How accessDTV Works

The excitement around digital television (DTV) has been growing steadily for several years. If you have been to any of the major electronics stores recently, you have probably noticed shelves filled with digital television sets.

At the same time, television stations have been quietly launching their digital transmitters. The stations and the networks have been outfitting their studios and trucks with the equipment they need to shoot, record and edit with purely digital signals. Almost all prime-time shows and sporting events are now digital.


In most major cities, you can receive digital broadcasts. For example, in San Jose, CA, you can receive about a dozen DTV broadcasts. Even in a relatively small city like Raleigh, NC, you can receive four stations. More than 100 million Americans are able to receive at least one digital broadcast, but far fewer than a million currently do. The main barrier has been the price and complexity of home DTV equipment.

In this article, we will talk about the inexpensive PCI card for your computer that allows you to instantly start experiencing everything that DTV has to offer on your computer monitor.



Access DTV lets you watch TV on a monitor like this one.
Access DTV lets you watch TV on a monitor like this one.

The accessDTV card has a number of interesting features:

  • It allows you to receive all of the DTV stations in your area on your PC.
  • It allows you to display the picture you receive in a window on your computer monitor's screen, full on your computer monitor's screen or externally on a DTV display.
  • It provides personal video recording that allows you to record DTV broadcasts onto your hard disk for later viewing.
  • It provides a service that gives you a program guide, listings for digital broadcasts in your area and links to content-related Web sites.

DTV technology and programming is advancing quickly, and this card lets you experience it all.


If you have read How Digital Television Works, then you are familiar with the world of DTV. Here is a quick summary of the important points:

  • Broadcasters in your area have each been allocated a new channel for their DTV broadcasts.
  • The broadcasters each transmit a 19.39-Mbps stream of digital data. This signal contains television programs compressed using the MPEG-2 compression system.

DTV shows can be broadcast at several different resolutions:

  • 480p - The picture is 704x480 scan lines sent at 60 complete frames per second.
  • 720p - The picture is 1280x720 scan lines sent at 60 complete frames per second.
  • 1080i - The picture is 1920x1080 scan lines sent at 60 interlaced frames per second (30 complete frames per second).
  • Broadcasters can transmit either a single 1080i high-definition channel that consumes the entire 19.39-Mbps stream, or several different sub-channels by encoding multiple programs at 480p resolution and lower bit rates.

For example, the DTV station 53 can have sub-channels named 53.1, 53.2 and 53.3. accessDTV can record and play back the sub-channels.

The accessDTV Digital­ Media Receiver Solution consists of hardware and software. The hardware is a PCI card that you install inside your PC. The software controls the card and allows you to tune in and view DTV broadcasts in your area, using either your computer monitor or an external HDTV display.

Components on the accessDTV board
Components on the accessDTV board

The following figure shows you a block diagram of the components on the accessDTV PCI card:

The tuner receives the signal from the antenna and tunes in a single channel. The demodulator retrieves the 19.39-Mbps digital stream from the channel. The MPEG decoder decompresses the MPEG encoding and separates subchannels. The signal then goes to either the connectors on the board that connect to a DTV monitor, or to the computer's video card directly. MPEG signals and sound information can go through the PCI bus to the hard disk and sound card, respectively.

The two most important components on the accessDTV card are:

  • The digital tuner
  • The MPEG-2 decoding system

By connecting a standard UHF/VHF antenna to the accessDTV card, you can tune in any of the 69 DTV channels. (In a typical city, there will be from three to 10 DTV channels on the air.) The tuner pulls the 19.39-Mbps data stream off the channel you choose.

The MPEG-2 decoder circuit decodes this data stream and separates any sub-channels so that you can view them. This is the most important part of the card because it offloads all of the MPEG-2 decoding from your CPU.

The 19.39-Mbps stream is so complex that it would totally consume a Pentium 4 processor running at 1.5 gigahertz (GHz). The accessDTV card contains a custom processor specifically tuned for MPEG-2 decoding. With the accessDTV card handling decompression, only about 5 percent of your computer's CPU power is spent displaying the digital image on the screen. From your computer monitor, you can watch a DTV broadcast in one window and do anything you want in other windows without even knowing that the card is running.

