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

APPLICATION-LAYER ERROR RESILIENCE FOR WIRELESS IP-BASED Video BroadcastingSHEAU-RU TONGManagement Information System Dept.,National Pingtung University of Science and Technology, Taiwan (R.O.C.)srtong@mail.npust.edu.tw

YUAN-TSE YUDept. of Software Engineering National Kaohsiung Normal University, Taiwan (R.O.C.)yuyt@nknucc.nknu.edu.tw 1

1OutlineBackgroundReplicate Multiple Descriptor (RMD) CodingSimulation and Performance EvaluationConclusions2

2BackgroundMulti-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. 3

3BackgroundA HSDPA traffic trace (with link-layer FEC) of a moving vehicle where multiple-packet-loss events frequently occur.

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4BackgroundMultiple 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!

5Application-layer error resilience is desirable!

video stream is split into several sub-streams (descriptors), each of which is encoded and transmitted over different paths independently5Replicate Multiple Descriptor (RMD) Basic idea: logically applying MDC in the application layer with two new features.Replicate key-framesInterleave 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.6

6Replicate Multiple Descriptor (RMD) The system architecture of RMD7

7Replicate Multiple Descriptor (RMD)Frame replication/insertionb: the number of replicas.s: the number of the frame slots shifted.

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GOP(p, q), where p is the number of frames in a GOP and q is the number of frames between two neighboring I or P frames.8Replicate Multiple Descriptor (RMD) Analysis of RMDFrame 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.9

9Replicate Multiple Descriptor (RMD)Key frame error probability (Pkf_err)

where e is the packet slot error rate, g is the number of packets for an I frame.10

Pkf_err with respect to various bs when k=4 and g=4.

10Simulation and Performance EvaluationSimulation configurations400 frames MPEG-4 with a QCIF format.30 fps with GOP pattern of IPPPPPP.Packet size of 1024 bytesComparing RMD withSingle Descriptor (SD)Multiple Descriptors (MD)SD/FEC(255, 159)MD/FEC(255, 159)11

11Simulation and Performance Evaluation

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

MD shows a better PSNR compared with SD as the packet loss rate (i.e., e) increases.12Simulation and Performance Evaluation

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

13Simulation and Performance Evaluation

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

14Simulation and Performance EvaluationRedundancy cost ( =20%)RMD (b=3) has a redundancy ratio slightly higher than that of MD/FEC, but can gain a PSNR about 5 dB.15

15ConclusionsRMD is an ideal application layer approach for combating excessive burst errors and 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 =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.16

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