IPTV 서비스 품질 기술

이 철 희

연세대학교

채널 용량이 증대함에 따라 네트워크를 이용하여 새

로운 서비스 가능

멀티미디어 서비스 (VOD, MOD, 화상전화 등)

IPTV

인터넷, 무선 통신 등이 주요 역할 기대.

네트워크를 이용한 멀티미디어 서비스

HDSP lab. 2

기존 방송

대역폭 보장됨

적절히 설치되면 일반적으로 품질 보장

전송에러 거의 없음

실시간 전송이 아무 문제 없음

네트워크를 이용한 멀티미디어 서비스 (IPTV 등)

대역폭 보장 어려움

데이터 폭주 시 품질 저하

실시간 전송을 보장하기 어려움

네트워크를 이용한 멀티미디어 vs 기존 방송 비교

HDSP lab. 3

기존 방송

시청료

광고수입

네트워크를 이용한 멀티미디어 서비스 (IPTV 등)

시청료

광고수입

PPV (VOD, contents-based billing)

품질 보장 필요.

수익구조

HDSP lab. 4

통신망을 이용함으로 기존에 불가능했던 새로운 서

비스 가능.

개인 수요 맞춤형 서비스

무제한 프로그램 제공 가능

국경에 영향 받지 않음

이동 중에도 이용 가능

네트워크를 이용한 멀티미디어 서비스 장점

HDSP lab. 5

100% 품질 보장 불가능.

PPV에서는 품질 보장 필요.

열화 발생 시, 쌍방이 동의 할 수 있는 방법으로 요금

정산 필요

품질 모니터링은 중요한 문제로 부각.

품질 측정에 관한 국제 표준 필요.

Challenges of Multimedia Services over Networks

HDSP lab. 6

QoE Requirements for IPTV

QoE for video

Resolution , bit rate, application layer video encoding,

encoder setting (GOP)

Codec: MPEG-2, MPEG-4 AVC (MPEG-4 Part 10 or H.264),

SMPTE VC-1

Video Requirements for IPTV: video

HDSP lab. 8

2.1 Mbps CBR / 10 MbpsSMPTE VC-12.1 Mbps CBR / 10 MbpsMPEG-4 AVC (Main profile at Level 3)

3.18 Mbps CBR / 15 MbpsMPEG-2 - Main profile at Main level (MP@ML)

Minimum Bit Rate (SD / HD)Video Codec

QoE for audio

channels: mono, stereo, 5.1 channels

sampling rates: 16-48kHz

Audio Requirements for IPTV

HDSP lab. 9

128StereoMP3 (MPEG-1, Layer 3)

96 for stereoStereoAAC

384 for 5.1 / 128 for stereo5.1 if available, elseleft/right stereo pair

Dolby Digital (AC-3)

128 for stereoMono or stereoMPEG Layer II

Minimum Bit Rate (kbps)채널수오디오 코덱

45 ms maximum15 ms maximum

Audio Lag VideoAudio Lead VideoAudio – Video Synchronization

QoE for control functions

채널 변경시간

VOD trick mode

QoE for EPG

사용자 편의성

응답시간

QoE for Metadata: Availability, Data size, Correctness

QoE for Browser: Characteristics of a television set, TV-like display, 글자

크기, Navigation, Cookie

QoE Requirements for IPTV

HDSP lab. 10

Traffic management

Application layer reliability solutions

품질 보증을 위해 취할 수 있는 방법

HDSP lab. 11

Control plane

Data plane

Multicasting

Traffic Management for IPTV

HDSP lab. 12

Control Plane

admission control (IETF RFC 2753)Admission control meets requirements for IPTV multicast/unicast services as negotiated in the

SLA.

The network needs to properly engineered to accommodate the number of subscribers.

QoS routing (ITU-T Rec Y.129)This method is used to control network congestion and improve network utilization by selecting

an appropriate path

Resource managementnetwork traffic management according to the network information by means of data

transmission between the network resource manager and the network nodes

Traffic Management for IPTV

HDSP lab. 13

Data Plane

Traffic conditioning (required in access

network)

• QoS provisioning per subscriber and per service

• Traffic classification based on multiple header fields (5-tuple, 6-tuple, and etc.)