The card also contains a cable-ready and NTSC off-the-air-ready analog tuner. You can connect the coax from your cable system or a standard TV antenna and receive analog channels 2 through 83 as you would on any normal TV. You can also view these channels in a window on your computer screen.

The accessDTV card comes with a collection of connectors that you use to accept video input and generate audio/video output. This diagram shows you the connectors:

Here's what these connectors do:

  • Analog in - This accepts analog video input. The input can be an analog-TV antenna, a feed from the cable company, or a channel-3 input from something like a VCR or DVD player.
  • Digital in - This accepts digital video input. Typically, this would be the Yagi antenna collecting the digital broadcasts in your community, but it could also be a cable from a digital satellite receiver.
  • Dolby Digital Surround Sound (AC-3) output - This is the output for digital sound. Typically, you would connect this to your 5.1-channel home-theater sound system (see How Home Theater Works).
  • PC Video passthru in
  • Video output - This looks like a standard VGA connector. You can use a cable to connect this to the component video input of any supported digital display, including DTV sets. In this case, the card acts as the display's digital receiver.

There are two typical ways that you might connect the card in your home: for computer-only viewing or for HDTV-display viewing.

Computer-only Viewing

Let's say that you do not own an HDTV display right now, and you simply want to watch HDTV broadcasts on your computer's monitor. You would do the following:

  1. Connect a standard UHF/VHF antenna to the digital video input on the accessDTV card.
  2. Connect the cable that comes with the accessDTV card between the card and your normal video card.
  3. Run the accessDTV application, choose your channel and enjoy the broadcast. You can watch DTV in a window or full-screen on your computer monitor.

HDTV-display Viewing

Let's say that you own an HDTV display and a home-theater sound system, and you want to watch HDTV broadcasts on your HDTV display. This means that you want to use your accessDTV card as the digital receiver for your HDTV display. You would do the following:

  1. Connect a standard DTV antenna to the digital video input on the accessDTV card.
  2. Connect the cable that comes with the accessDTV card between the card and your normal video card.
  3. Connect the external HDTV display to the XVGA connector on the accessDTV card using a standard XVGA-to-RGB cable.
  4. Connect the home-theater sound system to the serial-digital output on the accessDTV card.
  5. Run the accessDTV application, choose your channel and enjoy the broadcast. You can watch DTV on the external HDTV display, or in a window or full screen on your computer monitor.

A typical screen shot when using the accessDTV board
A typical screen shot when using the accessDTV board

The accessDTV card is a very interesting product because, when combined with its software, it can do many different things.

The Basic Idea

The basic idea behind the accessDTV card/software combination is that, once installed in your computer, it allows you to watch DTV on your computer's monitor. There is nothing else to buy, so this is definitely the least expensive way ever to watch DTV in your home. And, it turns out that in full-screen mode, this is a good way to watch DTV -- standard computer monitors create a high-quality display that really shows off the clarity of DTV.

Because the card does all the heavy lifting when it comes to decoding both digital- and analog-TV streams, the card has almost no impact on the performance of your machine. You can have a DTV broadcast displaying in a window on your screen and do anything else you would normally do with your computer.

In a sense, the DTV window on your monitor is just like watching a streaming video on a Web site. The difference is that the DTV window is:

  • Incredibly clear - It is receiving data at 19.39 Mbps. The maximum speed you can get off the Web is perhaps a 300-kilobit per second (Kbps) streaming connection, and 100 Kbps is much more typical. The HDTV signal is about 200 times faster than a typical streaming connection, and it is never interrupted by network delays.
  • Non-disruptive - When you watch a streaming media presentation off the Web, the act of streaming the data into your machine consumes your entire Internet connection. It also consumes a lot of CPU power decoding the signal. Your HDTV window consumes zero network bandwidth. The card does all the digital decoding, so your computer is free of this task and able to do other things.

In other words, the accessDTV card gives you the best streaming media you have ever seen! It also gives you a new way to use your computer. Typically, you use your computer and watch TV in different rooms. Now, the two activities are integrated on your computer -- you can watch DTV in one window while browsing the Internet or working on a presentation in another window.

An additional benefit to viewing DTV on your computer is that some broadcasters are sending Web pages alongside shows. Some DTV stations broadcast Web content on a 1- or 2-Mbps sub-channel, and you can view it in a browser on your computer screen. This is a new idea that is waiting for clear standards and patterns, but some broadcasters are trying it now.

