ON DATACASTING OF H.264/AVC OVER DVB-H Multimedia Signal Processing, 2005 IEEE 7th Workshop on Publication Date: Oct Nov Reporter: 陳志明 1

OUTLINE Introduction H.264/ AVC IP Datacasting in DVB DVB-H Enhancements to DVB-T MPE-FEC Evaluation of MPE-FEC Conclusions 2

INTRODUCTION Point-to-multipoint (PTM) broadcast/multicast type mobile communications is enabled through two well-known approaches. GPRS and UMTS systems DVB-T and DVB-H DVB-H uses the same basic concepts of DVB-T (such as MPE)but adds features such as time-slicing and Reed-Solomon (RS) forward error correction (FEC) codes for error resiliency. This paper focuses on MPE-FEC concept in DVB-H. H.264/AVC has been selected as the video codec for IP datacasting services over DVB channels, because it has been shown to provide superior compression efficiency compared to earlier standards. 3

H.264/ AVC H.264/AVC is designed as a two-layer abstraction Video Coding Layer Network Abstraction Layer The concept of slicing was developed to enable encoders to fit video data into the Maximum Transfer Unit (MTU) of a transmission channel. 4

IP DATACASTING IN DVB In order to provide additional services beyond traditional DTV, DVB has specified protocols allowing broadcast of program and non-program specific contents to be transmitted along with traditional DTV contents. This broadcast of data is called Datacasting. The popularity of the Internet and an urgent need for faster broadcast data rates led to the convergence of Internet and broadcast networks. Incompatibilities in IP and broadcasting protocol were handled by an intermediate encapsulation process called Multi-Protocol Encapsulation (MPE). 5

DVB-H ENHANCEMENTS TO DVB-T Handheld mobile terminals require specific features from the transmission system serving them. These features include : Extended receiver battery life Improved RF performance for mobile single antenna reception Counter high levels of noise in a hostile transmission environment Efficient handover An optional MPE-FEC protection 6

MPE-FEC MPE-FEC is an optional FEC code based on RS codes, and included in the DVB-H specifications to counter high levels of transmission errors. RS(255,191,64) ………….. 7

MPE-FEC The procedure to compute the RSDT 8

EVALUATION OF MPE-FEC MPE-FEC was included in DVB-H to improve unfavorable carrier-to-noise (C/N) condition that can occur in a typical terrestrial channel. This paper presents two evaluations : Increase in on-air bitrate (radio channel transmission bitrate) due to MPE-FEC and header overhead. Performance improvement due to MPE-FEC. 9

EVALUATION OF MPE-FEC Simulations are performed to evaluate the bitrate overheads and the correction capability of MPE-FEC. QCIF format video at 15 frames per second using an H.264/AVC Baseline Profile encoder. MPEG-2 TS error patterns with an error probability of 0.06, 0.07, and The number of MPE-FEC rows was set to 1024 and four different code rates (CR) of 1, 1/2, 3/4, 7/8 for the entire bitstream was simulated. 10

EVALUATION OF MPE-FEC The number of columns used for ADT, padding, RSDT and puncturing for the different CRs simulated. CR = ADT / (ADT + RSDT) 11

EVALUATION OF MPE-FEC Evaluation of MPE-FEC bitrate overhead Plots for IP bitrate, MPE along with MPE-FEC bitrate, and TS bitrate for CR 3/4 and row size

EVALUATION OF MPE-FEC Evaluation of MPE-FEC error protection capability error probability 0.06 error probability 0.07 error probability

CONCLUSIONS It showed how the choice of the IP packet size and the encoding bitrate can affect the on-air bitrate over a DVB- H channel. The simulation results suggest that MPE-FEC is essential for efficient H.264/AVC video reception. It also showed that the reception performance can be improved by identifying an optimal code rate. 14