Menu and Context Based Interfaces Evaluation for ...

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Procedia Technology 00 (2012) 000–000

CENTERIS 2012 - Conference on ENTERprise Information Systems / HCIST 2012 - International Conference on Health and Social Care Information Systems and Technologies

Menu and Context Based Interfaces Evaluation for Mobile TV Cláudio Freirea,b, Luís Correiaa, Luis Marcelino a,b,*, Catarina Silvaa, Carlos Rabadãoa,b, António Pereiraa,b a

School of Technology and Management, Polytechnic Institute of Leiria, Portugal b INOV Inesc Inovação, Leiria, Portugal

Abstract The dissemination of smartphones and their ability to decode video streams enables users to watch TV possible while on the move. While operators are starting to provide this content type, it is not clear yet how will users adopt these new services. This paper presents a mobile phone application that allows users to watch TV on their mobile phones and a preliminary user interface evaluation for two possible designs: a menu based and a context based interaction. The qualitative results suggest that there is no clear advantage for any of the implemented design alternatives because users not familiar with the application may have a better experience with an interface that presents all options and, as users become more familiar with the application, context menus are not only faster but also reduce the number of errors.

© 2012 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of CENTERIS/HCIST. Keywords: mobile computing; multimedia; user evaluation.

* Corresponding author. Tel.: +351-244-820-300; fax: +351-244-820-310. E-mail address: [email protected].

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1. Introduction Current smartphones and network wireless technologies offer users a significant computational power and bandwidth that enables the creation of new and more demanding services. This work presents the preliminary evaluation of two alternative interfaces for a mobile TV application: an interface that relies on the system menu and another that relies on context menus. These types of interaction are not present when using a traditional remote control and the tests performed aim to clarify which strategy is better for users. Video receiving and decoding is an example of an application that is being pushed by mobile network operators, often as a premium service. However, it is not clear if users will adopt these services not just because of their costs but also because of the social constraints that some people may face when watching TV on a mobile phone at public spaces. Even if these constrains prevail, operators expect users to still watch TV on mobile devices, either at home or at another private environment. Several studies present some of the challenges and requirements associated with Mobile TV [1] [2] or compare the adoption of these services on different countries [3]. Watching TV on a mobile device eliminates a common user interaction metaphor: the remote control. The remote control is a device that has a numerical keypad and two up and down keys, one to switch the TV channel and another to control de volume. Furthermore, a traditional remote has no reference or information about the channels the user can choose. However, most smartphones do not rely on a keypad for interaction and have high quality displays that may show all sort of information about a channel or a show. A user with the mobile device on his hands interacts directly with the application to control which channel to visualize. As this type of interaction breaks away from the remote control metaphor, it is not clear which is the best design approach. To study possible implementation for a TV application, we used an Internet Protocol Television platform that freely supplies a mobile television service, destined to mobile devices. This service intends to be an effective mean of transmitting multimedia contents, with quality, of available Digital Terrestrial Television (DTT) channels, using Digital Video Broadcasting – Terrestrial (DVB-T) [4] devices. Thus, this service allows not just the access to video contents but also permits to navigate through an Electronic TV Guide. The next section presents some related works. Section 3 presents the features of the developed mobile TV application and Section 4 present the two alterative interface designs. Section 5 details the experimental setup, followed by the experimental results and discussion. The final section presents the conclusions and future research directions. 2. Related Work Currently, there are some applications that can receive and decode video stream. Applications for videoon-demand (VoD) often rely on catalogs with the video streams, close to the YouTube solution. Applications that support life video streaming, such as SPB TV (http://www.spbtv.com), offer access to a vast number of channels. Despite of the number of channels, these applications do not reflect the most important public TV channels from several countries. Most channels are news channels and channels with politics contents, while usually recreational contents like movies are left out. The reason for such a discrepancy lies with the copyrights and fees associated with recreational contents. Cable TV providers are also offering video access from mobile devices. For instance, major Portuguese providers, such as MEO (http://www.meo.pt) and ZON (http://www.zon.pt) are now marketing these services. As these services are paid, they are restricted to the providers’ networks and the mobile application is proprietary, their adoption for this study would constraint the type of evaluations to perform.

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Some papers present the design of platforms for broadcast of mobile TV services and discuss possibilities for performance tuning [5]. In this article we include an overview of the implemented application and focus on the interface evaluation. The user interface implementation takes advantage of facilities such as the system menu button and context menus, in opposition to VoD applications that use a contents catalog as the main screen. 3. Proposed solution The implemented Mobile TV system includes a server that receives the DTT and feeds a video stream to mobile applications connected to a local network. In addition, users may rate a program, share comments on a social network or access the electronic program guide, possibly adding a program to their personal favorites list. This solution will use a wireless IPTV architecture [6] [7]. Thereby, we will use a wireless [8] infrastructure, simulating a real network and subsequent clients.

3.1. Network Architecture

Fig. 1. Network infrastructure for the tested IPTV client.

