Review: Wowza Media Server 2

The URL string is fairly straightforward, with the protocol header being anything from RTSP to RTMP to HTTP, depending on which device, player, or delivery protocol is used.

Wowza defaults to port 1935 to serve up content, and any files that are set to be served up are designated by the application as being in the VOD folder (even though they're really in the Content folder).

The designation in the URL string that comes just before the filename ("mp4:") designates that the file the server will need to address is H.264-based, regardless of its three-letter extension.

Minimal Prep; Multiple Protocols

The only prep work that one needs to do for single-bitrate files is to make sure the URLs are available for any protocol or device on which the original H.264-based MP4 or M4V file will be played:

• Apple iPhone URLs add "playlist.m3u8" after the rest of the URL, like this: http://[wowza server]:1935/vod/mp4:filename.mp4/playlist.m3u8. This is true regardless of whether the iPhone will be doing adaptive bitrate or just single bitrate file playback.

• Flash video playback, using Wowza's sample Flash player, is slightly different in that the server and stream information are split apart. The Flash player prompts server information ("rtmp://localhost/vod" works if you're playing content on the Flash player from the same server) and then the stream information ("mp4:filename.mp4").

• Microsoft Silverlight Smooth Streaming is also played back from an included Silverlight player, a new addition to the 2.1.2 version server download. Both the Flash and Silverlight sample players are helpful for testing and familiarity purposes.

• Silverlight adds a "/Manifest" to the end of the URL string to designate that the manifest is available for playback, so the URL looks like this: http://[wowzaserver]:1935/vod/mp4: sample.mp4/Manifest (see Figure 2).

• RTSP playback is very straightforward: rtsp://[wowzaserver]:1935/vod/mp4: filename.mp4

When it comes to stream output, it's easy to see where Wowza Media Server really shines. Because what's most interesting about Wowza Media Server is all the preparation work you won't have to do before putting a VOD file into the Content folder.

For other multiprotocol servers, all the manifests and playlists need to be created ahead of time so that the server can simply serve up each set of files and manifests to the appropriate device. Wowza, on the other hand, uses standard MP4 or M4V files and then creates the manifest or playlist during the stream serving process.

For ABR, however, Wowza makes use of a SMIL file, which must be prepared ahead of time (Figure 3). Readers from the early days of streaming will remember SMIL as the language used by RealPlayer to designate which of several files should be chosen for playback with the player or browser. Streaming servers often offered up between three and five different bitrates that were referenced by the SMIL file, so this method of delivery was often known as multibitrate (MBR) streaming. Only one stream was chosen at the outset, though, and playback was locked to that bitrate regardless of what type of network congestion ensued.

ABR uses the same number of bitrates as MBR, but it can use any of the different bitrates throughout the course of playback. To do so, the files must be segmented into 2- to 10-second chunks, and then the server designates which bitrate will play back for that period of time.

Wowza not only changes protocols (from HTTP to RTMP to RTSP) but also creates segments for sets of files that share all the same parameters, with the exception of the bitrate. To do so, Wowza is using SMIL as an aid to its on-the-fly segmentation for ABR playback.

In the version I tested, Wowza Media Server 2.1.2, the server supports segmentation of Apple and Microsoft content for iPhone and Silverlight players, respectively.

"Wowza performs all the necessary segmentation," Alex Dobrushin, chief marketing officer of Wowza Media Systems, told me after I'd finished up my single-bitrate protocol conversion testing and was moving into multiple bitrate tests.
"That is the key to Wowza's unified workflow.

The same standard MP4 file can be streamed simultaneously to Flash RTMP or HTTP, Silverlight, QuickTime (RTSP), iPhone, etc."

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