DTV Receiver

The accessDTV in your computer can turn your computer into a great DTV receiver. You can plug your HDTV display and home-theater sound system into the card, and the card will send out exactly the same signals that any other DTV receiver does. This can save you the cost of purchasing a separate DTV receiver. This receiver will also be more versatile than other receivers on the market today because...

Video Recorder

One of the most interesting parts of the accessDTV software is the Personal Video Recording, or digital video recorder, that comes with it. You can program the recorder to record any channel, and the card will stream an entire 19.39-Mbps channel to your hard disk. Because it is the entire channel, this means that all sub-channels and any data streams within the channel are all recorded, and the card can later play them back as though it were receiving the broadcast signal. The video recorder consumes about 9 gigabytes (GB) of disk space every hour, so an inexpensive 60-GB hard disk holds about seven hours of video.

Personal Program Guide

The accessDTV card comes with a program guide service that lets you see all of the programs in your area and tune them in. The service lets you:

  • Change channels
  • Sort program listings
  • Search the listings
  • Save searches
  • Schedule recordings
  • Link to content-related sites

Other Features

The software also makes it easy to communicate with other viewers over the Web. You can:

  • Select a default chat location
  • Select default instant messaging services
  • Easily access chat and instant messaging

A typical screen shot when using the accessDTV board
A typical screen shot when using the accessDTV board

In the screen shot below, you can see four features provided by the accessDTV software.

Clockwise from upper right:

  • DTV program in a window - The window can also be displayed full-screen or minimized.
  • Personal Program Guide showing you all available programming in your area
  • Regular Web site in a browser - You can run any applications you like while accessDTV is on the screen.
  • accessDTV Virtual Remote Control that lets you select channels, set the volume, change modes, record, pause, fast-forward and rewind

Installing the accessDTV card and software takes 10 to 15 minutes. You can install it in any machine that has a Pentium II processor running at 400 megahertz (MHz) or better as long as the machine has a free PCI slot -- see the bottom of this page for details on the minimum system requirements.

Here is a brief description of the installation process:

  1. Shut down your computer.
  2. Unplug the computer from the power source, and unplug the keyboard, mouse, monitor, speakers, etc. from the back of the computer.
  3. Remove the computer's cover.
  4. Install the accessDTV card in an empty PCI slot.
  1. Replace the cover and plug everything back in.
  2. Attach the supplied cable between the accessDTV card and your video card.
  3. Connect a DTV antenna to the accessDTV card.
  4. Insert the CD in your CD drive and install accessDTV software.
  5. Reboot your machine.
  6. Run the newly installed software.
  7. Tune in a channel and enjoy the broadcast.

You will be able to watch DTV programs in a window or full screen on your computer monitor. If you additionally connect an HDTV display and home-theater sound system to the accessDTV card, you can use your computer as the display's HDTV receiver and save the cost of purchasing an external receiver for the display.

Things to Know Before Installing

You should know about the accessDTV product specifications and minimum system requirements before installing it on your computer.

Product Specifications

  • PCI Bus Mastering DTV Video/Audio Card - accessDTV products sold in North America are compatible with all 18 ATSC digital formats and NTSC video/audio format.
  • ATSC/NTSC TV tuner
  • 125-channel, cable-ready analog TV tuner
  • 69-channel DTV tuner
  • Digital and analog antenna inputs
  • Cable/satellite coax
  • DTV outputs
  • AC/3 surround sound audio
  • DTV video-loopback cable to graphics board
  • Internal stereo audio via PCI bus to compatible sound card

Minimum System Requirements

To operate accessDTV, you will need the following:

  • Pentium II CPU 400 MHz or faster
  • Windows 98SE, 2000 or ME
  • 64 MB RAM for Windows 98SE and ME
  • 128 MB RAM for Windows 2000
  • Open, full-length PCI slot
  • DirectX-compatible sound & graphics card
  • 50 MB of disk space for software installation
  • 4.5 GB recommended per half hour of program content for PVCR functions
  • CD-ROM drive
  • Mouse

For more information on accessDTV and related topics, check out the links on the next page.

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