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Wim Taymans
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docs/README
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docs/README
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@ -1,7 +1,7 @@
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README
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------
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(Last updated on Fri 30 jan 2009, version 0.10.1.1)
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(Last updated on Fri 26 oct 2012, version 0.11.89.1)
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This HOWTO describes the basic usage of the GStreamer RTSP libraries and how you
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can build simple server applications with it.
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@ -10,11 +10,11 @@ can build simple server applications with it.
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The server relies heavily on the RTSP infrastructure of GStreamer. This includes
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all of the media acquisition, decoding, encoding, payloading and UDP/TCP
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streaming. We use the gstrtpbin element for all the session management. Most of
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streaming. We use the rtpbin element for all the session management. Most of
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the RTSP message parsing and construction in the server is done using the RTSP
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library that comes with gst-plugins-base.
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The result is that the server is rather small (a few 1000 lines of code) and easy
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The result is that the server is rather small (a few 6000 lines of code) and easy
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to understand and extend. In its current state of development, things change
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fast, API and ABI are unstable. We encourage people to use it for their various
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use cases and participate by suggesting changes/features.
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@ -23,9 +23,11 @@ can build simple server applications with it.
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that provide reasonable default functionality but has a fair amount of hooks
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to override the default behaviour.
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The server currently integrates with the glib mainloop nicely. It is also a
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heavy user of multiple threads. It's currently not meant to be used in
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high-load scenarios and you should probably not put it on a public IP address.
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The server currently integrates with the glib mainloop nicely. The network part
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is currently single threaded but the GStreamer bits are a heavy user of multiple
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threads. It's currently not meant to be used in high-load scenarios and because
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no security audit has been done, you should probably not put it on a public
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IP address.
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* Initialisation
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@ -173,7 +175,7 @@ can build simple server applications with it.
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A freshly created GstRTSPMedia object from the factory initially only contains a
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GstElement containing the elements to produce the RTP streams for the media and
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a GArray of GstRTSPMediaStream objects describing the payloader and its source
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a GPtrArray of GstRTSPStream objects describing the payloader and its source
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pad. The media is unprepared in this state.
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Usually the url will determine what kind of pipeline should be created. You can
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@ -194,7 +196,7 @@ can build simple server applications with it.
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After creating the GstRTSPMedia object from the factory, it can be prepared
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with gst_rtsp_media_prepare(). This method will put those objects in a
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GstPipeline and will construct and link the streaming elements and the
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gstrtpbin session manager object.
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rtpbin session manager object.
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The _prepare() method will then preroll the pipeline in order to figure out the
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caps on the payloaders. After the GstRTSPMedia prerolled it will be in the
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@ -205,8 +207,8 @@ can build simple server applications with it.
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used for sending and receiving RTP/RTCP from clients. These port numbers will
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have to be negotiated with the client in the SETUP requests.
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When preparing a GstRTSPMedia, a multifdsink is also constructed for streaming
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the stream over TCP when requested.
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When preparing a GstRTSPMedia, an appsink and asppsrc is also constructed
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for streaming the stream over TCP when requested.
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* the GstRTSPClient object
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@ -226,7 +228,8 @@ can build simple server applications with it.
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connection open with the server. Since is possible for a client to open and close
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the TCP connection between requests, we cannot store the state related
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to the configured RTSP session in the GstRTSPClient object. This server state
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is instead stored in the GstRTSPSession object.
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is instead stored in the GstRTSPSession object, identified with the session
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id.
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* GstRTSPSession
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@ -242,12 +245,13 @@ can build simple server applications with it.
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can refer to its previously configured state by sending the session id in
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further requests.
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A client will then use the session id to configure one or more streams,
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identified by their url. This information is kept in a GstRTSPSessionMedia
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structure that is refered to from the GstRTSPSession.
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A client will then use the session id to configure one or more
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GstRTSPSessionMedia objects, identified by their url. This SessionMedia object
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contains the configuration of a GstRTSPMedia and its configured
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GstRTSPStreamTransport.
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* GstRTSPSessionMedia and GstRTSPSessionStream
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* GstRTSPSessionMedia and GstRTSPStreamTransport
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A GstRTSPSessionMedia is identified by a URL and is referenced by a
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GstRTSPSession. It is created as soon as a client performs a SETUP operation on
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@ -256,13 +260,13 @@ can build simple server applications with it.
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for each of the streams in the media.
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Each SETUP request performed by the client will configure a
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GstRTSPSessionStream object linked to by the GstRTSPSessionMedia structure.
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GstRTSPStreamTransport object linked to by the GstRTSPSessionMedia structure.
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It will contain the transport information needed to send this stream to the
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client. The GstRTSPSessionStream also contains a link to the GstRTSPMediaStream
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client. The GstRTSPStreamTransport also contains a link to the GstRTSPStream
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object that generates the actual data to be streamed to the client.
