What is HDTV Decoder?

By | May 16, 2011

A key component for great HDTV using a PC tuner is the decoder. Microsoft Media Center video decoder and audio decoder compliant software is used by most HDTV PC tuner applications.

What are decoders and why do you need them? Currently, all HDTV/digital broadcasts are compressed in what is called the MPEG-2 format. That means what you receive via cable, satellite or over the air is not ready for your monitor/HDTV. The signal first needs to be decompressed to the original format and that’s where decoders come in.

HD TV Decoders come in two flavors, hardware and software. A hardware decoder is basically a computer chip whose sole purpose is to decompress MPEG-2 data. All cable and set-top box digital/HDTV tuners use hardware decoding. A software decoder is just a computer application that runs somewhere on your PC (we’ll get to that “where” in a second) and does the same thing as the hardware decoder, decompresses MPEG-2 data.

The advantage to hardware decoding is that it’s very efficient and self-contained. The disadvantage is it can only perform this one task. That means if you want to do different decoding you have to swap out the chip or in this case the set-top box. One satellite provider has found this out the hard way, as they are the process of changing to a more efficient compression routine to get more programs on the same bandwidth. Unfortunately, this will entail scrapping all their current digital tuners equipped with MPEG-2 hardware decoders.HDTV Decoder

BCM970012 PCI-E Tuner with decoder is the best hardware decoder in the PCI Express Mini Card form factor. Enables support for H.264 and VC-1 video playback of local files and streaming 1080p high definition multimedia content. It’s a video/audio mini pcie decoder, it is designed to reduce CPU utilization and allows for full HD real-time decoding support for mobile platform solutions.


The advantage to software decoding is its versatility. Software decoders can easily be changed or modified as they are just applications. The disadvantage is they need to use a processor to run. Since decoding HDTV broadcasts is very high overhead (uses lots of processor), if the decoders relied solely on the PC’s processor they could easily drive even a powerful computer in the dirt. Microsoft realized this, but wanted the flexibility of software decoding for their Media Center application. They came up with a standardized process to off-load much of the decoding chore to the graphics/video card. Their software is called DXVA (Microsoft® DirectX® Video Acceleration).

Most, if not all, software video decoders use or can use DXVA. You’ll need to have DirectX 9.0 loaded on your computer to use DXVA. Luckily, it’s already there if you have any of the Windows XP operating systems.

In an effort to be compatible with Media Center, the most popular Windows compatible HDTV PC tuners use software decoding with the exception of the MyHD card. And, strangely enough, the MyHD is the only tuner that will not run under Media Center (go figure).

There are several software decoders on the market, all tuners that come with their own application software. Tuners without applications do not include decoders with their product. Media Center 2005 does not have its own decoders, so depending on the HDTV Tuner you purchase, you may also need to acquire software decoders.

Other applications may also load decoders on your PC, so to check if you already have appropriate decoders, go here, download, install and run this Microsoft Decoder Check Utility.

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