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Advanced DVD Players With MPEG-4 ı Part III: The Software Perspective
by Ken Lowe, VP business development and corporate communications, Sigma Designs, Inc.

In this third and final article of our series discussing advanced DVD players, we will focus on the complexities and programming considerations faced by the software team. The series opened with a discussion of the expanded role of DVD players driven by the proliferation of downloaded formats, especially MPEG-4, and the improvement of the visual experience. As these advanced DVD players head toward a generation of multi-function, multi-format, high definition and graphically-driven audio/video appliances, it creates an expanded set of parameters that both hardware designers and software programmers must deal.

Towards A Dramatically New User Interface
Todayıs typical DVD player is a plug-and-play device, requiring little more than disc insertion and a single button to initiate playback from fixed format DVD or CD media. Until today, there have been few media formats, and the mechanism for recognition and selection has been clear. Inserting a DVD disc triggered the use of DVD-video format, while inserting a CD disc meant differentiating between a VCD and CD-audio formatted disc and playing accordingly. However, as we move into the next generation of DVD players, users expect to initiate play for a variety of content types, mixed on a single disc, arriving as either a DVD or CD medium from published or downloaded content. For the purposes of this article, we will focus on the flexibility and development challenges of supporting a software browser to enable viewing and playback from any combination of formats and media.

Table 1 lists the primary format and media requirements for the next generation of DVD players, supporting the widest range of currently available content. As is evident, the user interface must allow browsing for either CD or DVD type discs and enable a selection from several formats of video, audio and still images. Each interface for finding media is different, and the viewable information (such as playlists), music metadata and folders with photos or videos, varies depending on the source of that media. Given the lack of standards for navigation, many vendors are developing their own navigation software and user interface.

TABLE 1: Supported Media and Formats

In a related trend, Microsoft, Panasonic and Fujifilm jointly announced HighM.A.T. (High-performance Media Access Technology), designed to significantly improve interoperability for digital media content between PCs and popular electronic devices, such as CD players, car stereos and living room DVD devices. HighM.A.T. is a convenient way to move digital media from a PC to consumer electronics devices, providing a consistent way for CD and DVD players to read data. Additionally, it promises to increase startup times for data CDs and other physical formats, making navigation across a broad range of consumer electronics devices ı including car stereos, DVD players and CD players ı consistent and easy.

Structuring the Disc Browser
Creating an application environment to support a disc browser is relatively straightforward and depends primarily on the breadth of functionality to be supported. A simple disc browser could be implemented directly, without a real operating system. However, given the trend toward Web-enabled DVD players that can browse and download content directly to a local hard drive, it makes sense to begin with an extensible environment and optional network stack that can serve an online environment and Web browser. Towards that goal, a small embedded operating system should be employed with an image size of less than 1MB.

On top of the operating system, a disc browser application would be created to provide the functional control of the DVD player, including user interface and media navigation. A menu-driven user interface will accept user selections and call a set of bit-maps to provide graphical interaction with the playlist, as well as control playback with buttons for play, pause, search, and others. The application would also call the appropriate media navigation module, depending on the content involved, including standard navigation modules for DVD video, VideoCD, and audioCD, and custom navigation modules for additional video, audio and image files to be supported.

Supporting the application are lower layers of software, typically operating in the kernel mode of the operating system built to communicate with the hardware. An MPEG hardware driver would be created that manages the decoding of the audio or video streams. Likewise, a remote control hardware driver would receive user-initiated inputs and map them into functional equivalents. For the DVD drive itself, the reading, header information and sector location data should conform to ISO 9660.

The memory image of the entire software environment is indicated in Figure 1. As described, the largest portion is taken up by the operating system at something below 1MB, depending on installed services. The next largest portion is the navigation modules, where DVD navigation can be expected to take up nearly 300kB, while the remaining modules could account for around 200kB. Next, the hardware (MPEG) driver would account for approximately 250kB, while the remote control driver would account for a minor portion. Finally, the browser application would likely consume around 300kB, the majority of which being user interface bit maps (around 200kB worth).

Figure 1: Memory image of an advanced DVD player based on a disc browser

An Example Implementation
Sigma Designs is a manufacturer that has implemented a DVD browser in support of an advanced DVD decoder chipset Sigma started with an embedded Linux operating system, configured specifically for usage as shown in Figure 2. Running in the Linux user space, the browser application provides the functional control of the DVD player, including user interface, media navigation and playback control. Just below, the MPEG driver and remote control driver in the kernel space provide the essential link to the DVD decoder chip and remote control device, respectively. As implemented, Sigmaıs code creates a memory image of approximately 2MB in Flash. By choosing to implement the software in this fashion, Sigma is providing an extensible foundation that will support additional functions, such as a Web browser, network connectivity and other advanced features.

Figure 2: Sigma Designsı software architecture for an advanced DVD player reference design

As DVD players take on more advanced features, their architecture, chipsets and cost will continue to lead to convergence with other set-top appliances. Ultimately, consumer demand will decide what is the right price/performance trade-off, and what form of convergence product provides the best utility. For now, DVD players are destined to become the center of playback for virtually all purchased, downloaded and originally created audio/visual formats.

Author's Bio
Ken Lowe is currently the vice president of business development and corporate communications for Sigma Designs, Inc. His role in this position includes developing strategic partner relationships, directing public and investor relations, directing trade show and special promotions and managing market research. Lowe holds a BSEE degree from California Polytechnic State University at San Luis Obispo, Calif.

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