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Streaming, RTP, RTSP ITEM, 26feb02, Leif Arne Rønningen. Streaming from a Streaming Server to a Media player. ITEM, 1nov00 Leif Arne Rønningen. Media Player. The Media Player shown is a plug-in to the browser (running native code) or a stand-alone application, and provides the following:

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media player
Media Player
  • The Media Player shown is a plug-in to the browser (running native code) or a stand-alone application, and provides the following:
    • Decompression
    • Jitter removal
    • Error correction
    • GUI – Graphical User Interface
best effort quality of service qos
Best-effort Quality of Service - QoS
  • Internet today, best-effort delivery service
    • No guarantee of
      • End-to-end delay
      • Delay jitter
      • Packet loss
      • Packet sequence
    • No traffic control
    • No admission control
rtp real time transport protocol
RTP - Real-time Transport Protocol
  • One-way streaming, unicast or multicast of audio and video in general
  • The media stream is sent as chunks of data, put into RTP packets
  • Each RTP packet header includes stream identifier, time stamp and sequence number (error correction)
  • On top of UDP/IP
  • Application and transport layer
  • Does not provide Quality of service guarantee
rtcp rtp control protocol
RTCP – RTP Control Protocol
  • Used with RTP to monitor the Quality of Service
  • Feedback information can be used for adaptive control of senders’ output data rates (adaptive scaling of service profile and level)
  • On top of UDP/IP
  • Does not provide Quality of Service guarantee
rtsp real time streaming protocol
RTSP - Real-time Streaming Protocol
  • Application-level protocol for control over the delivery of data with real-time properties
  • Media on-demand control, player-server interaction
  • Requests and Responses, not memoryless, ’HTTP-friendly’, supports most HTTP features + new
  • RTP used for the actual delivery of data (sound, video)
  • On top of UDP/IP or TCP/IP
  • Does not provide Quality of Service guarantee
slide8

RTSP, example

HTTP GET

Web

Browser

Web

Server

Descriptionfile

SETUP

Media

Player

Media

Server

PLAY

Media stream

PAUSE

TEARDOWN

slide9

RTSP, description file

<title>Twister/title>

<session>

<group language=en lipsync>

<switch>

<track type=audio

e=”PCMU/8000/1”

src= ”rtsp://audio.example.com/twister/

audio.en/lofi”>

<track type=audio

e=”DVI4/16000/2” pt=”90 DVI4/8000/1”

scr=”rtsp://audio.example.com/twister/

audio.en/hifi”>

</switch>

<track type=”video/jpeg”

scr=”rtsp://video.example.com/twister/video”>

</group>

</session>

slide10

Explanation

The RTSP Content Markup Language document can be defined using an XML DTD (Document Type Definition), and is HTML-like. Most of it is self-explanatory. The ’group’ includes two audio tracks and a video track, and the ’group’ tag includes the language parameter (en =English) and a requirement that the sound shall be lip-synchronised with the video. The ’swich’ tag indicates that we can swich between two sound tracks. The coding schemes for the audio are given by the parameters ’e’ and ’pt’. To locate resources, RTSP defines a variant of URL, see ’src’. The parameter ’lofi’ indicates ’low fidelity’ sound. The RTSP URL may include a port number.

