APPLICATION-LAYER ERROR RESILIENCE FOR WIRELESS IP-BASED Video Broadcasting

1. SHEAU-RU TONG Management Information System Dept., National Pingtung University of Science and Technology, Taiwan (R.O.C.) srtong@mail.npust.edu.tw YUAN-TSE YU Dept. of Software Engineering National Kaohsiung Normal University, Taiwan (R.O.C.) yuyt@nknucc.nknu.edu.tw APPLICATION-LAYER ERROR RESILIENCE FOR WIRELESS IP-BASED Video Broadcasting

2. Background Replicate Multiple Descriptor (RMD) Coding Simulation and Performance Evaluation Conclusions Outline

3. Multi-path fading and fast interference in wireless networks causes heavy packet loss burst and poor video broadcast quality. Low-layer forward error coding (FEC) is suitable for fixing short-term loss burst, but not for long-term loss burst. Background

4. A HSDPA traffic trace (with link-layer FEC) of a moving vehicle where multiple-packet-loss events frequently occur. Background

5. Multiple descriptor coding (MDC): • Split a video stream into several sub-streams (descriptors) • Encode each sub-stream independently and transmit them over different data paths. • Exploiting path diversity. • Protecting key-frame is more efficient! Background Application-layer error resilience is desirable!

6. Basic idea: logically applying MDC in the application layer with two new features. • Replicate key-frames • Interleave multiple descriptors over an IP multicast channel. • Advantages: • Distributing long loss burst over multiple descriptors to mitigate the damage impact. • Exploiting time diversity of key frame transmission. Replicate Multiple Descriptor (RMD)

7. The system architecture of RMD Replicate Multiple Descriptor (RMD)

8. Frame replication/insertion • b: the number of replicas. • s: the number of the frame slots shifted. Replicate Multiple Descriptor (RMD)

9. Analysis of RMD • Frame slot time (Isub-stream) where k is number of sub-streams, r video data rate and p GOP size. • Delay (D) and buffer space (B) where SI and SO are the maximum frame size of I frames and the other frames, respectively. Replicate Multiple Descriptor (RMD)

10. Key frame error probability (Pkf_err) where e is the packet slot error rate, g is the number of packets for an I frame. Replicate Multiple Descriptor (RMD) P­kf_err with respect to various b’s when k=4 and g=4.

11. Simulation configurations • 400 frames MPEG-4 with a QCIF format. • 30 fps with GOP pattern of IPPPPPP. • Packet size of 1024 bytes • Comparing RMD with • Single Descriptor (SD) • Multiple Descriptors (MD) • SD/FEC(255, 159) • MD/FEC(255, 159) Simulation and Performance Evaluation

12. Simulation and Performance Evaluation • When the packet loss rate increases beyond 15%, RMD starts to outperform SD/FEC or MD/FEC (PSNR>21dB).

13. Simulation and Performance Evaluation • The instances of PSNR with respect to various schemes when packet loss rate e = 20%. RMD protects the key frame better!

14. Simulation and Performance Evaluation • Impact of b and s in RMD • The PSNR curve is improved (leveraged) as s and b increases. • The improvement is magnified under a heavy packet loss condition (15%-35%) Average PSNR of RMD with respect to various s’es when b=2. Average PSNR of RMD with respect to various s’es when b=3.

15. Redundancy cost (ε =20%) • RMD (b=3) has a redundancy ratio slightly higher than that of MD/FEC, but can gain a PSNR about 5 dB. Simulation and Performance Evaluation

16. RMD is an ideal application layer approach for combating excessive burst errorsand protecting key frames. RMD (b=3) has a redundancy ratio slightly higher than that of MD/FEC, but can gain a PSNR about 5 dB subject to ε =20%. How to co-work RMD with other adaptive FEC to offer a full spectrum of protection against various burst errors is worthy of further study. Conclusions