For those who have ever used the Flash Media Server for video streaming, the idea of publishing a stream encapsulated in RTSP (Real Time Streaming Protocol) may seem quite strange, maybe even impossible. This is because the basic (and only) protocol used for FMS client-server communication is the RTMP (and its variations), a proprietary protocol for media streaming, from Adobe. However, in some circumstances the use of an RTMP input is almost impossible, especially when this input stream comes from legacy systems, or from external services. These specific cases require an approach where the content from a RTSP source is delivered using RTMP, that is, a translation from RTSP to RTMP via content repackaging.
The easiest way to perform this translation is using Wowza Media Server, an alternative to FMS that has many interesting features, including the RTSP input support. The problem is that sometimes is impossible to change the video architecture from FMS to other solution, especially when we have developed several applications, or when the whole environment is integrated, up, and running.
In this situation, the intuitive solution would be: we can setup a layer of Wowza Media Server before FMS Servers, working like a translation layer. With this layer, the FMS would receive a RTMP stream exactly like it receives from Flash Media Encoder, making the translation fully transparent. The challenge of this solution is that the Wowza Server cannot publish streams on FMS, so, it cannot act like a FME (from FMS perspective).
To deal with this limitation, we need to change the stream flow paradigm from push to pull, or, in other words, we need to force FMS to get the stream from Wowza. With this architecture configuration, the FMS is no longer a passive component. It is its responsibility to, not only get the video stream, but to perform the failover of the input streams, which can be done through stream multiplexing.
This change in FMS role is only possible if we use server side action script, to connect to Wowza, and to pull the stream flow. Basically, we use NetConnection and Stream classes, to establish a remote connection and to play some content (Wowza stream) through it:
myRemoteConn = new NetConnection(); myRemoteConn.connect("rtmp://wowzaserverhost/streamtest"); myStream = Stream.get("myStream"); myStream.play("my_stream.sdp", 0, -1, true, myRemoteConn);
As we can see, we can use the FMS to delivery RTSP streams without great architecture changes. With Wowza Media Servers and some server side AS, it’s not too hard to make the impossible, possible!