RTSP support

[gavv]

Implement RTSP support and use it for session negotiation (#34).

Ideally, both RTSP/1 and RTSP/2 should be supported.

RTSP support will consist of the following:

• implement RTSP handler for roc_ctl (Implement roc_ctl module #214)
• allow sender and receiver in the API tools to act as a server or a client (Refine roc_sender/roc_receiver API #263)
• if sender or receiver is a server, support serving an RTSP endpoint
• if sender or receiver is a client, support connecting to an RTSP endpoint
• implement session negotiation: session parameters should be passed via RTSP; source and repair endpoints should be allocated dynamically and also passed via RTSP
• support RTSP endpoints in tools
• support RTSP endpoints in API
• support RTSP endpoints in PulseAudio modules

[gavv]

Features

Initially, we will implement a minimal RTSP client and server supporting only live sessions (i.e. no seeking, scaling, ranges, and pipelining).

The requirements to it are described here: https://tools.ietf.org/html/rfc2326#page-85

We should implement at least these methods:

• OPTIONS
• DESCRIBE
• ANNOUNCE
• SETUP
• TEARDOWN
• RECORD
• PLAY

In the initial implementation we should be able to parse, or generate, or both (depending on the field) the following header fields:

• Accept
• Allow
• Content-Base
• Content-Encoding
• Content-Length
• Content-Type
• CSeq
• Connection
• Require
• RTP-Info
• Session
• Server
• Transport
• Unsupported
• User-Agent

Ideally, we should also support (maybe later):

• pausing (client and server)
• redirects, including REDIRECT method and Location/Content-Location fields (on client)
• retries, including Retry-After field (on client and server)
• If-Match/If-Modified-Since/Last-Modified/etag (at least on server)

We will implement a single content encoding: application/sdp.

We will implement at least RTP/AVP transport, and probably also RTP/AVP/TCP (interleaved) transport.

We will implement at least "rtsp://" scheme, and probably also "rtspu://" scheme.

The initial implementation will not provide encryption.

[gavv]

Methods usage

Sender connects to receiver (sender is client, receiver is server):

• C->S ANNOUNCE
• C->S SETUP
• C->S RECORD
• C->S TEARDOWN

Receiver connects to sender (receiver is client, sender is server):

• C->S DESCRIBE
• C->S SETUP
• C->S PLAY
• C->S TEARDOWN

[gavv]

Negotiated parameters

• addresses
• rtpmap (dynamic payload types)
• fssi (FEC-scheme specific information)