Starting with Wowza 4.0 the new default container is MP4, this used to be FLV, so to playback the streams you needed to specify the mp4 container. Also, prior to Wowza 4.0, you needed to use the mp4: prefix to record to mp4:
One other usage is with sub-directories. If a file is in /content/subfolder you would need to use this URL:
For some players (JWPlayer for example) to stream on demand files from a Wowza media server, you must specify the container format for the video asset. This is typically accomplished by adding a stream prefix to the VOD asset to create the stream name in playback URLs. The stream prefix specifies the container format for RTMP streaming. For example, in the following playback URL:
The mp4: stream name prefix specifies that the QuickTime container format is used for the sample.mp4 video.
In Wowza Streaming Engine Manager, you can specify a default container format so that the corresponding stream prefix isn't required in playback URLs. The Streaming Engine has two settings:
I hope this helps.