Portable Device-Centric Streaming Service

Transcription

1 Portable Device-Centric Streaming Service Jin-Hwan Jeong 1, Hag-Young Kim 1, and Eunah Kim 2 1 Electronics and Telecommunications Research Institute, Gajeong-dong, Youseong-gu, Daejeon, Korea {jhjeong,h0kim}@etri.re.kr 2 Samsung Advanced Institute of Technology, Suwon, Korea eunah1004.kim@samsung.com Abstract. We envision a portable device-centric streaming service system. To cope with the demand for displaying contents stored in a portable device onto a high resolution display device, our system provides an autonomous and seamless device-centric streaming service model. As this model takes pairing phase via Bluetooth and streaming phase via broad band network, consumers do not need to know about specific information of nearby systems for streaming. Along with the user convenience, this approach saves battery power by yielding decoding and frame scaling to the better external device. This promises great convenience for users of HD video recordable consumer electronics. Keywords: Portable device, Device-centric, Pairing, Streaming. 1 Introduction With the advent of high performance HD video recordable portable devices, it is common to record high quality video at any time and video-oriented services come very popular. For example, when people find an interesting scene, they capture it using a portable recording device like cellular phones with easy. After authoring contents, they usually upload the contents to some websites or share them with others via s. Sometimes, they show captured contents to others directly. In case of playing contents on a portable device, due to the portability, the display of portable devices is so small in size that it is difficult to enjoy video occasionally. To play in high quality as originally encoded, a consumer may download the contents to high performance PC equipped with a larger LCD monitor. These processes are very common, but inconvenient, because customers need to know how to manipulate the devices and what device is proper to play contents. For the customer convenience, many device manufacturers have provided external memory slots or autonomous tools to transfer user contents to websites or other devices. In case of cellular phones, service carriers provide various applications specialized in their models for sharing contents with other devices. This approach apparently gives more convenience, but usually, it is applicable only to the same models. As illustrated in Fig. 1, SCH-W420 [1] model can capture high quality video with 2 Mega pixel-cmos Cam, and can communicate with a base station via HSPA (High Speed Packet Access) or can communicate with nearby Bluetooth devices. Also, this A. Mauthe et al. (Eds.): FMN 2009, LNCS 5630, pp , Springer-Verlag Berlin Heidelberg 2009

2 Portable Device-Centric Streaming Service X 482 Touch Screen LCD Bluetooth, HSDPA 7.2Mbps 2.0 Mega-Pixel Camera MicroSD external memory slot Fig. 1. Summary of SCH-W420 hardware specification model has a high performance processor and media coprocessor, so it is capable to capture video and send/receive data. However, due to the portability, it has a relatively small LCD in resolution (about a quarter of HD size) compared with the capability of its equipped camera. In other words, the resolution of LCD is not enough to display the captured video. If a consumer wants to play the captured video in a large display, video files should be transferred via HSUPA (High Speed Uplink Packet Access) or Bluetooth, or files should be stored in an external memory card to be carried. In this case, a consumer may encounter some problems. In real, the problems are arising not from the absence of tools nor applications, but come from locating and enumerating the peer system. At first, users should know about target devices, which means that if a user wants to transfer to a certain device, he/she should know explicitly the address such as device ID or IP address of it. Another limitation is that a user may know the way of communication method and may be forced to select the communication interface. These limitations are a big hurdle for common users not familiar with digital devices. In this paper, to eliminate the mentioned limitations, we propose a portable devicecentric streaming service system. This service system is roughly divided into two phases, device pairing phase and streaming phase. With the first phase, a user needs not to know about specific information of the peer device. After device pairing, our system does streaming between two devices seamlessly. The remained of this paper will explain our scheme thoroughly. 2 Two Phases System: Pairing and Streaming As mentioned in the previous section, our service system has device pairing phase and streaming phase. Pairing: The main objective of the first phase is to locate a proper target device, for example, a high performance PC that is capable to decode and display contents with a larger LCD monitor and to negotiate QoS parameters. In this paper, it is called pairing phase. In pairing phase, a portable device will try to search for nearby high performance systems. Along with superior performance, another important factor for pairing is the distance between two devices. As a user wants a better system to enjoy video contained in his/her portable device, the distance between a user and a target system should be considered. Basically, the distance between two devices can be measured with GPS. However, portable multimedia devices may not have a GPS module, but also its accuracy is not fine even if it is applicable.

