Real-Time Streaming Protocol
| application | RTSP | ||||
| transport | UDP | TCP | |||
| Internet | IP ( IPv4 , IPv6 ) | ||||
| Network access | Ethernet |
Token bus |
Token ring |
FDDI | ... |
The Real-Time Streaming Protocol ( RTSP ) is a network protocol for controlling the continuous transmission of audiovisual data ( streams ) or software over IP -based networks . It controls the session between recipient and server. RTSP is a text-based protocol and is similar in structure and behavior to HTTP . The standard communication takes place via port 554 (alternatively also 8554) via UDP or TCP . The protocol was developed by the IETF MMUSIC Group and standardized in RFC 2326 in 1998 .
Overview
While in practice the Real-Time Transport Protocol (RTP, RFC 3550 , July 2003 ) is mostly used to transmit data in real time (RTSP is protocol-independent), the RTSP function is mainly to control the data streams; No user data is transmitted via RTSP itself, which is why RTSP is sometimes referred to as "network remote control". The transmission is controlled by the RealTime Control Protocol (RTCP).
RTSP is for multimedia data streams what HTTP is for HTML documents; In contrast to HTTP, however, RTSP knows states and is bidirectional, which means that both the client and the server can send requests. Otherwise, in RTSP as in HTTP, the messages are divided into request (to initialize a session) and response (to answer the request with a status message).
The elements of a multimedia presentation are defined, aggregated and time-synchronized by the markup language Synchronized Multimedia Integration Language (SMIL; SMIL 1.0 from 1997, SMIL 2.0 from 2001).
RTSP-capable streaming servers include the Helix Server and the QuickTime Streaming Server (since 1999 ).
A freely available implementation ( GPL or LGPL ) is the ffserver of the FFmpeg project, the further development of which was dropped in the context of this project.
Another free implementation is the LIVE555 used in VLC .
Since the takeover of Softricity Inc. , the software company Microsoft has also been using RTSP in its software distribution system App-V (formerly SoftGrid) to transfer applications from the server to the client in such a way that the client can use the software as soon as possible. even if it is not yet fully downloaded.
terminology
A large number of terms are used when using the RTSP analogous to http.
- Aggregate Control
- The media server uses a time axis to control multiple streams. To control the audio and video signals together, the client can send a command for both.
- Conference / Conference
- a multi-user multimedia presentation, where “multi-user” means at least two participants. These can also be other IT systems.
- Client
- The client at RTSP continuously receives information from the server.
- Connection
- A network connection with the aim of exchanging information.
- Container file
- A file that provides the information for media streams.
- Continuous media
- In contrast to data packets, the audio and video signals must be played back on the client in the same chronological order. This is critical for real-time transmission, less of a problem when playing back recordings.
- Entity
- Is the sum of the transport information that is transferred between client (s) and servers.
- Media initialization
- Contains the data type / codec (H.264). Also z. B. Time information, color signals (FBAS), etc. The client needs the information for correct playback of the media stream.
- Media server
- The server provides one or more media streams. Different media streams can be combined into one presentation. A media server can be operated on the web server or on a backend server.
- Media Server Indirection
- “Redirection” of a client to another media server.
- (Media) stream
- Is an instance, for example an audio stream or a video stream, as well as virtual collaboration (whiteboard or application).
- Message
- Command to establish a connection.
- Participant / participant
- Participant in a conference. A participant can also use an IT system, e.g. B. a media recorder or video proxy.
- Response
- An RTSP request typically contains a mechanism for continuous transmission (Media Stream SETUP, the stream is started with PLAY or RECORD, ended with TEARDOWN).
Web links
Individual evidence
- ↑ FFmpeg. In: ffmpeg.org. Retrieved September 8, 2016 .
- ↑ https://wiki.videolan.org/Live555/