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 addressport = *DIGITexample: rtsp://media.example.com:554/twister/audiotrack
2. RTSP Message
The message type, message headers and message body reuse the HTTP protocol.
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。
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.