3 226 J.-H. Jeong, H.-Y. Kim, and E. Kim With the above considerations, our scheme uses ad-hoc communication interfaces [2], [3] instead of infra-structure mode as a pairing interface. Actually, in experiments, we use Bluetooth as a pairing interface. With Bluetooth environment, a user can check target systems physically, and pairing method between devices is well-known. At the last thing of pairing phase, two devices enumerate and do hand-shaking for the streaming connection, that is, QoS parameters (contents bit-rate, playtime, stream- ing protocol, and etc.). Also, in hand-shaking, these two devices need to check RTT (round trip time) by transferring dummy packets. RTT value is used for predicting initial bandwidth for streaming. Streaming: After pairing, two devices are ready to make a connection. Two devices have known the network interface and the address for each. In addition, two devices already negotiated the QoS parameters through the pairing phase, so streaming phase is much simpler. Briefly, when a user signals, the portable device sends acknowledge message to the peer, and then the target system sends a START command to the port- with RTSP and able device. Lastly, the portable device starts pumping contents to the target system RTCP. Searching Negotiating QoS Searching and negotiating Pairing done Registered User presses [start] button Start msg. Streaming req. Streaming Fig. 2. Overview of the proposed service

4 Portable Device-Centric Streaming Service 227 The following is an overview of our streaming steps: 1) Searching nearby devices via ad-hoc wireless network interface, 2) Negotiate device capabilities, 3) Select a candidate, 4) Make a connection supporting large bandwidth for streaming, 5) Streaming contents with RTSP and RTCP. Fig. 2 shows an overview of our service. However, in the contrast to the user s view, streaming is more complicate. A portable device does not have an idea of streaming connection. Moreover, in case of high speed connection coming from portable device, packets pass through several heterogeneous networks such as HSUPA, service carrier network, and wired internet. In these reason, it is difficult for a sender to apply bandwidth adaptation algorithms properly. To cope with the above difficulty, a sender keeps track of RTT. Like TCP-Vegas [6], a sender predicts streaming bandwidth depending on RTT variation. As mentioned previously, since there are many routers for wired/wireless networks, our system need to be simplified as end-to-end system characterized by RTT. If current RTT is smaller than initial RTT resulting from pairing phase, a send expects that the effective bandwidth is broader so that a sender enhances the video quality via contents adaptation; otherwise, the effective bandwidth is narrower. The following equation is a simple decision algorithms based on RTT. RTT φ, φ 1 : φ 1 : otherwise: NO CHANGE In equations, is a RTT rate which means a constant for sensitivity on RTT value, and β 0 1 is another constant for adaptation which means the speed of adaptation. This equation is useful when portable devices stream bandwidth adaptive contents like 3GPP clips. (1) (2) 3 Implementation We implemented our service system in a recent smart phone. We put a short MPEG-4 video into it, and prepared a PC as a target system. We adopted Bluetooth interface as a pairing interface, and adopted EV-DO wireless internet interface as a streaming interface. We programmed two applications for a smart phone and a PC respectively. Application for smart phone has a RTSP/RTCP server module, and application for PC has a RTSP/RTCP client module and MPEG-4 player. When we pressed [PAIRING] button, smart phone searched for nearby devices and then negotiated with PC. After we confirmed the registration, we pressed [START] button. At last, the video contained in a smart phone was displayed in a PC monitor. Actually, in experiments, streaming network interface which bandwidth is broad enough to do streaming is EV-DO interface, so contents is transferred as illustrated in Fig. 4 via the base station of a service carrier. If we configured a wireless network in ad-hoc mode as streaming interface, real streaming path is the same as logical streaming path. This implies that a consumer can enjoy contents rendered on a large LCD monitor without any idea about underlying mechanisms.

5 228 J.-H. Jeong, H.-Y. Kim, and E. Kim Fig. 3. Snapshot of a testing cellular phone in streaming Logical streaming path Internet RTT Real streaming path Base station Fig. 4. Streaming path in experiment 4 Conclusion In this paper, we proposed a portable device-centric streaming service. As our service system has a pairing phase, consumers do not need to know about a target system for contents sharing. Also, consumers can play contents contained in a portable device without transferring physically. Therefore, our service is very useful when consumers want to play contents stored in a portable device, on a high performance system without additional download/upload actions. Besides, decoding and frame scaling processing which are CPU intensive jobs are done in external devices, so the battery lifetime is longer. UPnP [3] also provides similar services with UPnP audio/video streaming server. The main advantage of our scheme over UPnP is on two-level connection. Unlike UPnP, peer-to-peer connection of our scheme is used only to enumerate nearby devic- so es. Actual connection for streaming can be established via infrastructure network, our scheme is more flexible. At last, our scheme is a good example of the usability extension by collaborating nearby devices for complementing the weakness in size of the powerful portable devices [4], [5]. Acknowledgments. This work is supported by the IT R&D program of MKE / IITA [2007-S , A development of cost effective and large scale global internet service solution].

6 Portable Device-Centric Streaming Service 229 References How Bluetooth Technology works. Bluetooth SIG (retrieved, ) 3. UPnP Device Architecture 1.1, 4. Want, R., Pering, T., Danneels, G., Kumar, M., Sundar, M., Light, J.: The Personal Server: Changing the Way We Think about Ubiquitous Computing. In: Borriello, G., Holmquist, L.E. (eds.) UbiComp LNCS, vol. 2498, pp Springer, Heidelberg (2002) 5. Want, R.: Carry Small, Live Large. IEEE Pervasive Computing 6(3), 4 5 (2007) 6. Brakmo, L., Peterson, L.: TCP Vegas: End to End Congestion Avoidance on a Global Internet. IEEE JSAC 13(8), (1995)