Home Gateway for Three-Screen TV Using H.264 SVC and Raptor FEC IEEE Transactions on Consumer Electronics, Vol. 57, No. 4, November 2011 Eun-Seok Ryu and Nikil Jayant

Outline Background Introduction Proposed Method Experimental Results Recent Research Conclusion

Background Home Gateway Three-screen Service The home gateway is an intelligent network interface device located at the consumer premises. It enables residential user to access the internet services delivered to home and also to access the different services offered by various smart devices located within home. Three-screen Service is a multimedia service and provides the right solution for consumers to access rich multimedia resources on any device, anytime, and anywhere.

Background Scalable Video Coding H.264/SVC is in particular of importance because it envisions methods for controlling video characteristics such as resolution, quality, and frame rate according to the network condition. For this purpose, SVC uses a layered coding approach to provide combined spatial, temporal, and quality scalabilities.

Background Scalable Video Coding SVC coding has several advantages : reduce total bandwidth, storage, and computational complexity by supporting many clients with a single video content file. applicable to many unequal error protection (UEP) methods using priorities of each layer. SVC approach is inherently more robust because of its error resilient tools. SVC 本身的 error resilient coding 會導致 bandwidth 浪費，尤其是 PLR 很小的時候，所以才選用 rateless code 做 protection

Background Raptor FEC The Raptor FEC was developed by Amin Shokrollahi as one of fountain codes in 2001 and is also called a rateless code. Several standards have adopted Raptor code as a standard: Multimedia broadcast and multicast services (MBMS) in the 3rd generation partnership project (3GPP) DVB-H Reliable multicast transport (RMT) working group within the internet engineering task force (IETF). The Raptor FEC can be designed with both the systematic and non-systematic approaches.

Background Raptor FEC Encode 因為 feedback information 在對多個 clients 時的負擔很大，所以用 rateless code 的特性 : 當 data 收足夠多時就可以解了

Outline Background Introduction Proposed Method Experimental Results Recent Research Conclusion

Introduction According to the annual Cisco visual networking index (VNI) forecast: 2009-2014, the sum of all forms of videos will continue to exceed 91 percent of global consumer traffic. TV VoD internet video peer-to-peer These show the importance of home multimedia technology in near future.

Introduction Video service providers (VSP) are preparing premium services. The home gateway and three-screen clients are as followed.

Introduction A traditional solution for source coding is to prepare separate pre-encoded video streams according to the capability of each targeted device. Another advanced solution is transcoding one high resolution and high bit rate video sequence for targeted screen sizes and bit rates of TV clients.

Introduction This paper proposes an elastic video streaming solution for 3STV and home gateway. SVC source coding technology to support various device capabilities with single bitstream. Raptor forward error correction technology to achieve strong packet loss recovery feature in application layer.

Introduction This paper proposes optimized video streaming methods with SVC and Raptor FEC. adaptive SVC layer-switching method, which enables the server to perform selecting appropriate according to bandwidth. adaptive Raptor FEC method, which controls the overhead of Raptor FEC according to PLR. The advantage of an efficient combination of (1) and (2) is that the optimal layer numbers to be sent under permitted bandwidth. the overhead of Raptor FEC to protect the packets of selected layers according to link quality.

Outline Background Introduction Proposed Method Experimental Results Recent Research Conclusion

Adaptive SVC Layer-switching with Raptor FEC Overhead Control Conceptual procedures of the proposed method Received Signal Strength Indicator (RSSI)-based feedback First, the server determines the layers to be sent when it initiates a session with the client. Second, it controls the Raptor overhead rate according to feedback of channel condition. Third, it decreases the number of layers to be sent as a layer-switching step and recalculates the Raptor overhead.

Adaptive SVC Layer-switching with Raptor FEC Overhead Control System architecture of implemented home gateway

Adaptive SVC Layer-switching with Raptor FEC Overhead Control is a reliable method for automatic switching between the several spatial/temporal layers. is the easiest natural bandwidth adaptation method in the middle of streaming. Besides, it has very low computational complexity because of the layered architecture of SVC. the VSP server sends whole layers of SVC video sequence to individual home, and the switching is performed in the gateway server as it responds to feedback of link quality from the client.

