Wenjun Hu
ABSTRACT
A key challenge for smartphone based visual communication over screen-camera links is imperfect frame synchronization. The difficulty arises from frame rate diversity and variability due to camera capability, lighting conditions, and system factors. On the 4 smartphone cameras we tested, the frame rate varies between 8 and 30 frames per second. If the transmit frame rate is too high, the receiver might lose original frames or capture mixed frames, which are normally not decodable. Previous systems simply reduce the effective screen frame rate to be half the camera frame capture rate, to guarantee receiving a decodable frame every other frame. This under-utilizes the transmitter side capacity and is inefficient.
We achieve frame synchronization with LightSync, which features in-frame color tracking to decode imperfect frames and a linear erasure code across frames to recover lost frames. LightSync allows smooth communication between the screen and the camera at any combination of the transmit and receive frame rates, as long as the receive rate is at least half the transmit rate. This means that each receiver can scale the decoding performance with its own camera capability. Across several phones, our system can more than double the average throughput compared to previous approaches.
- Gibraltar targets tourists with Wikipedia QR codes. http://www.bbc.co.uk/news/technology-19544299.Google Scholar
- HTC One X specification. http://www.gsmarena.com/htc_one_x-4320.php.Google Scholar
- Huawei Ascend C8812E specification. http://pdadb.net/index.php?m=specs&id=3532&c=huawei_ascend_c8812.Google Scholar
- Mary Meeker's 2013 Internet Trends Report. http://allthingsd.com/20130529/mary-meekers-internet-trends-report-is-back-at-d11-slides/.Google Scholar
- Nokia Lumia 920 specification. http://www.gsmarena.com/nokia_lumia_920--4967.php.Google Scholar
- QR codes improve shopping experience. http://www.iogear.com/blog/2011/03/15/qr-codes-improve-shopping-experience/.Google Scholar
- Samsung Galaxy S III specification. http://www.phonearena.com/phones/Samsung-Galaxy-S-III_id6330.Google Scholar
- A. Ashok, M. Gruteser, N. Mandayam, J. Silva, M. Varga, and K. Dana. Challenge: Mobile optical networks through visual MIMO. In Proceedings of MobiCom, 2010. Google ScholarDigital Library
- T. Hao, R. Zhou, and G. Xing. COBRA: Color Barcode Streaming for Smartphone Systems. In Proceedings of MobiSys, 2012. Google ScholarDigital Library
- S. Hranilovic and F. R. Kschischang. A Pixelated MIMO Wireless Optical Communication System. IEEE Journal of Selected Topics in Quantum Electronics, 2006.Google Scholar
- K. Jamieson and H. Balakrishnan. PPR: Partial packet recovery for wireless networks. In ACM SIGCOMM, 2007. Google ScholarDigital Library
- T. Langlotz and O. Bimber. Unsynchronized 4D Barcodes Coding and Decoding Time-Multiplexed 2D Colorcodes. In Proceedings of the International Symposium on Visual Computing, 2007. Google ScholarDigital Library
- M. Nakagawa. The world of visible optical communication - It opens with LED -- Light Communications. Kogyo Chosakai Publishing, Inc.Google Scholar
- G. Pang, T. Kwan, H. Liu, and C. Chan. LED Wireless. IEEE Industry Applications Magazine, 2002.Google Scholar
- S. D. Perli, N. Ahmed, and D. Katabi. PixNet: LCD-camera pairs as communication links. In Proceedings of MobiCom, 2010.Google ScholarDigital Library
- M. Rohs. Real-world Interaction with Camera-Phones. In Proceedings of the International Symposium on Ubiquitous Computing Systems, 2004. Google ScholarDigital Library
- P. Vartiainen, S. Chande, and K. Ramö. Mobile Visual Interaction: Enhancing Local communication and Collaboration with Visual Interaction. In Proceedings of the International Conference on Mobile and Ubiquitous Multimedia, 2006. Google ScholarDigital Library
- G. Woo, A. Lippman, and R. Raskar. VRCodes: Unobtrusive and Active Visual Codes for Interaction by Exploiting Rolling Shutter. In IEEE International Symposium on Mixed and Augmented Reality, 2012. Google ScholarDigital Library
Index Terms
- LightSync: unsynchronized visual communication over screen-camera links
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