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140 lines
6.3 KiB
Plaintext
140 lines
6.3 KiB
Plaintext
Written by: Sascha Volkenandt <sascha@akv-soft.de>
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Project's homepage: http://www.magoa.net/linux/
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Version: 0.0.3
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Description:
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------------
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I call this protocol "VTP", the Video Transfer Protocol. I hope that's not
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already claimed by someone ;).
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This Protocol was created for Video Transfers over a Network. It is a text-
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based protocol like the FTP, and is used by a client to communicate with a
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server providing different types of video data, such as live streams,
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recordings or disc media. The basic communication consists of short text
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commands sent by the client, answered by numerical codes accompanied by
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human-readable messages. All messages should be finished by a full CR/LF
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line-ending, which should preferably written as "\015\012", as this is fully
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platform-independent. Nevertheless, a client or (especially) a server should
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also act on "\n" line-endings. The MPEG data is being transmitted over a
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separate data connection.
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TODO:
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- PORT behaviour changed
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- TUNE syntax changed
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- connection IDs
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- new command PLAY
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Response Code Summary
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Code Meaning
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220 Last command ok / connection ready
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221 Service is closing the connection afterwards
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500 The command was not recognized
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501 The parameters couldn't be interpreted correctly
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550 Action not taken, for various reason
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551 Action not taken, a subsequent connection was unsuccessful
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560 Live-Stream not available currently [changed in 0.0.3]
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561 Capability not known [new in 0.0.2]
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562 Pid currently not available [new in 0.0.3]
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563 Stream not available currently [new in 0.0.3]
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Command Reference
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Command: Connect to VTP Server
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Responses: 220 - The server is ready
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Description: Upon connection to the server (which usually listens at port
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2004), the first thing the client has to expect is a welcome message with
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the "220" response code. The client may now send a CAPS command, to tell
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the server it's capabilities.
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Command: CAPS <Capability>
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Responses: 220 - This capability is known and will be used from now on.
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561 - This capability is unknown, try anotherone
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Description: This command tells the server to serve media data in a specific
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format, like "PES" (for MPEG2-PES) or "TS" (for MPEG2-TS). A client can
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do several CAPS commands until the server accepts one. So a client should
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try all formats it can handle, descending from the most preffered one. If
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no such command is sent, streaming is defaulted to PES.
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Capabilities currently used:
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TS Transport Stream (all PIDs belonging to a channel)
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TSPIDS Only in conjunction with TS: Stream PIDs separately upon request
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(this enables the ADDP/DELP commands)
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PES Program Elementary stream (Video and primary Audio stream)
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[new in 0.0.2,updated in 0.0.3]
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Command: PROV <Priority> <Media>
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Responses: 220 - Media available for receive
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501 - The parameters were incorrect
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550 - The media couldn't be identified
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560 - This server can currently not serve that media
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Description: With this command, the server is asked if the given media can
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be received. The Priority is a number between 0 and 100 (in case a media
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can not be received by an unlimited number of clients, the server shall
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grant higher priorities before lower ones, and it shall also quit streams
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with lower permissions if a higher one is requested), or -1 to ask the
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server if this media is available at all.
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The Media is a string defining the wanted media type. This is currently for
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free use, it could for example carry a VDR unique channel id, to specify
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a TV channel.
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Command: PORT <Id> <Address and Port>
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Responses: 220 - The data connection was opened
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501 - The parameter list was wrong
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551 - The data connection was refused by the client or timed out
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Description: The PORT command tells the server the target of a following
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media transmission. The parameter Id specifies an index which is used to
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establish multiple data connections over one control connection. It is used
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later in the ABRT command to close a specific data connection. The second
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parameter argument has six comma-separated fields, of which the first four
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represent the target IP address, in the byte-order as the dot-notation
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would be printed. The last two fields represent the target port, with the
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high-byte first. To calculate the actual values, you could use the
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following:
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Field(5) = (RealPort & 0xFF00) shr 8
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Field(6) = RealPort & 0xFF
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Reversed:
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RealPort = (Field(5) shl 8) + Field(6)
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After receiving the port command, the data connection is opened but no data
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is transferred, yet.
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Id's currently used:
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0 Data connection for live streams
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1 Data connection for saved streams
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[changed in 0.0.3]
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Command: TUNE <Priority> <Media>
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Responses: 220 - Data connection was opened successfully
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550 - The media couldn't be identified
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560 - The live stream is unavailable
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Description: This command tells the media server to start the transfer over a
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connection to a remote target established by the PORT command before.
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Please look at the PROV command for the meaning of the parameters. The
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server begins to send MPEG data. After the transfer has been started, the
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response code "220" is sent.
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Command: ADDP <Pid>
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Responses: 220 - The requested Pid is transferring
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560 - The requested Pid is not available currently
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Description: This tells the server to start the transfer of a specific Pid
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over a data connection established by the PORT command before.
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Command: DELP <Pid>
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Responses: 220 - The requested Pid is transferring
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560 - The requested Pid was not transferring
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Description: This tells the server to stop the transfer of a specific Pid
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enabled by DELP before.
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Command: ABRT <Id>
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Responses: 220 - Data connection closed
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Description: This one should be sent before requesting another media or when
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a media isn't needed anymore. It terminates the data connection previously
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opened by PORT.
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Command: QUIT
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Responses: 221 - Connection is being closed afterwards
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Description: This commands terminates the client connection.
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