videos/xjcy.mp4 -vcodec copy -acodec copy -b:v 2000k -b:a 128k -f flv rtmp://10.10.10.59/hls/livestream_hi

推送开始后,hls的root目录下就会生成相应的文件内容,如下图所示

nginx_ffmpeg_variant

此时livestream.m3u8文件内容为

#EXTM3U
#EXT-X-VERSION:3
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=800000
livestream_low/index.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=1200000
livestream_mid/index.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=2000000
livestream_hi/index.m3u8

相应的,播放链接为 http://10.10.10.59:8081/live/livestream.m3u8,播放器需要做的就是根据自身的网络状况,切换到其它的索引文件.

直播节目的录制

直播进行的同时一般都会有本地录制的需求,nginx-rtmp-module提供了这个功能,接下来实践一下.还是看nginx.conf配置文件

application hls {
            live on;
            hls on;
            hls_path /opt/www/live;
            hls_nested on;

            hls_variant _low BANDWIDTH=800000;
            hls_variant _mid BANDWIDTH=1200000;
            hls_variant _hi  BANDWIDTH=2000000;

            recorder all {
                record all;
                record_suffix -%Y-%m-%d-%H_%M_%S.flv;
                record_max_size 200000K;
                record_path /opt/www/record;
            }
        }

record all录制所有内容,也可以只录音频或者视频.

推流后/opt/www/record路径下就会自动生成带对应时间戳的flv文件,用vlc测试播放OK.

nginx_ffmpeg_record

时移电视

要想实现时移电视(这里指的是服务器端)的话,首先需要在服务器上保留足够的切片文件,比如说你提供1小时的时移,就意味着要有1小时的切片文件,而且索引文件中包含前1小时的切片序列.

application hls {
            live on;
            hls on;
            hls_path /opt/www/live;
            hls_continuous on;
            hls_sync 100ms;
            hls_nested on;
            hls_playlist_length 5m;
            hls_fragment 10s;

            hls_variant _low BANDWIDTH=800000;
            hls_variant _mid BANDWIDTH=1200000;
            hls_variant _hi  BANDWIDTH=2000000;

            #exec /home/djstava/Workshop/Web/nginx-1.11.3/build/test.sh;
            #exec_kill_signal term;

            #recorder all {
            #    record all;
            #    record_suffix -%Y-%m-%d-%H_%M_%S.flv;
            #    record_max_size 6200000K;
            #    record_path /opt/www/record;
            #}
        }

hls_fragment指的是切片文件的长度,这里是10秒,hls_playlist_length指的是索引文件的长度,我这里设的是5分钟.推流开始后,你到切片生成的目录,会发现*.m3u8文件包含了30个ts序列.所以,在上面这种情况下,就只能进行5分钟的时移,当播放进度到达当前直播点时则继续回到直播状态.

执行外部shell脚本

比如有个脚本test.sh,内容如下

#!/bin/bash

on_die ()
{
    # kill all children
    pkill -KILL -P $$
}

trap 'on_die' TERM
ffmpeg -re -i /home/djstava/Videos/ygdx.mp4  -vcodec copy -acodec copy -f flv rtmp://10.10.10.48/hls/ygdx &
wait

我这里把它放在hls application中执行,则nginx.conf应如下

application hls {
            live on;
            hls on;
            hls_path /opt/www/live;
            hls_continuous on;
            hls_sync 100ms;
            hls_nested on;
            hls_playlist_length 5m;
            hls_fragment 10s;

            hls_variant _low BANDWIDTH=800000;
            hls_variant _mid BANDWIDTH=1200000;
            hls_variant _hi  BANDWIDTH=2000000;

            exec /home/djstava/Workshop/Web/nginx-1.11.3/build/test.sh;
            exec_kill_signal term;

            #recorder all {
            #    record all;
            #    record_suffix -%Y-%m-%d-%H_%M_%S.flv;
            #    record_max_size 6200000K;
            #    record_path /opt/www/record;
            #}
        }

当hls服务正常启动时(如上面写过的ffmpeg推流动作),外部脚本test.sh也被执行了.脚本中捕捉了退出的中断信号,也就说,如果ffmpeg推流动作中断了,那么test.sh脚本也就不再执行了.

制作RAMDISK

为了提高HLS的读写效率,可以把切片和索引文件操作放在内存中进行.

mount -t tmpfs -o size=512m tmpfs /opt/www/live

参考文献

1 https://github.com/arut/nginx-rtmp-module/wiki/Directives


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