The Linux4.TV Set-Top Box Open Source Project

Here are the details on the new Linux4.TV development kit we're giving away in our development contest. Find out about MPEG playback, video capture, HTML-based interface and more.

Linux is being used in an increasing array of devices outside its origins of desktop and server systems. Enhanced multimedia capabilities, combined with continuing development and support for advanced state-of-the-art hardware, have enabled Linux to be used in TVs and set-top boxes. In this article, I describe a project that I've been involved with for the past year: implementing an open-source, Linux-based, set-top box platform, known as the Linux4.TV Project ( Century Embedded Technologies and National Semiconductor Corporation have collaborated to produce Linux4.TV, a completely open-source, open-architecture, set-top box platform with support for digital and audio tuners, DVD, streaming video and other features.

System Architecture

National's Geode SP1SC10 demonstration platform was used as the hardware platform for the first implementation. The Geode SP1SC10 platform CPU is the 266MHz National Geode SC1200, featuring an x86-compatible 32-bit instruction set, MMX support, 2-D graphics acceleration, an integrated NTSC/PAL controller and a CCIR-656-compatible video input port for full-screen video display. The motherboard also hosts a Philips SAA7114 chip for analog NTSC and S-Video input decoding, as well as a Sigma Designs EM8400 chip for real-time hardware decoding of MPEG-2 digital video streams. A block diagram of the SC1200 CPU is shown in Figure 1, and the SP1SC10 platform architecture in Figure 2.

Figure 1. National Semiconductor Geode SC1200 Architecture

This system design allows various analog and digital video inputs to be decoded and routed into the video input processor component of the CPU, where the video data can be scaled, alpha-blended and merged with graphical data from standard framebuffer memory. In this way, windowing systems, widget sets, browsers and other application software can run normally, with the graphics data output combined in real time with the desired video stream by the CPU and other components. The system's software design takes advantage of this architecture allowing applications to be integrated with few, if any, modifications to work with the video subsystem.

Figure 2. Geode STB Platform Architecture

National has developed a lower-cost development platform to replace SP1SC10, allowing more people access to STB technology for evaluation and development. The new board, available later this winter, will be completely open, with the full schematics and technical descriptions available on Linux4.TV. Two PCI-compatible slots also will be included, allowing easy customization of the system with additional chips, such as the Geode CS13x0 multimedia coprocessors.

In addition, several other vendors have platforms based on the Geode SC1200, and porting of the Linux4.TV code is in process. These vendors include VT Media Technologies and Cocom Group. Advantages of third-party vendors include a variety of form factors for set-top box deployment.

Software Architecture

National Semiconductor has invested a large amount of time and money into the development of software technologies running on Geode processors and the SP1SC10 platform and is interested in making these technologies available to the Open Source community. National's Open Source philosophy is represented well by the Linux4.TV Project, in that all of the software running on the demonstration platform is available on the Linux4.TV site, with complete API specifications and documentation.

There are four major layers in the software architecture, as shown in Figure 3: kernel and device driver, Video Middleware, windowing system and WebMedia/applications layers. National Semiconductor contributed the kernel drivers and Video Middleware layers, with Century contributing the WebMedia user interface, windowing system, applications layer and overall distribution. The complete distribution is available both as a bootable system image and as a complete source tree. Following are more technical descriptions of each layer.

Figure 3. Linux4.TV Software Architecture


White Paper
Linux Management with Red Hat Satellite: Measuring Business Impact and ROI

Linux has become a key foundation for supporting today's rapidly growing IT environments. Linux is being used to deploy business applications and databases, trading on its reputation as a low-cost operating environment. For many IT organizations, Linux is a mainstay for deploying Web servers and has evolved from handling basic file, print, and utility workloads to running mission-critical applications and databases, physically, virtually, and in the cloud. As Linux grows in importance in terms of value to the business, managing Linux environments to high standards of service quality — availability, security, and performance — becomes an essential requirement for business success.

Learn More

Sponsored by Red Hat

White Paper
Private PaaS for the Agile Enterprise

If you already use virtualized infrastructure, you are well on your way to leveraging the power of the cloud. Virtualization offers the promise of limitless resources, but how do you manage that scalability when your DevOps team doesn’t scale? In today’s hypercompetitive markets, fast results can make a difference between leading the pack vs. obsolescence. Organizations need more benefits from cloud computing than just raw resources. They need agility, flexibility, convenience, ROI, and control.

Stackato private Platform-as-a-Service technology from ActiveState extends your private cloud infrastructure by creating a private PaaS to provide on-demand availability, flexibility, control, and ultimately, faster time-to-market for your enterprise.

Learn More

Sponsored by ActiveState