RTSP（Real Time Streaming Protocol）学习笔记 -- RFC2326

Real Time Streaming Protocol (RTSP) 

RTSP是用在娱乐或通讯中控制流媒体服务器的网络协议，它可以创建和控制两个端点之间的会话. Client发出一些命令来控制media streaming。例如：play, record and pause.

RTSP is a text-based protocol.
Lines are terminated by CRLF.
Text-based protocols make it easier to add optional parameters in a self-describing manner.

1. RTSP URL

rtsp_URL = ( "rtsp:" | "rtspu:" )"//" host [ ":" port ] [ abs_path ]

host = <A legal Internet host domain name of IP address

port = *DIGIT 

example: rtsp://media.example.com:554/twister/audiotrack

2. RTSP Message

The message type, message headers and message body reuse the HTTP protocol.

3. Method:

1). OPTIONS

　　An OPTIONS request returns the request types the server will accept.

2). DESCRIBE

　　A DESCRIBE request includes an RTSP URL (rtsp://...), and the type of reply data that can be handled. This reply includes the presentation description, typically in Session Description Protocol (SDP) format.

3). SETUP

　　Causes the server to allocate resources for a stream and start an RTSP session.

4). PLAY & RECORD

　　Starts data transmission on a stream allocated via SETUP.

5). PAUSE

　　Temporarily halts a stream without freeing server resources.

6). RECORD

　　Same as PLAY

7). ANNOUNCE

　　When sent from client to server, ANNOUNCE posts the description of a presentation or media object identified by the request URL to a

server. When sent from server to client, ANNOUNCE updates the session description in real-time.

8). TEARDOWN

　　Frees resources associated with the stream. The RTSP session ceases to exist on the server.

9). GET_PARAMETER

　　The GET_PARAMETER request retrieves the value of a parameter of a presentation or stream specified in the URI.

10). SET_PARAMETER

　　This method requests to set the value of a parameter for a presentation or stream specified by the URI.

11). REDIRECT

　　 A REDIRECT request informs the client that it must connect to another server location.

12). Embedded (Interleaved) Binary Data

某些防火墙设计和其他情况可能迫使服务器交错RTSP方法和流数据。该交错通常应避免使用，除非必要的，因为它的复杂性使得客户端和服务器的操作会增加额外的开销。

　　如果RTSP通过TCP进行，才应使用交错的二进制数据。

4. 一些定义原RFC直接copy过来放这里。

6 Request

A request message from a client to a server or vice versa includes,
   within the first line of that message, the method to be applied to
   the resource, the identifier of the resource, and the protocol
   version in use.

Request      =       Request-Line          ; Section 6.1
                    *(      general-header        ; Section 5
                    |       request-header        ; Section 6.2
                    |       entity-header )       ; Section 8.1
                            CRLF
                            [ message-body ]      ; Section 4.3

6.1 Request Line

Request-Line = Method SP Request-URI SP RTSP-Version CRLF

Method         =         "DESCRIBE"              ; Section 10.2
                  |         "ANNOUNCE"              ; Section 10.3
                  |         "GET_PARAMETER"         ; Section 10.8
                  |         "OPTIONS"               ; Section 10.1
                  |         "PAUSE"                 ; Section 10.6
                  |         "PLAY"                  ; Section 10.5
                  |         "RECORD"                ; Section 10.11
                  |         "REDIRECT"              ; Section 10.10
                  |         "SETUP"                 ; Section 10.4
                  |         "SET_PARAMETER"         ; Section 10.9
                  |         "TEARDOWN"              ; Section 10.7
                  |         extension-method

extension-method = token

Request-URI = "*" | absolute_URI

RTSP-Version = "RTSP" "/" 1*DIGIT "." 1*DIGIT

6.2 Request Header Fields

request-header  =          Accept                   ; Section 12.1
                  |          Accept-Encoding          ; Section 12.2
                  |          Accept-Language          ; Section 12.3
                  |          Authorization            ; Section 12.5
                  |          From                     ; Section 12.20
                  |          If-Modified-Since        ; Section 12.23
                  |          Range                    ; Section 12.29
                  |          Referer                  ; Section 12.30
                  |          User-Agent               ; Section 12.41

Note that in contrast to HTTP/1.1 [2], RTSP requests always contain
   the absolute URL (that is, including the scheme, host and port)
   rather than just the absolute path.

