TSG-C SWG1.2 Multimedia Services 1/21 3GPP2 Evolution Workshop Multimedia Codecs and Protocols 3GPP2 TSG-C SWG1.2

TSG-C SWG1.2 Multimedia Services 2/21 Presentation Who is TSG-C SWG 1.2? Multimedia in PS Domain –Transitioning from CS to PS –IP Terminology PS Domain Challenges –IP Fragmentation –Maintain “goodput” –Jitter –“Smarter” Codecs and Packetization –Evaluation Methodology Summary

TSG-C SWG1.2 Multimedia Services 3/21 TSG-C SWG1.2 “Multimedia Services” ToR Evaluation and adoption of –Visual Codecs (Video, Image, Graphics), –Audio Codecs (synthetic and natural audio) –Audio/visual synchronization methods Evaluation and adoption of complementary protocols –RTSP/SDP, RTP/RTCP, to support real-time, near real-time and interactive multimedia services Development of fileformats to support –over the air transmission for streaming, pseudo-streaming, downloading –associated methods for content protection

TSG-C SWG1.2 Multimedia Services 4/21 Multimedia in PS Domain Transitioning from CS to PS –Dedicated channels  Shared channels –User expectation  Similar or Higher –Application Level Framing (ALF) in IP –Requires special considerations for wireless hops Codec and transport related challenges –IP fragmentation –Jitter in packet arrival –Codecs’ view of QoS: –Greater need for error resiliency and concealment –etc.

TSG-C SWG1.2 Multimedia Services 5/21 IP Terminology ADU – Application Data Unit –Independently decodable data; minimum unit of error recovery –e.g. a vocoder frame, a video slice, … SDU – Service Data Unit –One or more ADUs, including required headers for transmission MTU – Maximum (size of a) Transmission Unit, in octets –e.g octets on an Ethernet hop, 576 octets on PPP, … PDU – Protocol Data Unit –In this context, we consider physical layer frames –payload size in one physical layer frame –Not including MAC, CRC and tail bits overhead Fragmentation and Re-assembly –1 SDU  n PDU mapping, when SDU exceeds MTU on a given hop Observation: Significant fragmentation over cdma2000® hops

TSG-C SWG1.2 Multimedia Services 6/21 IP Fragmentation

TSG-C SWG1.2 Multimedia Services 7/21 “Goodput” above RTP From RFC2736, Best Current Practice for RTP payload design, –… relying on IP fragmentation is a bad design strategy as it significantly increases the effective loss rate of a network and decreases goodput –… if one fragment is lost, the remaining fragments (which have used up bottleneck bandwidth) will then need to be discarded by the receiver Pick ADU/SDU sizes not to exceed PDU sizes Do not concatenate SDUs (use stuffing bits)

TSG-C SWG1.2 Multimedia Services 8/21 IP Fragmentation – Optimal ADU? One size does not fit all –Except for Constant bitrate (CBR) Channels and CBR codecs Most 3G networks provide multiple PDU sizes to support “Bandwidth on Demand” Entropy in multimedia content (video, speech, Audio, …) is not constant over consecutive analysis windows –Variable bitrate (VBR) encoding: improved compression efficiency Examples –cdma2000 vocoders –Channel: RS-1 and RS-2 support 4 PDU sizes in addition to dtx –Source: cdma2000 vocoders generate 4 ADU sizes, based on source characteristics –SO60: ADU = PDU; CS like efficiency in PS! –ITU and MPEG Video codecs use VBR rate control –Constraints on rate control to generate ADUs of known sizes –Improved error resiliency when ADUs are matched to PDUs Significant statistical multiplexing gains when codecs are optimized to lower layers Challenges: Optimize 3G services, without cross-layer violations and maintain interoperability with other networks

TSG-C SWG1.2 Multimedia Services 9/21 Jitter in Packet Arrival

TSG-C SWG1.2 Multimedia Services 10/21 Jitter - PS Network Effects Variance in the ADU inter-arrival time –SDUs queued behind cross-traffic in routers –Routing changes in end-to-end path De-jitter buffer –a buffer to restore constant inter-packet timing prior to decoding –Increases playout delay 20ms De-jitter buffer Decoder Even delivery of voice frames 20ms of voice per frame per frame 20ms Variable Delay, in-order delivery not guaranteed