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Note how GstRTSPMedia and GstRTSPMediaStream (the providers of the data to
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stream) are decoupled from GstRTSPSessionMedia and GstRTSPSessionStream (the
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Note how GstRTSPMedia and GstRTSPStream (the providers of the data to
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stream) are decoupled from GstRTSPSessionMedia and GstRTSPStreamTransport (the
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configuration of how to send this stream to a client) in order to be able to
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send the data of one GstRTSPMedia to multiple clients.
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@ -270,15 +274,15 @@ can build simple server applications with it.
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* media control
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After a client has configured the transports for a GstRTSPMedia and its
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GstRTSPMediaStreams, the client can play/pause/stop the stream.
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GstRTSPStreams, the client can play/pause/stop the stream.
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The GstRTSPMedia object was prepared in the DESCRIBE call (or during SETUP when
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the client skipped the DESCRIBE request). As seen earlier, this configures a
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couple of multiudpsink and udpsrc elements to respectively send and receive the
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couple of udpsink and udpsrc elements to respectively send and receive the
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media to clients.
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When a client performs a PLAY request, its configured destination UDP ports are
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added to the GstRTSPMediaStream target destinations, at which point data will
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added to the GstRTSPStream target destinations, at which point data will
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be sent to the client. The corresponding GstRTSPMedia object will be set to the
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PLAYING state if it was not allready in order to send the data to the
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destination.
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@ -289,7 +293,7 @@ can build simple server applications with it.
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information when it prerolled the pipeline.
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When a client performs a PAUSE request, the destination UDP ports are removed
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from the GstRTSPMediaStream object and the GstRTSPMedia object is set to PAUSED
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from the GstRTSPStream object and the GstRTSPMedia object is set to PAUSED
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if no other destinations are configured anymore.
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@ -317,7 +321,7 @@ can build simple server applications with it.
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Various ways exist to detect activity from a client:
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- RTSP keepalive requests. When a client is receiving RTP data, the RTSP TCP
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connection is largely unused. It is the client responsability to
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connection is largely unused. It is the client's responsability to
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periodically send keep-alive requests over the TCP channel.
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Whenever a keep-alive request is received by the server (any request that
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receiving RTCP exactly for this reason.
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If there was no activity in a particular session for a long time (by default 60
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seconds), the sessionpool will destroy the session along with all related
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objects and media as if a TEARDOWN happened from the client.
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seconds), the application should remove the session from the pool. For this,
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the application should periodically (say every 2 seconds) check if no sessions
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expired and call gst_rtsp_session_pool_cleanup() to remove them.
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When a session is removed from the sessionpool and its last reference is
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unreffef, all related objects and media are destroyed as if a TEARDOWN happened
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from the client.
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* TEARDOWN
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A TEARDOWN request will first location the GstRTSPSessionMedia of the URL. It
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A TEARDOWN request will first locate the GstRTSPSessionMedia of the URL. It
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will then remove all transports from the streams, making sure that streaming
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stops to the client. It will then remove the GstRTSPSessionMedia and
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GstRTSPSessionStream structures. Finally the GstRTSPSession is released back
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stops to the clients. It will then remove the GstRTSPSessionMedia and
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GstRTSPStreamTransport objects. Finally the GstRTSPSession is released back
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into the pool.
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When there are no more references to the GstRTSPMedia, the media pipeline is
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shut down and destroyed.
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shut down (with _unprepare) and destroyed. This will then also destroy the
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GstRTSPStream objects.
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Objects
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-------
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GstRTSPServer
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- Toplevel object listening for connections and creating new
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GstRTSPClient objects
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GstRTSPClient
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- Handle RTSP Requests from connected clients. All other objects
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are called by this object.
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GstRTSPClientState
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- Helper structure contaning the current state of the request
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handled by the client.
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GstRTSPAuth
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- Hooks for checking authorizations, all client activity will call this
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object with the GstRTSPClientState structure. By default it supports
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basic authentication.
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GstRTSPMediaMapping
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- Maps a url to a GstRTSPMediaFactory implementation. The default
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implementation uses a simple hashtable to map a url to a factory.
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GstRTSPMediaFactory
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- Creates and caches GstRTSPMedia objects. The default implementation
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can create GstRTSPMedia objects based on gst-launch syntax.
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GstRTSPMediaFactoryURI
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- Specialized GstRTSPMediaFactory that can stream the content of any
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URI.
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GstRTSPMedia
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- The object that contains the media pipeline and various GstRTSPStream
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objects that produce RTP packets
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GstRTSPStream
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- Manages the elements to stream a stream of a GstRTSPMedia to one or
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more GstRTSPStreamTransports.
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GstRTSPSessionPool
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- Creates and manages GstRTSPSession objects identified by an id.
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GstRTSPSession
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- An object containing the various GstRTSPSessionMedia objects managed
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by this session.
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GstRTSPSessionMedia
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- The state of a GstRTSPMedia and the configuration of a GstRTSPStream
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objects. The configuration for the GstRTSPStream is stored in
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GstRTSPStreamTransport objects.
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GstRTSPStreamTransport
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- Configuration of how a GstRTSPStream is send to a particular client. It
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contains the transport that was negotiated with the client in the SETUP
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request.
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