ffplayout/docs/preview_stream.md

### Preview Stream

When you are using the web frontend, you may wonder how to get a preview in the player. The default installation creates an HLS playlist, and the player uses this, but the HLS mode is not always utilized; instead, the stream output mode is activated.

So if you stream to an external server, you have different options to get a preview stream for your player. The simplest option would be to obtain an m3u8 playlist address from your external target, such as: https://example.org/live/stream.m3u8. You can use this in the configuration section of the frontend.

Another option (which has not been tested) is to add an HLS output option to your streaming parameters.

The next option is to install an RTMP server locally and create your preview stream there. In the following lines, this is described in more detail.

The ffplayout engine has no special preview config parameters, but you can add your settings to the **output_param**, like:

```YAML
    -s 512x288
    -c:v libx264
    -crf 24
    -x264-params keyint=50:min-keyint=25:scenecut=-1
    -maxrate 800k
    -bufsize 1600k
    -preset ultrafast
    -tune zerolatency
    -profile:v Main
    -level 3.1
    -c:a aac
    -ar 44100
    -b:a 128k
    -flags +global_header
    -f flv rtmp://127.0.0.1/live/stream
    ...
```

In this documentation, we assume that you are using [SRS](https://github.com/ossrs/srs) at least for the preview stream. The most stable solution is previewing over HLS, but it is also possible to use [HTTP-FLV](https://github.com/ossrs/srs/wiki/v4_EN_DeliveryHttpStream) for lower latency.

To get this working, we need to follow some steps.

#### The first step is to compile and install SRS:

```BASH
# install some tool for compiling
apt install curl wget net-tools git build-essential autoconf automake libtool pkg-config gperf libssl-dev

cd /opt/

# get SRS
git clone https://github.com/ossrs/srs.git

cd srs/trunk

# get correct branch
git checkout 4.0release

./configure --ffmpeg-fit=off

make -j4

# install SRS to /usr/local/srs
make install

```

Now we need a systemd service to start SRS automatically. Create the file:

**/etc/systemd/system/srs.service**

with this content:

```INI
Description=SRS
Documentation=https://github.com/ossrs/srs/wiki
After=network.target

[Service]
Type=forking
ExecStartPre=/usr/local/srs/objs/srs -t -c /etc/srs/srs.conf
ExecStart=/usr/local/srs/objs/srs -c /etc/srs/srs.conf
ExecStop=/bin/kill -TERM \$MAINPID
ExecReload=/bin/kill -1 \$MAINPID
Restart=always
RestartSec=3

[Install]
WantedBy=multi-user.target
```

Then create the config for SRS under **/etc/srs/srs.conf** with this content:

```NGINX
listen              1935;
max_connections     20;
daemon              on;
pid                 /usr/local/srs/objs/srs.pid;
srs_log_tank        console; # file;
srs_log_file        /var/log/srs.log;
ff_log_dir          /tmp;
srs_log_level       error;

http_server {
    enabled         on;
    listen          127.0.0.1:8080;
    dir             ./objs/nginx/html;
}

stats {
    network         0;
    disk            sda vda xvda xvdb;
}

# for normal HLS streaming
vhost __defaultVhost__ {
    enabled             on;

    play {
        mix_correct     on;
    }

    # switch enable off, for hls preview
    http_remux {
        enabled     on;
        mount       [vhost]/[app]/[stream].flv;
    }

     # switch enable off, for http-flv preview
    hls {
        enabled         on;
        hls_path        /var/www/srs;
        hls_fragment    6;
        hls_window      3600;
        hls_cleanup     on;
        hls_dispose     0;
        hls_m3u8_file   live/stream.m3u8;
        hls_ts_file     live/stream-[seq].ts;
    }
}

```

Now you can enable and start SRS with: `systemctl enable --now srs` and check if it is running: `systemctl status srs`.

#### Configure Nginx

We assume that you have already installed Nginx and are using it for the frontend. Open the frontend config **/etc/nginx/sites-enabled/ffplayout.conf** and add a new location to it:

```NGINX
location /live/stream.flv {
    proxy_pass http://127.0.0.1:8080/live/stream.flv;
}
```

Full config looks like:

```NGINX
server {
    listen 80;

    server_name ffplayout.example.org;

    gzip on;
    gzip_types text/plain application/xml text/css application/javascript;
    gzip_min_length 1000;

    charset utf-8;

    client_max_body_size 7000M; # should be desirable value

    add_header X-Frame-Options SAMEORIGIN;
    add_header X-Content-Type-Options nosniff;
    add_header X-XSS-Protection "1; mode=block";
    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;

    location / {
        proxy_set_header Host $http_host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_read_timeout 36000s;
        proxy_connect_timeout 36000s;
        proxy_send_timeout 36000s;
        proxy_buffer_size 128k;
        proxy_buffers 4 256k;
        proxy_busy_buffers_size 256k;
        send_timeout 36000s;
        proxy_pass http://127.0.0.1:8787;
    }

    location /live/ {
        alias /var/www/srs/live/;
    }

    location /live/stream.flv {
        proxy_pass http://127.0.0.1:8080/live/stream.flv;
    }
}
```

Of course, in production, you should have an HTTPS directive as well, but this step is up to you.

Restart Nginx.

You can (re)start ffplayout, and when you have set everything up correctly, it should run without errors.

You can now go to your frontend configuration and change the `player_url` to: `http://[domain or IP]/live/stream.flv` or `http://[domain or IP]/live/stream.m3u8`. Save and reload the page. When you go to the player tab, you should see the preview video.