Adaptive SVC Layer-switching with Raptor FEC Overhead Control Adaptive Raptor FEC Raptor FEC shows excellent packet loss recovery results in various PLR conditions, for any given overall FEC overhead rate. The proposed method determines the Raptor overhead according to feedback of channel condition based on these experimental results as an overhead adaptation method.

Adaptive SVC Layer-switching with Raptor FEC Overhead Control The flow chart of algorithm for SVC layer and Raptor overhead adaptation

Outline Background Introduction Proposed Method Experimental Results Recent Research Conclusion

Experimental Results Implementation The implemented environment for the 3STV home gateway includes: two laptops with one large size TV, and one personal digital assistant (PDA). 802.11b wireless LAN is used for the in-home wireless network. TCP is used for sending control messages such as the feedback of channel condition. Real-time Transport Protocol over UDP is used for streaming video sequence.

Experimental Results Sample video sequences for three-screen TV

Experimental Results Overall bit rate gains Overall bit rate gains : about 28% - 36% over AVC at three quality levels (Ski sequence).

Experimental Results Performance of adaptive Raptor FEC and SVC layer-switching

Experimental Results Comparison of video quality by streaming methods (from left 3%, 5%, 10%, and 15% PLR condition).

Experimental Results Moving traces with mobile TV on building map

Experimental Results Reactions of the proposed method in real moving experimentation using implemented home gateway system

Outline Background Introduction Proposed Method Experimental Results Recent Research Conclusion

Multilevel Diversity Coding via Rateless Codes for Reliable and Scalable Video Multicasting IEEE Communications Letters, Vol. 17, No. 5, May 2013 Mohsen Sardari, Eun-Seok Ryu, Faramarz Fekri, and Nikil Jayant

Multi-gateway Structure Clients in different coverage regions can connect to a number of gateways (top). Association of each client to more gateways result in higher quality (bottom).

Multi-gateway Optimization Benefit : reducing the load on the backbone network. This paper formulates the problem as an optimization problem with the objective of minimizing the total bandwidth of the scalable video delivery.

Multi-gateway Optimization This paper first introduces an abstract model and describe the optimal solution for multi-gateway multicast of scalable content. And demonstrates that traditional multicast, which requires all the gateways in the network fully deliver all the layers of a SVC content, is not optimal.

Multi-gateway Optimization Consider a source node S which provides scalable video with L layers l1, . . . , lL . This paper optimize for the total output rate of the S such that connection to any Nα number of gateways should enable the client to successfully receive layers {l1, . . . , lα}.

Multi-gateway Optimization Consider the n-th gateway and let r1n , r2n , . . . , rLn be the rate of the layers 1 through L provided by S to the n-th gateway. The total rate sent to n-th gateway :

Multi-gateway Optimization To successfully recover a layer α, the sum of the rates rα ≥ 0 received by a client from all the gateways should be lα. Therefore, constraints on successful recovery of layers result in the following optimization problem :

Multi-gateway Optimization Thus, the dual problem of optimization with variables p1, . . . , pL, is

Multi-gateway Optimization The solution of the optimization problem :

Multi-gateway Optimization In [10], it is shown that given enough budget for storing a file in a distributed network, spreading of the budget maximizes the recovery probability for a collector with random access to a set of storage nodes. [10] D. Leong, A. Dimakis, and T. Ho, “Distributed storage allocations,” IEEE Trans. Inf. Theory, vol. 58, no. 7, pp. 4733–4752, July 2012.

Achieving the Optimal Solution with Rateless Coding Source S should provide every gateway the whole of layer 1, and 1/i of the layer i. The property of rateless coding provides the flexibility to encode data on the fly and proves to be useful in achieving the optimal solution.

Comparison of the Optimal Solution with Simple Multicast Gain of various layer growths

Experimental Results Performance evaluation Overhead r = 12%

Conclusion Adaptive SVC layer-switching selects appropriate layers to be sent according to ABW by RSSI-based feedback. Raptor FEC overhead control method controls its overhead according to PLR. The proposed method outperforms traditional methods and enhances video quality from 2dB to 5dB while simultaneously reducing bitrates from 28% to 36% .