Mobile Blog: Video, Media, Augmented Reality, Rich Media, IVVR

photo credit: marcopako 

One step backwards: Windows Mobile 7 should lack Adobe Flash support. We are all awaiting Adobe Flash 10.1 for mobiles which hopefully reduces cross-platform development costs. But (maybe) Microsoft will follow Apple’s strategy by restricting Adobe Flash support on WM7 devices. Read more on mobiletechworld.com

First of all, Windows Mobile is so close to Windows for desktop PCs that you might expect to install some of the applications you know from your desktop on your mobile. Media Player, Outlook and Office Mobile, including Word, Excel, PowerPoint and so on -it’s all included in WM6.5 Pro. What’s left? A good mobile media player! WM6.5 Media Player doesn’t like my DivX movies and some MP4 files. For DivX there is a solution: DivX Mobile Player for Windows Mobile. Note: Although DivX Mobile supports the latest DivX codec features, your mobile processor is limiting your mobile video experience. I’ve downloaded a DivX movie from the Internet and tried it on my phone: The sound was fine, but the video was choppy. After some experiments I saw, that a video bit rate above about 300 kbit/s is causing problems. For the technical folks: It is not really the bit rate, but the complexity of the encoding that makes the mobile processor go nuts. The higher the bit rate and the higher the complexity, the more likely the video, or even the sound will be choppy.

DivX Mobile Player is for free, but it doesn’t support native MP4 containers with h.264. Therefore I bought CorePlayer Mobile for $30. It’s nice, but not really worth 30 USD. It doesn’t offer as many codecs as VLC or mplayer, and it’s user interface is too desktop-alike. CorePlayer Mobile has a lot of submenus; you need about 4 clicks to activate the fullscreen mode! Unfortunately, VLC for Windows Mobile isn’t available yet: VLC forum.

photo credit: papalars

Did you already sign up for GSMA world congress in Barcelona 15-18 February 2010? Let’s meet: http://www.mobileworldcongress.com

photo credit: qthomasbower

Applications cannot enlarge a small screen visually, but they can implement techniques that virtually increase the size of the display. One way is providing horizontal or vertical scrolling of the user interface to make new information visible while hiding other content. Another idea is a Peephole display that shows a different portion of a bigger picture when the phone is moved to the left, right, up or down. Unfortunately, neither approach works well with IVVR (Interactive Voice & Video Response). There are no positional sensors usable with 3G-324M, and scrolling requires fast screen updates with the ability to hold a key as long as the user wants to scroll. High delays in the current 3G-324M deployment and lack of transmitting the information that a key is hold for a time prevent the implementation of such features. However, applications can have multiple layers, such as a deck of cards that can be shown or hidden depending on the user’s selection. Furthermore, designs can take advantage of the media- streaming capabilities and multimodal information channels by providing some information using speech output, some with pictures or text, and others by using video sequences.

Mobile users demand visually attractive user interfaces that are clearly readable and intuitive to use. Application flow design is beyond the scope of this thesis, and every application and game will have its own characteristics to model and challenges to overcome. Nevertheless, some basic guidelines for slide-based IVVR applications can be given.

Slide-based applications such as IVR (Interactive Voice Response) Supplements shown in Figure 6 are best visually designed using pixel-based image editors such as Adobe Photoshop. The video codecs used in 3G-324M work in the YUV420 colour space, and the target image size is 176 x 144 pixels (QCIF (Quarter Common Intermediate Format)). With basic understanding of chroma-subsampling and how spatial and temporal compression in video codecs works, designers can create slides that will compress well while maintaining sharpness where essential. A precondition is to align the slide’s layout to a raster of 16×16 pixels with one subdivision (8×8) as seen in the figure below:

Template with 16x16 grid

To ensure best readability despite video compression, designers should use sans-serif fonts. Moreover, the font colour and the background colour should have a high difference in luminance. The human eye can distinguish difference in luminance easier than in colour; this fact is used by video compressors and is the foundation of chroma subsampling. For instance, a white font on a light yellow background is already hardly readable without compression. After compression, however, with only half of information available for colour differences when using YUV420, the font will not be distinguishable from the background. The author’s experiments showed that especially Microsoft’s Calibri font creates a nice typeface even after compression. Calibri’s subtly rounded stems and corners are perfect for H.263 DCT-based compressors that create smooth edges. Note that the minimum font size is 18px when lossy compressed in order to be readable for mobile users. We can only hope that next-generation IVVR applications can use T.140 or similar ways to transmit ASCII-text directly, making readability considerations obsolete.

Video call set-up times are generally between 1 to 5 seconds (1-second call set-up when using MONA specified in H.324 Annex K.) independently of the IVVR (Interactive Voice & Video Response) application one is going to use, which is sometimes faster than the initialisation process of complex J2ME (Java 2 Micro Edition) applications. This makes quick on-the-go lookup or entry of information pleasant. However, what happens when the caller needs to interrupt a gaming session or the call is interrupted because of missing network coverage or exceeded battery life? Games should enable users to start and stop with breaks in between, since the time they have to spend may be brief. Mobile games are used especially to pass time for just a couple of minutes or even seconds when waiting for the bus, riding the subway, or to relieve boredom during TV commercials. Therefore, all mobile applications need to apply ways to interrupt a session and quickly resume to the last state as the user desires. This requirement also applies to IVVR applications. As application and user data of IVVR programs can be completely stored on the server-side, there are no limitations to auto-save program states or record the user’s actions. With the caller’s unique phone number as an identifier, it is easy to develop resumable applications.