HTTP/1.1 requires servers to understand the absolute URL, but
     clients are supposed to use the Host request header. This is purely
     needed for backward-compatibility with HTTP/1.0 servers, a
     consideration that does not apply to RTSP.

The asterisk "*" in the Request-URI means that the request does not
   apply to a particular resource, but to the server itself, and is only
   allowed when the method used does not necessarily apply to a
   resource.  One example would be:

OPTIONS * RTSP/1.0

7 Response

[H6] applies except that HTTP-Version is replaced by RTSP-Version.
   Also, RTSP defines additional status codes and does not define some
   HTTP codes. The valid response codes and the methods they can be used
   with are defined in Table 1.

After receiving and interpreting a request message, the recipient
   responds with an RTSP response message.

Response    =     Status-Line         ; Section 7.1
                 *(    general-header      ; Section 5
                 |     response-header     ; Section 7.1.2
                 |     entity-header )     ; Section 8.1
                       CRLF
                       [ message-body ]    ; Section 4.3

7.1 Status-Line

The first line of a Response message is the Status-Line, consisting
   of the protocol version followed by a numeric status code, and the
   textual phrase associated with the status code, with each element
   separated by SP characters. No CR or LF is allowed except in the
   final CRLF sequence.

Status-Line =   RTSP-Version SP Status-Code SP Reason-Phrase CRLF

7.1.1 Status Code and Reason Phrase

The Status-Code element is a 3-digit integer result code of the
   attempt to understand and satisfy the request. These codes are fully
   defined in Section 11. The Reason-Phrase is intended to give a short
   textual description of the Status-Code. The Status-Code is intended
   for use by automata and the Reason-Phrase is intended for the human
   user. The client is not required to examine or display the Reason-
   Phrase.

The first digit of the Status-Code defines the class of response. The
   last two digits do not have any categorization role. There are 5
   values for the first digit:

* 1xx: Informational - Request received, continuing process
     * 2xx: Success - The action was successfully received, understood,
       and accepted
     * 3xx: Redirection - Further action must be taken in order to
       complete the request
     * 4xx: Client Error - The request contains bad syntax or cannot be
       fulfilled
     * 5xx: Server Error - The server failed to fulfill an apparently
       valid request

The individual values of the numeric status codes defined for
   RTSP/1.0, and an example set of corresponding Reason-Phrase's, are
   presented below. The reason phrases listed here are only recommended
   - they may be replaced by local equivalents without affecting the
   protocol. Note that RTSP adopts most HTTP/1.1 [2] status codes and
   adds RTSP-specific status codes starting at x50 to avoid conflicts
   with newly defined HTTP status codes.

Status-Code  =     "100"      ; Continue
                |     "200"      ; OK
                |     "201"      ; Created
                |     "250"      ; Low on Storage Space
                |     "300"      ; Multiple Choices
                |     "301"      ; Moved Permanently
                |     "302"      ; Moved Temporarily
                |     "303"      ; See Other
                |     "304"      ; Not Modified
                |     "305"      ; Use Proxy
                |     "400"      ; Bad Request
                |     "401"      ; Unauthorized
                |     "402"      ; Payment Required
                |     "403"      ; Forbidden
                |     "404"      ; Not Found
                |     "405"      ; Method Not Allowed
                |     "406"      ; Not Acceptable
                |     "407"      ; Proxy Authentication Required
                |     "408"      ; Request Time-out
                |     "410"      ; Gone
                |     "411"      ; Length Required
                |     "412"      ; Precondition Failed
                |     "413"      ; Request Entity Too Large
                |     "414"      ; Request-URI Too Large
                |     "415"      ; Unsupported Media Type
                |     "451"      ; Parameter Not Understood
                |     "452"      ; Conference Not Found
                |     "453"      ; Not Enough Bandwidth
                |     "454"      ; Session Not Found
                |     "455"      ; Method Not Valid in This State
                |     "456"      ; Header Field Not Valid for Resource
                |     "457"      ; Invalid Range
                |     "458"      ; Parameter Is Read-Only
                |     "459"      ; Aggregate operation not allowed
                |     "460"      ; Only aggregate operation allowed
                |     "461"      ; Unsupported transport
                |     "462"      ; Destination unreachable
                |     "500"      ; Internal Server Error
                |     "501"      ; Not Implemented
                |     "502"      ; Bad Gateway
                |     "503"      ; Service Unavailable
                |     "504"      ; Gateway Time-out
                |     "505"      ; RTSP Version not supported
                |     "551"      ; Option not supported
                |     extension-code

