Some Background about 3GPP SA4’s RTSP extensions

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Some Background about 3GPP SA4’s

RTSP extensions

Thorsten Lohmar

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© Ericsson AB 2008 EDD/XR/V Thorsten Lohmar 2008-05-192

This slides give some further motivation and background around 3GPP SA4’s extensions to RTSP 1.0. These slides are not endorsed by 3GPP SA4.

S4-080090 contains the Liaison Statement “about on-going work on RTSP 2.0 and request for information on RTSP extensions”


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SA4’s extension to RTSP

SA4’s Packet Switched Streaming Specification (PSS) (TS 26.234) is based on RTSP 1.0

SA4 has “profiled” RTSP 1.0 for Mobile Streaming usage

SA4 has defined several extensions to RTSP 1.0– Liaison Statement about extensions

RTSP 2.0 will be discussed in 3GPP when it becomes an RFC


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Fast Content Switching and Startup Motivation:

– Switch content of a streaming session but re-using RTSP & RTP sessions A set of content is offered to the user Typical same number of media flows (eg. A &V) per content Same codecs and resolution for the set of content Example: Mobile TV with Fast Channel Switching

– Switch between streams of same content Example: languages or camera views in a streaming session

without interrupting the whole streaming session A content is provided in multiple languages or with multiple

camera views The user selects a different language or camera view during the

running session– Pipelined Start-up (already adopted by RTSP 2.0)

Goal: Minimize Round-Trips to get new content played Reference: TS 26.234 (Chapter 5.5 and Annex M) Internet-Draft under preparation


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Quality of Experience Reporting

Motivation: Sending streaming specific information back

– initial buffering duration– re-buffering events of streamed media– Packet loss bursts– Frame rate deviation– Channel switch events and duration– …

Reference: TS 26.234 (Chapter 11 and Chapter 5.3 for the extra RTSP header definitions)


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FLUTE session setup with RTSP

Motivation (defined in TS 26.346 clause clase 7.5): – Interactive Mobile TV: Proving “Interactive Media

Documents” (IMD, cf. OMA BCAST) inband with the PSS unicast session

– Alignment with Broadcast (MBMS / DVB) to “simplify” hybrid service offerings

Thus, FLUTE session is established together with other RTP streaming sessions to provide complementary information/services

IMDs are small in size and are evaluated after reception


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PSS Timeshifting (Work in Progress) Motivation: Mobile TV and IPTV require “timeshifting”

functionality– User enters “timeshifting state” just by pausing, seeking, or

reverse playing a live session– RTSP session transits from “live” and “on-demand” timeline

(Network Timeshift)– Timeshift may increase “perceived” quality of a broadcast to

unicast handover The media playout is continued without gaps, although the

transport change and playout interruptions– Local “timeshift” considered, but likely not specified

The current Use-Cases and Working Assumptions are gathered in S4-080252


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Some Background about 3GPP SA4’s RTSP extensions

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