ActionScript Publisher

This is a Flash app that allows live-streaming via RTMP from a web browser.

It depends on an EC2 Image with the nginx-rtmp-module installed, along with a custom ffmpeg with the "non-free" x264 and libfdk_aac linked-in.

Codecs

The Flash H.264 encoder is unreliable (at least when ffmpeg tries to decode it). Also, Flash Player doesn't support audio encoding in AAC. As such, the approach we take is to encode video using Sorensen (flv1), audio using Speex, and then use ffmpeg on the server to transcode.

If Adobe ever fixes their H.264 encoder, we could just do a passthrough for video with ffmpeg. Likewise, if they add an AAC encoder, we could do a passthrough for audio. If both issues are addressed, we wouldn't need the EC2 instance any longer and could stream directly to EdgeCast.

Debugging

For ease of debugging, it uses the flash.external.ExternalInterface class do push all of its logging into JavaScript via console.log.

EC2 Image

How to Build

• Install nginx-rtmp-module
• Install libspeex-dev: sudo apt-get install libspeex-dev
• Custom build ffmpeg from source

Nginx Config

error_log /var/log/nginx/error.log;

rtmp {
  server {

    listen 1935;
    chunk_size 4096;

    application live {
      live on;

      #record all;
      #record_path /tmp;
      #record_suffix -%d-%b-%y-%T.flv;

      exec /home/ubuntu/bin/ffmpeg -i rtmp://localhost:1935/${app}/${name} -c:v libx264 -preset ultrafast -crf 23 -maxrate 2000k -c:a libfdk_aac -profile:a aac_he -f flv rtmp://stream.lax.cine.io/20C45E/stages/${name}?${args} 2>>/tmp/ffmpeg.log;
    }
  }
}

Acknowlegements

This code is based on the work done by Davide Bertola in the webproducer project.