Question - PCI logic. (PC - not too obscure knowledge)

Hello fine people.

I have recently aquired a TV card. Strangely - to hear the sound I have to plug a cable from the line out of the TV card to the line-in of the sound card.

My question is - why can’t the TV card use the sound card directly? (it is in the same PC afterall) It seems strange that something that is part of the same system as something else needs to ‘leave’ the ‘system’ in order to connect to the “something else”

The TV card can use the graphics card internally/directly. Why not the sound card?


There’s a rather schocking lack of detail provided here, but in any case you’re much better off not carrying the audio signal on the PCI bus. Your hard drives have to use this bus as well, and there’s no point having your hard drives or your audio run slow whenever you do a file search while watching TV.

The TV card doesn’t really “use” the graphics card. Rather, it sends a block of memory to overlay part of your video memory 60 (or 50 for PAL systems) times a second. This is accomplished by rapid copying of one chunk of memory to another. Your sound could not operate along similar lines because sound sampled only 60 times a second would sound awful. You need a sampling rate of at least 60 thousand times a second before you start getting decent quality. It’s much easier to send this as an analog signal through the cables than to try to convert it to digital, send it through the bus, then back to analog.

The TV card might have a place for an internal cable (consisting of red, white and black wires and similar to the cables your CD drive uses) that can be connected to a free input on the sound card. This, at least, will eliminate the need for an exterior cable.

Your CD-ROM also has this type of audio connection only it’s inside the computer. There is a wire, not the ribbon cable, that goes from the CD-ROM drive to the motherboard.

I have a video card and it too has a cord from TV card sound out to audio in.

These are analog signals, not digital.

It seems like you were able to answer the question thoroughly despite the “shocking lack of detail”

I believe any extra detail would have been irrelevant.

Yes, but had you included the models of your TV card and sound card, I would have looked for the manuals on the 'net and described in detail how to connect to two internally, if possible.

Ok Bryan

My TV card is a hauppage WinTV (not sure which model. I think it’s the most basic kind) It has no internal connectors that would allow for connection to the sound card that way.

My sound card is a SoundBlaster live.

This is not a problem as such, I was just curious about why there needs to be a wire between the soundcard and TV card.

It is a bit of an inconvenience though as it allows me only to have mono sound.

Sounds like you need a stereo cable. I believe the SB Live can handle a stereo input.

By design - the TV card will only give out mono sound.

(I would be very surprised and disappointed if the SB Live didn’t handle stereo input)

I think it comes down to that there’s a standard way to interface with video cards (overlay the video memory) and there’s no standard way to interface with audio cards (there is no shared audio memory). So the easiest general solution is an analog plug.

Hauppage does make a TV tuner that doesn’t need that manual plug. The WinTV USB connects via USB and can send the audio over the same bus as well.

The ATI All-In-Wonder series cards connect to the sound card the same way, line out from TV card to line in of sound card.

Seems a rather crappy way to go about it to me. Most sound cards now a days have a spare analog connecter internally, in addition to the one from your CDROM. Seems simple to have a connector on the TV card to make use of it.