A low-latency yet highly reliable wireless video transfer system

Transcription

1 A low-latency yet highly reliable wireless video transfer system Tobias Welti Institute of Embedded Systems Team High Performance Multimedia & Data Acquisition

2 Target Specifications 30 fps interactive large data low-latency volume highly reliable wireless video transfer use tablet computer IEEE no dropped frames 2

3 Interactive Applications Photo: Hubsan 3

4 Live Interview on TV 4 SRF

5 Remote Controlled Drone (FPV) Photo: Hubsan Photo: Skyzone 30 km/h: 2.1 m in 250 ms Wireless Technology Band Latency IEEE / 5 GHz 250 ms Wideband FM 5.8 GHz ms Wireless HD 60 GHz 30 ms 5

6 System Description Camera Unit IEEE ms Display Unit Photo: Hubsan Photo: Apple Inc. 6

7 Sources of Latency Processing Transmission Processing ms 7

8 Low Latency: How-To Problem Processing Time Idea Get a head start Transmission Speed Transmission Amount Retransmission 8

9 Get A Head Start Image Sensor Image Processor Image Buffer (400 lines, 33 ms) Image Sensor Image Buffer (16 lines, 1.3 ms) Image Processor 9

10 Pipelining A B C time step 1 A B C step 2 A B C A B C step 3 A B C A B C step 4 A B C transmission A B C 10

11 Low Latency: How-To Problem Processing Time Transmission Speed Idea Get a head start Transmit fast Solution Pipelining, small buffer Transmission Amount Retransmission 11

12 IEEE g vs IEEE n 12

13 Transmission Latency Single uncompressed TV frame: 3.3 Mbit Mbps ms fps Markus Bertschi

14 Congestion 14 defensivedriversdiscount.com Barry Belfast Batchelor, Telegraph PA

15 Available Channels 5 GHz 23 Channels (CH) No Overlap Moderate use 15

16 Available Channels 2.4 GHz 14 Channels Overlap Heavily used 16

17 Congestion Setup Ch 1, max speed Measuring AP Measuring STA Ch 1/2/3, 100 kbps..100mbps Jamming AP Jamming STA 17

18 Congestion 18

19 Low Latency: How-To Problem Processing Time Transmission Speed Transmission Amount Idea Get a head start Transmit fast Send less data Solution Pipelining, small buffer Use multiple streams Retransmission 19

20 Kompression JPEG/MPEG H.264 H.265 Lossless: factor 2..3 Lossy: factor

21 Low Latency: How-To Problem Processing Time Transmission Speed Transmission Amount Idea Get a head start Transmit fast Send less data Solution Pipelining, small buffer Use multiple streams Compress data Retransmission 21

22 The Problem: Packet loss 22

23 Retransmission Standard Multicast 23

24 Low Latency: How-To Problem Processing Time Transmission Speed Transmission Amount Retransmission Idea Get a head start Transmit fast Send less data Alternative Reliability Scheme Solution Pipelining, small buffer Use multiple streams Compress data 24

25 Forward Error Correction 25

26 Low Latency: How-To Problem Processing Time Transmission Speed Transmission Amount Transmission Reliability Idea Get a head start Transmit fast Send less data Avoid Retransmission Solution Pipelining, small buffer Use multiple streams Compress data FEC, Backup Stream 26

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31 Low Latency: How-To Problem Processing Time Transmission Speed Transmission Amount Transmission Reliability Idea Get a head start Transmit fast Send less data Avoid Retransmission Solution Pipelining, small buffer Use multiple streams Compress data FEC, Backup Stream 31

32 Our Solution Processing Transmission Processing ms 100 ms 32

33 Conclusion Don t buffer whole image Pipelined processing Use suitable wireless standard Apply adaptive compression Additional reliability methods 33

34 Applications? Photo: Hubsan 34