TSG-C SWG1.2 Multimedia Services 11/21 Jitter – Example packet arrival

TSG-C SWG1.2 Multimedia Services 12/21 Jitter – Example Packet Loss

TSG-C SWG1.2 Multimedia Services 13/21 “Smarter” Decoders They can reduce playout delay with variable rate rendering –Speech: Signal processing tricks such as “Time Warping” –Video: Audio visual synchronization (lip-synch) –Skewable video frame playback? They have Improved concealment techniques to mitigate packet loss –Interpolation in time and/or frequency domains Challenges –Develop improved objective metrics and subjective evaluation methodologies –Study and characterize the effects of such enhancements on user experience GoodErasureGood Playback Time line CircuitVoIP

TSG-C SWG1.2 Multimedia Services 14/21 Quality Evaluation Example: objective metrics for video

TSG-C SWG1.2 Multimedia Services 15/21 RTP Packet Loss Simulator SWG1.2 Simulation methodology to characterize multimedia content in cdma2000 wireless IP TBD: Packet loss rate due to jitter delay bound

TSG-C SWG1.2 Multimedia Services 16/21 Example: Video: Channel errors SCH 8x in RC3 (PDU size = 160 octets) Channel = Model A (Ped 3km/h) FER = 1%; Active set = 1; Geometry = 6dB Frame (10 fps) PSNR (clean)32.5 dB32.3 dB33.3 dB31.3 dB PSNR (errors)20.1 dB21.3 dB13.2 dB17.5 dB

TSG-C SWG1.2 Multimedia Services 17/21 What do we measure? Objective metric: PSNR averaged over the session –Usage is similar to that as MOS for vocoders –Not informative in error prone conditions New Objective Video Quality metrics in SWG1.2 –Percentage Degraded Video Duration (pDVD) –Standard deviation of PSNR (STD_PSNR) ovaer the session –In addition to average PSNR SWG1.2 objective metrics correlate well with subjective quality

TSG-C SWG1.2 Multimedia Services 18/21 Summary Optimize codecs and bearer protocols to lower layers for efficient IP services –e.g. VBR codecs and VBR channels in 3GPP2 CS voice –Rate control and RTP packetization to maximize “goodput” –Interoperability with other IP networks Develop smart codecs –Improved error resiliency –Better concealment techniques –Variable rate rendering Develop/adopt suitable objective metrics and subjective evaluation methodologies –Characterize user experience in realistic 3GPP2 environments

TSG-C SWG1.2 Multimedia Services 19/21 Backup Slides

TSG-C SWG1.2 Multimedia Services 20/21 1Q2Q3Q4Q 2006 TSG-C SWG 1.2 Multimedia Work-Plan H2H4Q Q2Q1Q 4Q3Q 2004 C.P0050-A File Formats C.P BCMCS Codecs Protocols Existing 3GPP2 work items Scenario only C.P MMD/PoC Codecs C.P PS Video Telephony C.P MMS Streaming C.P0050-B (Adv File Formats) C.P0046-A Adv Streaming) C.P0055-A Multiparty PS Video Telephony C.P00xx-0 (DSR) C.P MSS Char C.P BCMCS Char C.P100?-0 PSVT Char C.P0045-A MMS CodecsR&F–V&V Technical Reports Technical Specifications

TSG-C SWG1.2 Multimedia Services 21/21 SpecificationOutputStartExpected Publication Status Open Contr. Status Approved Contr. Comments MMS Codecs and Media Formats - C.P0045-A C.S0045-ADec 2005 MSS Multimedia Streaming - C.P C.S0046-0Dec 2001 MSS Advanced Multimedia Streaming - C.P0046-A C.S0046-AJul 2004 File Formats for Multimedia Services - C.P0050-A C.S0050-A PS Video Telephony -C.P C.S BCMCS Codecs and Transport Protocols - C.P C.S0070-0Jan 2005 MMD and PoC Codecs and Transport Protocols - C.P C.S0071-0Dec 2005 Multimedia Streaming Performance Characterization - C.P C.R1002-0Jul 2004 BCMCS Performance Characterization - C.P C.R1003-0Jan 2005 File Formats C.S0050-B PSVT Performance Characterization Multiparty PSVT - C.S0055-A DSR – C.S00xx TSG-C SWG 1.2 Multimedia Work-Plan