Step 1: Preparing Your Video For Adaptive Bitrate Streaming

Developers - get the player source code

The Adaptive Bitrate Streaming enabled by Autobahn HD makes sure viewers always see the best available encoding for their current network conditions. It doesn’t, however, do real-time transcoding on the fly. Instead it relies on multiple encodings of the same content, collectively called a Media Group.

When assembling a media group start with the highest bitrate you’re able to support with your source content and willing to support on your playback site. Using Adobe or third party tools create a FLV video using VP6 or Sorensen encoding with the desired audio and video bitrates. Continue by creating additional encodings of the same video, decreasing the video bitrate by 200 or 300 Kbps each step. Bitrates should be even multiples of 100 Kbps.

It’s best to leave the audio bitrate the same across all the encodings as viewers notice shifts in audio quality much more than those in video quality. As you decrease the video bitrate you may find it necessary to decrease the frame size/resolution in pixels to maintain an acceptable viewing experience. It is helpful but not required that filenames of the various encodings be identical but for the bitrate and possibly screen resolution. Whether you include the bitrate in the filename or opt not to, do make sure you note the exact bitrate in kilobits per second for each file as they’ll be required later.

For example, if you have a source video named ElephantsDream.mov with a bitrate of 5Mbps and you would like the highest bitrate available for viewing to be 1.5 Mbps you would use your transcoding tool to produce the following files:

• ElephantsDreamAbbr_1280x720_vp6_1400Kbps.flv
• ElephantsDreamAbbr_1280x720_vp6_1200Kbps.flv
• ElephantsDreamAbbr_1280x720_vp6_800Kbps.flv
• ElephantsDreamAbbr_320x180_vp6_500Kbps.flv

With each containing the same content at the bitrate and resolution indicated in the filename.Once you’ve created the components of your Media Group upload them to your standard Web Server — there is no need for custom server software or configuration. Acceleration is only possible if your server supports HTTP Range: requests, which is standard for all modern HTTP servers.

With the files uploaded make note of the URLs where each file can be accessed as determined by your web server’s hostname and configuration. In our example the four files identified above correspond to these URLs:

• http://showcase.swarmcast.com/ElephantsDreamAbbr_1280x720_vp6_1400Kbps.flv
• http://showcase.swarmcast.com/ElephantsDreamAbbr_1280x720_vp6_1200Kbps.flv
• http://showcase.swarmcast.com/ElephantsDreamAbbr_1280x720_vp6_800Kbps.flv
• http://showcase.swarmcast.com/ElephantsDreamAbbr_320x180_vp6_500Kbps.flv

All of the files referenced above can be found in the archive at http://showcase.swarmcast.com/AutobahnAdaptiveBitrateStreamingExample.zip.Next: Step 2: Create a Swarmcast Media Metadata file for each of your encodings and upload them to your web server.