slide11

RTSP, player-server interaction

Player: SETUP rtsp://audio.example.com/twister/audio RTSP/1.0

Cseq: 1

Transport: rtp/udp; compression; port=3056; mode=PLAY

Server: RTSP/1.0 200 OK

Cseq: 1

Date: 23 Jan 2001 17:45:05 GMT

Session: 42311234

Transport: rtp/udp; compression; port=3056; mode=PLAY

P: PLAY rtsp://audio.example.com/twister/audio.en/lofi RTSP/1.0

Cseq: 2 Session: 42311234

Range: npt=0-

S: RTSP/1.0 200 OK

Cseq: 3

Date: 23 Jan 2001 17:46:05 GMT

Range: npt=0-

slide12

RTSP, player-server interaction

P: PAUSE rtsp://audio.example.com/twister/audio.en/lofi RTSP/1.0

Cseq: 4

Session: 42311234

Range: npt=37

S: RTSP/1.0 200 OK

Cseq: 4

Date: 23 Jan 2001 17:47:05 GMT

P: TEARDOWN rtsp://audio.example.com/twister/audio.en/

lofi RTSP/1.0

Cseq: 10

Session: 42311234

S: RTSP/1.0 200 OK

Cseq: 10

slide13

Explanation

The request-response interaction between Player and Server are HTTP-like, but not memoryless. A setup has to be performed before data transfer can take place. The SETUP method is followed by the RTSP URL (universal resource locator). Cseq is a sequence number that uniquely identifies each request-response. The session number identifies the setup session. The RTP protocol shall be used, over UDP. The ’npt’ parameter indicates the ’normal play time’ in seconds. The rest should be self-explanatory.

quicktime streaming media
QuickTime streaming media
  • QuickTime
    • Browser plug-in, or stand-alone QuickTime Player
    • Retrieve streams from QuckTime Streaming Server
    • Handles multimedia components like

video, sound, animation, graphics, text, music, 360-degree virtual reality (VR) scenes

stored in every major format

    • Timecode tracks
    • RTP and RTSP application protocols
    • See www.apple.com/quicktime/ for more details
  • QuckTime demo

rtsp://129.241.26.182/stud/arne/ice_age_hint.mov

rtsp media player server message sequence chart
RTSP Media Player-Server, Message Sequence Chart

User

Interface

RTSP

Player

RTSP

Server

OpenURL

SETUP

response1

PLAY

Activate

RTP

Activate

RTP

response2

audio

PAUSE

response3

Quit

TEARDOWN

response10

media player state transition diagram
Media Player State-transition diagram

y

x

Wait S2

O

O

Passive

Response2 / Activate RTP

OpenURL / SETUP

Play,

RTP

Wait S1

O

O

response1

/ PAUSE

Wait S3

Wait UI1

O

O

response3

/ PLAY

z

y

media player state transition diagram17
Media Player State-transition diagram

z

Wait UI2

O

Quit / TEARDOWN

Wait S10

O

response10

Transition:

message in / message out, task

x

O – other message

– continue

z

state machine implementation
State Machine Implementation

RTP

State

descripton

table

Task or method

Queue

State

Interpreter

Message

in

Message

out

State

Software

Process (entity)

Note: RTP could be implementet as a

separate entity, not as a task

table

state interpreter behaviour
State Interpreter behaviour
  • waituntil (at least one message in queue)
  • get message from queue
  • check message name
  • read present state
  • read state table (state, message in)
  • set next state
  • send out message (state, message in)
  • activate task or function
state description table
State Description Table

State message in next state message out task/function

Wait UI2 Quit Wait S10 TEARDOWN

,,, ,,,

,,, ,,,

Wait S2 response2 Play, RTP activate RTP

timeouts retry counters
Timeouts, retry-counters

Timer

RTSP

Player

OpenURL(N=3)

SETUP

Set-timer(2, N)

(response1 is lost)

2 sec.

Timeout(2,N)

SETUP

Set-timer(2, N)

(response1 delayed)

2 sec.

Timeout(2,N)

Countdown:

If N=0 then

begin N:=3;

State:=’Passive’

end else N:=N-1;

response1

extended state machine
Extended state machine

State

descripton

table

xyz

xyz

Tasks or methods

Queue

State

Interpreter

Message

in

Message

out

State,

Variable N

Next state

dependent on

value of N

software

table

Note: The Timer can be implemented

as a task or as a separate entity

other streaming media systems
Other streaming media systems
  • RealPlayer
  • Sun Java Media Framework
  • Microsoft Streaming Media
  • MPEG-21 (coming)
  • Other
qos guarantee
QoS guarantee
  • Packets have to be classified in different traffic classes
  • It is desireable to minimise interference between traffic flows
  • Resources like link capacity, storage and processing units should be utilised efficiently
  • Call admission control is needed. Admission requestes from flows have to include QoS requirements