WinBook Tech Article
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Subject: Zoomed Video FAQ
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Tech Article Number: WBTA00120754

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Introduction

The Zoomed Video port (ZV Port) offers an attractive alternative to the traditional video input methods. It offers a low-cost, simple multimedia solution for the user. The notebook computer now has new technology that allows portables to evolve at a pace that is on par with desktop machines by providing multimedia solutions that fit into a PC Card form factor.

The Zoomed Video specification provides for an inexpensive, full frame-rate video display channel for applications like MPEG decoders for movies and games, TV tuners, live video input and video capture.

ZV Port allows video data on a PC Card to be transferred directly into the VGA frame buffer.

What Is the ZV Port?

The ZV Port is a point to point uni-directional video bus between a PC Card host adapter and a VGA controller. The ZV port complies with CCIR601 timing to allow NTSC decoders to deliver real-time digital video straight into the VGA frame buffer from a PC Card via the PC Card host adapter and the ZV Port.

How does it work?

The PC Card host adapter has a special multimedia mode configuration. In this mode the PC Card connector pin assignments change. The ZV Port proposal prescribes how a ZV Port PC Card ZV Card transitions from its initial PC Card memory mode into ZV Port mode. The PC Card Standard specifies both the hardware interface and the software interface to a ZV Port PC Card ZV Card, to ensure compatibility with other PC Cards. The multimedia-mode PC Card is required to meet all existing power-on and hot plug-in requirements.

What can I use Zoomed Video for?

The following examples illustrate how the ZV Port supplements the PCI bus utilization in multimedia applications.

Live Video from a real-time source (Video Phone)

One application for ZV is videophones. In this type of application, 60 fields of interlaced video have to be transported in an uninterrupted manner from a source (i.e., video encoder) to a destination (i.e., the display screen) in a system.

In order for this to occur, a contingency issue must first be resolved. A system with a single PCI bus can handle live video, but in practice, it is difficult to ensure that enough bandwidth is available. The only way to guarantee that there will be no "video tearing" at the destination or display point is to have enough memory at the source point to buffer at least one full frame of video data (a little over a 1/2 megabyte of memory).

One way to guarantee uninterrupted 30 frames per second video at the destination point is with a dedicated bus like ZV Port. With a dedicated bus, the video is directly connected to the display controller, which enables the video stream to flow uninterrupted from the source to the destination, and eliminates the need to buffer the video stream at the source.

Video capture (AVI MOV MPEG)

Another application for Zoomed Video is capturing video to disk. To capture and view the video, the video source controller must bus master the same video asynchronously to two different destinations- the display screen and the disk or storage device. This is expensive and requires a PCI bus mastering controller at the source. With ZV Port, a PCI bus master is not required. The video data is supplied via the ZV Port to the display controller where it is displayed. The capture-to-disk operation is then controlled by the CPU, which pulls the data out of the display frame buffer and sends it to the storage device. This is a true "what you see is what you capture" operation.

MPEG-based games

MPEG-based games place more stress on a system than MPEG playback. A PCI bus can handle MPEG playback without any strain, but MPEG-based games require the system to keep a MPEG decoded video stream flowing to the display, render 3-D graphics images, and mix them with the video at some point between the MPEG decoder and the display screen. MPEG-based games will evince the demand for a supplementary video bus to be in the system. A MPEG decoder streams the video straight into the frame buffer via the ZV Port by giving the CPU almost 100% utilization of the PCI bus for rendering the graphics into the same frame buffer. The graphics engine has the responsibility to mix the two streams and send them to the display.

What software is ZV composed of?

The PCMCIA components are: 1) Socket Services, which is used to manage the mode-switching in the PC Card host adapter; and 2) Card Services, which is used to detect and enable ZV Port PC Cards using the ZV Port interface.

A new piece of software is required to control ZV Port. This is the Video Port Manager (VPM) display driver.

Conclusion

The Zoomed Video Port offers an attractive alternative to traditional video input methods and provides an inexpensive, full frame-rate video display channel for applications like MPEG decoders for movies and games, TV tuners, live video input and video capture. With the ZV Port, the mobile user now has a broad range of options to choose from in adding multimedia to their notebook configuration, and notebook designers can reduce the cost of their notebooks.


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