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To implement a service that allows all the enumerated functionalities above, a three-tier network architecture is proposed in Fig. 1. It is divided in three modules:  Server Module – is responsible for feeding the multimedia streams, user registration, information security and other service functionalities;  Network Module – carries out the transportation, with quality of service, of all the data needed for the correct service functioning inside the network infra-structure;  Client Module – allows users to access all the service functionalities from a mobile device. The Server Module is divided in two components: multimedia television content streaming and service support:  The content streaming component is the responsible component for the Digital Terrestrial Television (DTT) signal capture, codification, multimedia content transmission into the network and management of this component. Having regard that the multimedia contents, in one first stage arrive under the form of electromagnetic waves, it is necessary the use of antennas to capture these waves. This antenna is connected to the decoders, to convert the digital signal into multimedia contents, which, after the conclusion of the previous process, send these to the Streaming Server. The streaming server, besides being responsible for sending and receiving multimedia to the Network Core, it also allows the management and monitoring of the service.  The service support component is responsible for handling all the client applications’ requests and ensure communication security, namely the login process, passwords and usernames storage. The Network Module provides the transports of all the information between the server, Internet and the service users. Network equipment, such as routers, connects the other two architecture modules: Server Module and Client Module. The Client Module is composed by a mobile application, allowing users to benefit of all the service functionalities. 3.2. Application Operation When a user starts using the mobile application for the first time, s/he is prompted to set up a service account, after inserting the required credentials, the service checks if the inserted username is unique in the system. If unique, the account is created and the application is restarted with all the service functionalities; if not it launches a warning. The mobile application includes a list of favorite programs, i.e., when the application starts, it checks if the users program television favorites are present in the electronic program guide of the day. If there are any favorites, a notification is launched to notify the user of that fact, by informing at what time these programs will be broadcasted. The main difficulty found during the development of this service, was the bandwidth occupied by the original stream from DTT, roughly 4Mbps per channel. This may pose some problems, considering that the output variation of wireless signal affects the bandwidth available to a mobile device, having as main consequence the degradation of quality service. This also affects the application response time, since the user request (channel visualization), would take longer to be answered, while the goal is to the least possible time. To overcome this problem, the server re-encodes the streaming, reducing the resolution and frame rate of the streamed multimedia contents making it more adequate to reproduce on a smartphone, reducing the required bandwidth and improving the delivery time of video contents (Buchinger, et. al, 2009). Also taking in consideration that the original streaming codec could be incompatible with the Android devices, we’ve defined that the server would encode all streams using the MPEG4 format.

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4. Interface Design One of the factors taken in consideration during the development was to create a simple and intuitive graphic user interface (GUI) to be used in moments of leisure, when users are not willing to navigate through many menus and to spend time learning the application (Buchinger, et. al, 2009). Therefore, users should easily find all the menus and options. To accomplish the above goal two interfaces were designed for the Android platform: one based on system menu and on screen options and another based on context menus. This work presents a comparison between these two interfaces.

Fig. 2. Steps to perform a channel rating using an interface based on system menu and on screen options.

The first interface, depicted in Fig. 2, has several intermediate screens for a given operation. The user navigates thought them and use the menu button of the device to access a specific operation. In this design even secondary operations are present at the screen to improve the user perception of available functionalities. The main screen shows the most important information about the current program being broadcasted by a given channel, duration, program name and rating. The users can visualize the multimedia contents by pressing the play button. When the user presses the menu button of the device, more options are showed, enabling the execution of other service functionalities.

. Fig. 3. Steps to perform a channel rating using an interface based on context menus.

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In the interface based on context menus, presented in Fig. 3, the existing intermediate screens were removed, reducing the navigation steps through the screens. On the Android platform, context menus are accessed through a long press on the relevant item The design presented in Fig. 3 has a main screen with the most important information about the current program being broadcasted by the channels, program name, rating and the next two programs. The users can visualize the multimedia contents by selecting in the context menu “Watch Channel” (“Ver canal”). The use of context menus resulted in a reduction from 5 to 3 screens to perform a given operation from our first design. Because it is not clear that this change will provide a better user experience we performed a preliminary user interface evaluation. 5. Experimental setup The main goal of experiments was to evaluate the user performance with each interface approach:  Menu based interaction: interface that uses the system menu and on screen options;  Context based interaction: interface that takes advantage of context menus. In these experiments we had the participation of 18 users, 9 women and 9 men, aged between 17 and 40 years old. From these participants 13 had previous experience with smartphones, 11 of which with the Android platform. Users with no previous experience with the Android platform had a brief introduction on the main usability features. To perform the tests, a scenario was simulated and the participants were informed about the purpose of the application. For the tests different mobile devices were used, with different screen resolutions, more specifically, Samsung Galaxy Gio, Samsung Galaxy S and HTC Desire Z. Before each test, the devices were configured to have connectivity with the server and Internet. Participants were asked to execute a set of tasks typically performed in a real environment. Each task was executed separately, to avoid compromising the next. The defined tasks were:  Task 1: Visualize the live TV program on channel SIC;  Task 2: Browse the TV Guide of channel RTP1, get the details of the last show of the current day from RTP1 and check it as a favorite;  Task 3: rate the current program/show of RTP1 channel with five stars,  Task 4: view the favorite shows and deletes them all. To watch the channel SIC (Task 1), users on the first interface approach had to select the channel by pressing the arrow button next to the channel image. Has the SIC is the third channel the button had to be pushed twice and then users had to press the “Play” button. For the context menu approach, users had to do a long press on the third row of the channels list and select “Watch channel” (“Ver canal”). To browse the TV guide and get details for the last show of that day, users of the interface with on screen and menu options had to select the TV guide from the menu, select the channel from the arrow buttons and slide down until the desired time. Users of the context menu approach had to long press on the channel entry and select the “TV guide” option. To rate the program, users from each interface had to follow the path illustrated in Figs. 2 and 3 from the previous section. To delete all favorite programs users had to select all the existing favorites and delete them. 6. Experimental Results and Evaluation The metrics used to evaluate the user experience included the time to execute each task and the number of errors during its execution.

