Prepared by: Date: Document: Ascom Network Testing 16 December 2009 EAB-09:042807 Rev A © Ascom (2009) All rights reserved. TEMS is a trademark of Ascom. All other trademarks are the property of their respective holders.

TEMS Investigation

Video Streaming Client – Technical Description

© Ascom (2009) Document: EAB-09:042807 Rev A

Contents

1  Introduction ................................................................ 1 

2  RTSP Support ............................................................. 1 

2.1  DESCRIBE Request ................................................................... 1 

2.2  SETUP Request .......................................................................... 1 

2.3  PLAY Request ............................................................................ 1 

2.4  TEARDOWN Request................................................................. 1 

2.5  RTSP Request Usage ................................................................ 2 

3  SDP Support ............................................................... 3 

3.1  Supported SDP Commands ...................................................... 3 

3.1.1  Session Description ..................................................................... 3 3.1.2  Time Description .......................................................................... 4 3.1.3  Media Description ........................................................................ 4 

4  Supported Video Formats ......................................... 5 

5  Supported Codecs ..................................................... 5 

5.1  Supported Audio Codecs .......................................................... 5 

5.2  Supported Video Codecs .......................................................... 5 

© Ascom (2009) Document: EAB-09:042807 Rev A 1(5)

1 Introduction This document describes the workings of the video streaming client that is part of the TEMS Investigation software.

2 RTSP Support The Real Time Streaming Protocol (RTSP) is a network control protocol for controlling streaming media servers in entertainment and communications systems. RTSP is used to establish and control media sessions between endpoints. RTSP does not transport the media itself; that is the task of another protocol called Realtime Transport Protocol (RTP).

Below are listed all RTSP requests supported by the TEMS Investigation video streaming client.

2.1 DESCRIBE Request

A DESCRIBE request includes an RTSP URL (rtsp://...) and the type of reply data that can be handled. The default port for the RTSP protocol is 554 for both UDP and TCP transports. The reply includes the presentation description, which is typically in Session Description Protocol (SDP) format (see chapter 3).

2.2 SETUP Request

A SETUP request specifies how a single media stream is to be transported. This must be done before a PLAY request is sent. The request contains the media stream URL and a transport specifier. The specifier typically includes a local port for receiving RTP data (audio or video) and another local port for RTCP data (meta information). The server reply usually confirms the chosen parameters and fills in the missing information, such as the server’s chosen ports.

2.3 PLAY Request

A PLAY request will cause one or several media streams to be played.

2.4 TEARDOWN Request

A TEARDOWN request is used to terminate the session. It stops all media streams and frees all session related data on the server.

© Ascom (2009) Document: EAB-09:042807 Rev A 2(5)

2.5 RTSP Request Usage

Depicted below is an example of how the TEMS Investigation streaming client communicates with a streaming server using RTSP requests.

Streaming Client (TEMS) Streaming Server

Describe rtsp://x.x.x.x/VideoClip.3gp

Reply with SDP (Session Description Protocol) Info

Setup rtsp://x.x.x.x/VideoClip.3gp/VideoIdentifier

Reply

Setup rtsp://x.x.x.x/VideoClip.3gp/AudioIdentifier

Reply

Play rtsp://x.x.x.x/VideoClip.3gp

Reply

RTP data with video and audio

Teardown rtsp://x.x.x.x/VideoClip.3gp

Reply

RTSP signaling between streaming client and server.

© Ascom (2009) Document: EAB-09:042807 Rev A 3(5)

3 SDP Support The Session Description Protocol (SDP) is intended for describing multimedia communication sessions for the purposes of session announcement, session invitation, and parameter negotiation. SDP does not deliver media itself but is used for negotiation of media type, format, and associated properties between client and server.

3.1 Supported SDP Commands

The syntax of SDP is designed to be extensible to allow introduction of new media types and formats. New attributes are therefore occasionally added to the standard. What SDP commands are currently supported by the TEMS Investigation video streaming client appears from the tables that follow.

An SDP session is described by a series of attribute/value pairs, one per line. Each attribute name is a single character, followed by ‘=’ and a value. Attribute names are unique only within the associated syntactic construct, i.e. only within one of “Session”, “Time”, or “Media”.

3.1.1 Session Description

Session Description Tags Supported in TEMS Investigation

Tags Optional Mandatory

v = protocol version

o = owner/session id

s = session name

u = URI of description

e = e-mail address

c = connection

b = bandwidth info

p = phone number

z = time zone

k = encryption key

a = zero or more session attributes

3.1.1.1 Session Attributes

Session Attributes Supported in TEMS Investigation

Attribute Name Description

Range Duration of streaming file

© Ascom (2009) Document: EAB-09:042807 Rev A 4(5)

3.1.2 Time Description

Time Description Tags Supported in TEMS Investigation

Tags Optional Mandatory

t = session active time

r = repeat time

3.1.3 Media Description

Media Description Tags Supported in TEMS Investigation

Tags Optional Mandatory

m = media name and transport address

a = zero or more media attributes

3.1.3.1 Media Attributes

Media Attributes Supported in TEMS Investigation

Attribute name Description

control Media identifier

framesize Size of frame

fmtp Format-specific parameters

height Height of frame

width Width of frame

rtpmap Payload type, encoding name, clock rate, etc.

© Ascom (2009) Document: EAB-09:042807 Rev A 5(5)

4 Supported Video Formats CIF (Common Intermediate Format) is a standard video format used in video conferencing. It defines the horizontal and vertical resolutions in pixels.

The following video formats are the ones currently supported by the TEMS Investigation video streaming client:

Video Formats Supported in TEMS Investigation

Format Resolution

CIF (Full CIF) 352 288

QCIF (Quarter CIF) 176 144

SQCIF (Sub Quarter CIF) 128 96

QVGA (Quarter Video Graphics Array) 320 240

5 Supported Codecs

5.1 Supported Audio Codecs

The following audio codecs are currently supported by the TEMS Investigation video streaming client:

AMR NB

AMR WB

AMR WB+

AAC

5.2 Supported Video Codecs

The following video codecs are currently supported by the TEMS Investigation video streaming client:

H.263

H.264

MPEG4