• Minimum bandwidth guarantee

• Traffic shaping/policing

• Advanced packet queuing and scheduling

• Traffic marking (DSCP, 802.1p, and etc.)

Traffic Management for IPTV

HDSP lab. 14

Data Plane

Transmission schedulers

First-in, first-out scheduler

Round-Robin Scheduler

Priority scheduler

Weighted Round-Robin scheduler

Class-based schedule

Buffer management

Traffic Management for IPTV

HDSP lab. 15

Multicasting

Multicast replication point

Traffic Management for IPTV

HDSP lab. 16

Traffic Management for IPTV: Y.1541 – IP network QoS class definitions and network performance objectives/Applications

HDSP lab. 17

Network QoS Classes

ITU-T Recommendation Y.1541 (8 QoS classes) 등을 참고하여 IPTV

규격 논의 중

IPTV 서비스를 5가지 경우로 분류

① Best Effort 서비스 (QoS class 5): content download 서비스, 정기적인 정보

제공, T-information, 이메일

② Low Loss 서비스 (QoS class 4): VOD, MOD, T-commerce, VOD 기반 T-

learning

③ Interactive 서비스 (QoS class 2/3): 메신저, T-learning based on interactive

④ Real-Time Interactive 서비스 (QoS class 0/1): VOIP, 화상전화, 다자간 게임

⑤ Real-Time Multicase & Unicast 서비스 (QoS class 6/7): linear/broadcasting,

multi angle, PPV, PVR

Traffic Management for IPTV

HDSP lab. 18

Cross-layer interaction for IPTV services

Traffic management capabilities: core networks

Traffic management capabilities: acces networks

Traffic management capabilities: home networks

Traffic Management for IPTV

HDSP lab. 19

Application Layer Reliability Solution for IPTV

전송 오류 복구 방법

Retransmission

FEC (Forward Error Correction)

hybrid combinations of both

Application Layer Reliability Solution for IPTV

HDSP lab. 21

Retransmission

HDSP lab. 22

draft-ietf-avt-rtcpssm-13.txt[IETF AVT-RTCPSSM]

Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF)

[IETF RFC4585]

Real Time Protocol Control Protocol Extended Reports (RTCP XR)

[IETF RFC3611]

Real Time Control Protocol (RTCP) Attribute in Session Description Protocol (SDP)

[IETF RFC3605]

Session Description Protocol (SDP) Bandwidth Modifiers for RTP Control Protocol

[IETF RFC3556]

Real Time Protocol: A Transport Protocol for Real-Time Applications

[IETF RFC3550]TitleReference

Forward Error Correction (FEC) at the Application/Transport layers

Packet erasure correction techniques

FEC for Streaming Applications

IETF RFC2733 [IETF RFC2733]

3GPP TS26.346 Multimedia Broadcast/Multicast: Protocols and

Codecs [3GPP TS26.346]

ETSI EN301 192 Digital Video Broadcasting: DVB Specification for

Data Broadcasting [ETSI EN301 192]

ETSI TS 102 034 1.3.1 Transport of MPEG 2 Transport Stream

(TS) Based DVB Services over IP Based Networks [ETSI TS

102 034]

FEC (Forward Error Correction)

HDSP lab. 23

IETF RMT working group standardizes protocols for

reliable file delivery over IP multicast.

FEC for Download Services

HDSP lab. 24

FLUTE - File Delivery over Unidirectional Transport[IETF RFC3926]

Compact Forward Error Correction (FEC) Schemes[IETF RFC3695]

The Use of Forward Error Correction in Reliable Multicast[IETF RFC3453]

Forward Error Correction Building Block[IETF RFC3452]

Layered Coding Transport (LCT) Building Block[IETF RFC3451]

Asynchronous Layered Coding Protocol Instantiation[IETF RFC3450]

Author Guidelines for RMT Building Blocks and Protocol Instantiation Documents

[IETF RFC3269]

Reliable Multicast Transport Building Blocks for One-to-Many Bulk-Data Transfer

[IETF RFC3048]

The Reliable Multicast Design Space for Bulk Data Transfer[IETF RFC2887]

TitleReference

Performance Monitoring for IPTV

현재 인터넷은 특성상 bandwidth 보장 어려움

품질은 전송상태에 따라 가변적임

필연적으로 발생하는 품질저하문제를 서비스 제공업

자 및 사용자가 동의할 수 있는 방법으로 해결 필요.