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All users executed Task 1 under 1 minute with no errors and, therefore these results are not included in the following graphs to simplify their interpretation. Fig. 4 shows the execution times for Tasks 2, 3 and 4 for each interface design. Navigation on the TV guide was faster with more screens than with context menus. However, the rating of a TV show was faster with context menus.

Fig. 4. Time to execute Tasks 2, 3 and 4.

Fig. 5 enumerates users’ errors for Tasks 2, 3 and 4. The interface based on screen options and system menu resulted in fewer errors to choose the channel and show on the TV guide but performed worse on rating the show. These results are in line with the ones presented above.

Fig. 5. Number of errors to execute Tasks 2, 3 and 4.

To filter possible problems of non-familiarity with the platform, Fig. 6 presents the time to execute Tasks 2, 3 and 4 by Android users. For these users, browsing the TV guide on the first interface approach was fast and presented no errors while rating a show was more problematic. It is noteworthy that all tasks from these users on both interface approaches had no errors or had a single error from a single user while Task 3 for the menu based interface had multiple users with multiple errors.

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Fig. 6. Execution times for Tasks 2, 3 and 4 by Android users.

To evaluate whether users of the Android platform had an advantage over the users with no prior experience, we rearranged results. Fig. 7 presents the time to execute Tasks 2, 3 and 4 for Android users and for non-Android users. The results show that Android users performed better on navigating the TV guide but performed slightly worse on the rating of the show.

Fig. 7. Execution times for Tasks 2, 3 and 4 grouped by users experience.

7. Discussion The results above show a satisfactory level of success for the interaction with both interface approaches. All users using any of the interface approaches were able to choose the channel under one minute and with no errors. Both time and number of errors metrics are consistent for the results of both interfaces. Navigating the TV guide (Task 2) was faster and less error prone with and interface that presented all option on screen and that would use the menu button. However, rating a TV show (Task 3) was faster and without errors with an interface based on context menus. It is interesting to note that Task 3 is an extension of Task 2, because to rate a show one must select it on the guide first. The most likely explanation to these results is that Task 2 trained users to perform Task 3. Therefore, even though users of the context menu interface struggled more on the first assignment, they learned how to execute Task 3 more efficiently. The interpretation of the experiment results with users grouped by their experience also suggests that Task 2 trained users for Task 3. Users with no previous Android experience are the ones who may benefit the most from some training. Comparing the times from Task 2 and Task 3 it is noticeable that Task 3 was faster to execute even though was more complex than Task 2. The same did not happen with Android users, possibly

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because their interaction with the application reflects their usual interaction style. This may explain why Android users did a fast and flawless Task 2 but struggled with Task 3. The experiment results suggest that there is no clear solution for an interface design of a mobile TV application. Users not familiar with the application may have a better experience with an interface that presents all options. However, as users become more familiar with the application, context menus are not only faster but also reduce the number of errors. Therefore we propose that mobile TV applications should have both interaction styles: channels lists may be selected to show a screen with more information and features or may be used with context menus to jump to the desired feature. 8. Conclusions and Future Work This paper presents an application and architecture that allows a television service to be supplied for Android mobile devices, thus enabling users to visualize their favorite programs anytime anywhere, in a simple and comfortable manner. The system uses a Local Area Network to distribute video content. For this mobile TV application, we implemented two alternative graphical user interfaces: one based on system menu and on screen options and another based on context menus. These interfaces require distinct interaction styles and we aimed to evaluate which was better for this type of application. The results from the executed tests suggest that users learn and adapt to the application user interface. Novice users may not be familiar with context menus (which are not present, for example, in the iOS) and, therefore, having the application options and features visible on different screens may help them. But as they learn about the application they perform better, both in terms of time and number of errors, using context menus as a shortcut to the desired feature. For this reason we find that a mobile TV application should have both interaction styles. This research may be further extended to evaluate the user evaluation in different usage context, for example comparing the application use in noisy and calm environments, or while the user is still or on the move. Another interesting study is to assess how do users interact with the mobile TV application that integrates with social network platforms. TV shows may now have a life audience that expresses itself.

Acknowledgements We would like to thank José Rodrigues and Rui Sábio for their willingness and support that made this research and implementation possible.

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