4. Playback Interface
We implement an MMNail playback interface in Flash that is compatible with smart phones running the Pocket PC OS 2003 and Windows Mobile operating systems. First a general document browser interface that displays a conventional thumbnail of the first page of each document is shown in Figure 5.a. When a user selects a document thumbnail the MMNail visualization for the selected document is displayed in the interface given in Figure 5.b. The user has control over playback with a control bar, which he can use to start, stop, go backward and forward in the MMNail timeline. In addition to the control bar, the user can also use the keypad of the device to pause and play MMNails and to move to the beginning of the previous or next MMNail animation segment. This way, users have more control over the playback. They are able to skip less interesting parts and spend more time on more interesting sections.
Figure 5. Interface for (a) document browsing and (b) document viewing.
5. Example Multimedia Thumbnails
In this section we present examples of automatically generated Multimedia Thumbnails for different time durations. The MMNail example shown in Figure 6 is generated by setting the time duration in the optimizer to be 40 seconds. The visual channel is taken by document pages, zooming into the title, some sections, and many figures. The audio channel is occupied by document title, section headings, and figure captions. Figure 7 shows an automatically generated MMNail of the same document with a 10 second duration constraint. Because this duration is quite short, there is only time to zoom into the title of the document. For the rest of the pages in the document only the page thumbnails are selected to be displayed. The audio channel is mostly occupied by the title and the keywords. More MMNail examples can be downloaded at [26].
Figure 6. Example of a 40 second Multimedia Thumbnail.
For the same document and the same durations, MMNail examples are also generated with time scalability constraint as described in Section 3.3.1. In this case, the 40-second MMNail remains unchanged since presented content is selected from all document elements. On the other hand, the contents of the 10-second MMNail slightly changes since the selection of document elements is based on the contents of the 40-second MMNail instead of the whole document. As can be seen from Figure 7, the visual channel of the time-scalable MMNail remains the same, but the audio channel does not contain some of the previously included document elements, such as most of the keywords.
Figure 6. Example of a 10 second Multimedia Thumbnail.
