Capture Cards: Smart Or Dumb?
Building A PC-Based Personal Digital Entertainment Centre
A project diary describing the process of building a PC-based home entertainment center based on regular off-the-shelf computer components and software.

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Which Option: Smart or Dumb?
The two type of tuner/capture cards reviewed in this project are representative of "dumb" (the PCTV) and "smart" (the PVR-250).

Note that in this context, "dumb" simply refers to the fact that the PCTV card has no onboard processor and relies on the host PC's CPU to do all the hard work associated with video compression.

So what are the pro's and con's of smart versus dumb when you're choosing a tuner/capture card?

The Dumb Card Option
It may come as a surprise to learn that a dumb card has several very real advantages over their smarter relatives.

Because a dumb card leaves all the processing up to your computer's own CPU, the result can be a far more flexible package.

For example, the PCTV card can, when used with the right software, allow you to decode and watch UHF pay-TV broadcasts such as those transmitted by NZ's Sky TV.

Dumb cards can also capture video in raw, uncompressed format which allows you to perform far more accurate editing and use non-realtime encoding to produce the very highest quality MPEG files. You can also encode into other formats such as DivX, AVI, or a streaming format such as WMF or RealVideo.

If you want to record TV programs and archive them with the very best quality in VCD or SVCD formats then using a dumb card to capture in raw format then edit and compress with a non-realtime MPEG encoder is the only way to go.

Most dumb cards are based on the BT8x8 chipset which also means that you'll likely find plenty of compatible 3rd-part applications. This is particularly important when you look at the decidedly poor quality software that tends to be supplied by the card manufacturers.

Working against the dumb card option is the fact that they are totally reliant on the PC's own processor to perform all the encoding work.

If you have an aging PC with a processor slower than about 1GHz then you're not going to be able to do any realtime MPEG encoding and you may also find that even capturing raw, uncompressed video is impossible at higher (SVCD/DVD) resolutions.

You'll also find that even with a top-end PC, you can't easily record video material and encode in realtime while doing anything else. If you try to perform any degree of multi-tasking you will find the system rather unresponsive and probably end up with a recording that is jerky with sound that doesn't stay in sync with the picture.

If you're planning on using the card as a dedicated PVR as in this Tivo-like project then this probably isn't a problem. However, if you were hoping to be able to record video while also typing up a letter or surfing the web then you might be better to look at the smart capture card option...

The Smart Card Option
So the smart tuner/capture card with its onboard processor must be the perfect solution right?


However, let's look at the pro's of these cards first...

The dedicated onboard processor means that you can capture and encode video in realtime at virtually any resolution and bitrate, regardless of the power of your PC's processor.

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If you've got an older PC and want to do some video capture/recording, or if you want to be able to use your PC for other tasks while capturing video then a smart card is almost certainly going to be your best option.

The realtime MPEG encoding of a smart capture card is almost certainly going to produce better quality than that produced by a dumb card and certainly the Hauppauge PVR-250 creates much better VCD and SVCD files than the Pinnacle PCTV.

But then there are the downsides of a smart tuner/capture card...

First up, you have no access to the raw, uncompressed video that is so handy for a myriad of applications. This means that all you'll get from these cards is MPEG data.

If you want to create streaming content for the Net in WMF, Quicktime or RealVideo format then things become a whole lot more complex and you will end up having to "transcode" (convert from one compression format to another) from MPEG to the required format. Unfortunately, since MPEG and all other streaming formats are lossy, transcoding usually results in a marked reduction in the quality of a recorded video file.

Transcoding is also a rather slow process in many cases.

Another downside of MPEG files is that they are much more difficult than other formats to edit accurately. This means that when you edit out the ads in a recording, the cuts may not take place exactly where you thought -- sometimes producing an annoying few frames of an ad you thought you'd chopped out still being included.

You can also forget using a smart card for decoding your favorite UHF pay-TV channels. Since MPEG is a lossy-format, much of the information needed to establish a good decoding lock is already lost by the time the MPEG stream is spat out by the card. This sort of application really requires access to the raw video

You'll also find that there's far less third-party software available for smart cards such as the PVR-250. That's a bit of a shame, since the software that comes bundled with these cards is very "second rate" and it would be great to find something better.

Here's a table comparing the dumb and smart options to make it easier for you to decide which is best for your intended application:

FeatureDumb cardSmart card
Needs grunty CPUyesno
Offers Raw videoyesno
Allows multi-taskingnoyes
Decode Pay-TVyesno
Realtime MPEG recordingpoorgood
3rd-party softwarelotslittle/none
Linux compatibilitygoodpoor (at present)
Windows XP compatibility variablegood

One thing I've discovered while researching this project is that there is no "perfect" solution to the demands of a Tivo-like PVR unit, there will always be a degree of compromise required.

However, for the purposes of this project, either video card will work perfectly well in the role of a dedicated unit and it's up to you to decide what other benefits you're looking for in a card.

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Published and © 2002 by Bruce Simpson and Aardvark Net Publishing. All rights reserved