extension-code  =     3DIGIT

Reason-Phrase  =     *<TEXT, excluding CR, LF>

RTSP status codes are extensible. RTSP applications are not required
   to understand the meaning of all registered status codes, though such
   understanding is obviously desirable. However, applications MUST
   understand the class of any status code, as indicated by the first
   digit, and treat any unrecognized response as being equivalent to the
   x00 status code of that class, with the exception that an
   unrecognized response MUST NOT be cached. For example, if an
   unrecognized status code of 431 is received by the client, it can
   safely assume that there was something wrong with its request and
   treat the response as if it had received a 400 status code. In such
   cases, user agents SHOULD present to the user the entity returned
   with the response, since that entity is likely to include human-
   readable information which will explain the unusual status.

Code           reason

100            Continue                         all

200            OK                               all
   201            Created                          RECORD
   250            Low on Storage Space             RECORD

300            Multiple Choices                 all
   301            Moved Permanently                all
   302            Moved Temporarily                all
   303            See Other                        all
   305            Use Proxy                        all
   400            Bad Request                      all
   401            Unauthorized                     all
   402            Payment Required                 all
   403            Forbidden                        all
   404            Not Found                        all
   405            Method Not Allowed               all
   406            Not Acceptable                   all
   407            Proxy Authentication Required    all
   408            Request Timeout                  all
   410            Gone                             all
   411            Length Required                  all
   412            Precondition Failed              DESCRIBE, SETUP
   413            Request Entity Too Large         all
   414            Request-URI Too Long             all
   415            Unsupported Media Type           all
   451            Invalid parameter                SETUP
   452            Illegal Conference Identifier    SETUP
   453            Not Enough Bandwidth             SETUP
   454            Session Not Found                all
   455            Method Not Valid In This State   all
   456            Header Field Not Valid           all
   457            Invalid Range                    PLAY
   458            Parameter Is Read-Only           SET_PARAMETER
   459            Aggregate Operation Not Allowed  all
   460            Only Aggregate Operation Allowed all
   461            Unsupported Transport            all
   462            Destination Unreachable          all

500            Internal Server Error            all
   501            Not Implemented                  all
   502            Bad Gateway                      all
   503            Service Unavailable              all
   504            Gateway Timeout                  all
   505            RTSP Version Not Supported       all
   551            Option not support               all

Table 1: Status codes and their usage with RTSP methods

7.1.2 Response Header Fields

The response-header fields allow the request recipient to pass
   additional information about the response which cannot be placed in
   the Status-Line. These header fields give information about the
   server and about further access to the resource identified by the
   Request-URI.

response-header  =     Location             ; Section 12.25
                    |     Proxy-Authenticate   ; Section 12.26
                    |     Public               ; Section 12.28
                    |     Retry-After          ; Section 12.31
                    |     Server               ; Section 12.36
                    |     Vary                 ; Section 12.42
                    |     WWW-Authenticate     ; Section 12.44

Response-header field names can be extended reliably only in
   combination with a change in the protocol version. However, new or
   experimental header fields MAY be given the semantics of response-
   header fields if all parties in the communication recognize them to
   be response-header fields. Unrecognized header fields are treated as
   entity-header fields.

8 Entity

Request and Response messages MAY transfer an entity if not otherwise
   restricted by the request method or response status code. An entity
   consists of entity-header fields and an entity-body, although some
   responses will only include the entity-headers.

In this section, both sender and recipient refer to either the client
   or the server, depending on who sends and who receives the entity.

8.1 Entity Header Fields

Entity-header fields define optional metainformation about the
   entity-body or, if no body is present, about the resource identified
   by the request.

entity-header       =    Allow               ; Section 12.4
                         |    Content-Base        ; Section 12.11
                         |    Content-Encoding    ; Section 12.12
                         |    Content-Language    ; Section 12.13
                         |    Content-Length      ; Section 12.14
                         |    Content-Location    ; Section 12.15
                         |    Content-Type        ; Section 12.16
                         |    Expires             ; Section 12.19
                         |    Last-Modified       ; Section 12.24
                         |    extension-header
     extension-header    =    message-header

The extension-header mechanism allows additional entity-header fields
   to be defined without changing the protocol, but these fields cannot
   be assumed to be recognizable by the recipient. Unrecognized header
   fields SHOULD be ignored by the recipient and forwarded by proxies.