특히 화상전화, pay-per-view에서는 품질에 근거한

과금 필요

이를 위하여 체감 품질 모니터링 기술 필요

Performance Monitoring for IPTV

HDSP lab. 26

모니터링 파라미터

– Physical Layer Parameters

– IP Layer/Network Parameters

– Transport Stream parameters

– Service Line-Up parameters

– Channel Attribute parameters

– VOD Parameters

– Other Parameters

Performance Monitoring for IPTV

HDSP lab. 27

Physical Layer Parameters

① RF intergrity

② Available bandwidth

Performance Monitoring for IPTV

HDSP lab. 28

IP Layer/네트워크 파라미터

① Link IP layer used/available bandwidth

② End-to-end IP layer bandwidth

③ End-to-end IP layer available bandwidth

④ Loss run length distribution

⑤ Error-free interval distribution

⑥ Packet loss metrics and models

⑦ Streaming jitter

Performance Monitoring for IPTV

HDSP lab. 29

Service Line-Up parameters

Video

Audio

Meta data

• Subtitles

• EPG

• Parental control

Performance Monitoring for IPTV

HDSP lab. 30

Service Line-Up parameters

Channel line up

Service meta-data (eg. EPG, subtitles, parental control, etc.)

Channel zap time

Correctness Rate

Channel Attribute parameters

Channel attributes

Video quality

Audio quality

Ancillary channel associated attributes (subtitles, closed captions, descriptive audio)

VOD Parameters

Performance Monitoring for IPTV

HDSP lab. 31

Monitoring Methods

Generalized monitoring method for multi-media data

based on transmission packet loss

Bearer network monitoring

Network performance monitoring

IPTV service attribute monitoring

Video quality monitoring

Audio quality monitoring

Performance Monitoring for IPTV

HDSP lab. 32

• Full Reference (전기준법)– 기준영상 제공

– 응용분야: Codec 성능 평가, 디지털 방송, 멀티미디어 장비 성능평가

• Reduced Reference (감소기준법)– 압축영상과 reference bit-stream 함께 전송

– 허용 reference bit-stream: 10Kb, 56Kb, 256Kb– 응용분야: 무선 통신 멀티미디어 전송, 채널 상태에 대응하여

parameter 최적화

• No Reference (무기준법)– 수신 동영상만으로 화질평가

– 상대적으로 신뢰도 저하

– 응용분야: 무선 통신 멀티미디어 전송, 채널 상태에 대응하여parameter 최적화

객관적 화질 평가 방법 분류

HDSP lab. 33

객관적 화질 평가 시스템 구성도

HDSP lab. 34

Encoder Decoder

Digital Channel

Video Source

FRFR

RRRR RRRR

NRNR

Performance Measurement system

Extracted Feature

Multimediaterminal

전송에러를 이용한 화질평가 방법 (J.242)

• 패킷을 사용한 비디오 전송에서는 전송에러정보를 이용하여 수신 동영상 추정가능

• 대역폭 사용을 최소화하면서 수신측의 화질 모니터링 가능

• IPTV , 화상전화, VOD 등에 적용 가능

encoder transmitter decoder

transmission errordetection unitreceived video

estimation unit

video qualityevaluation unit

sourcevideo

Head-end (service provider)Receiver

packetized video data

estimated received video

receivedvideo

Hybrid Perceptual/Bit-stream Models

decoderchannelPVS

Hybridperceptualbit-stream

NRmodel

bit-steamanalyzer

- codec parameters- bit rate- FPS- packet information if available- IP information- transmission error information(lost or delay packets, impaired blocklost or delayed frames)

Hybrid Perceptual/Bit-stream Models

objective modelcompression

error

encoderSRC

MUX

decoderchannelPVS

Hybridperceptualbit-stream

NRmodel

bit-steamanalyzer

- codec parameters- bit rate- FPS- packet information if available- IP information- transmission error information(lost or delay packets, impaired blocklost or delayed frames)

videoquality scores

Streaming Server with Quality Monitoring and Optimization

encoderSRCstreamingserver receiver

qualitymonitoring

channel

• Development of streaming server with quality monitoring capability and optimization.

• Optimization of streaming technologies based on quality monitoring results (e.g., codec parameter, application layer reliability solutions).