[Teeh]

I've been making a list of components to upgrade an existing PC for double duty (not at the same time) as an HTPC. I want to play DVDs and view and record ATSC over the air broadcasts, with full 5.1 surround-sound when available. A major constraint is a limited budget. Thus, I want to be able to use my three existing legacy stereo amplifiers and speakers, and the sound card/software for AC3 decoding.


Most current sound cards have 5.1 (six channel) line level outputs, but it seems that these depend on the soft DVD player software for AC3 decoding as well as for sending the AC3 stream to the sound card's S/PDIF output(s). So far, so good. With my three amps, I should be able to get good 5.0 sound since all speakers are full range and amps have numerous controls. I reckon the setup will work well even with DVD Audio if the soft DVD player supports it.


Now, what happens if one wants to send the AC3 stream from an HDTV tuner card's S/PDIF output to the sound card's S/PDIF input? And the sound card depends on software for AC3 decoding? The soft DVD player software won't decode any AC3 other than that from the DVD, will it? Is software for general AC3 decoding supplied along with sound cards? Or would I need a sound card with hardware AC3 decoding like the CL SB Extigy.


In summary, what sound card software or PC-based hardware are known to provide AC3 decoding for HDTV tuners.

 

[theturtle]

Hey guy, I think you may be confused, the hdtv incoming will be played thru the software on the pc. The pc software should detect the current sound card and direct the sound internally to the sound card. I don't see any need for spdif output on the hd card or spdif input on the sound card. Once the sound stream is directed internally, it'll be up to the drivers to decode the ac3 which if you have software or hardware support for in the card, it should do.


p.s. TO anyone reading, Some radio station i was in a few weeks ago working on a pc, had some single channel ac3 hardware decoder cards, is there such a thing as single channel ac3 cards? :/

 

[Mark Mac]

Teeh


Why not just pass the ac3 from the hdtv card to your sound card and then onto your receiver and let it do the decoding? The Phillips dynamic edge 4.1 will let you do this and it only a $30 card at Bestbuy.

 

[Teeh]

Thanks guys. I think I got it. As you can see, I'm not experienced at all with sound cards, nor HDTV cards. I'm making a shopping list at this point.


The Turtle says that I don't need to do anything but to have the PCI HDTV card and a capable PCI sound card and its software installed. The HDTV card sends all sound including the AC3 stream via PCI to the sound card's software and into the sound card where the sound card sends sounds to one or more of its analog outputs properly decoded according to the source sound. That's great. Thanks.


However, it is not clear in Mark Mac's message as to how the HDTV card's sound is passed to the sound card, via PCI or via external S/PDIF connections. Also, "let it do the decoding" means which, the sound card or the receiver. I hope this refers to the sound card, because each of my three legacy receivers can only accept line level stereo inputs.


I hope these responses are based on actual experience, rather than theory. Again, thanks.

 

[ChrisW6ATV]

Teeh-


Your question is the first one I have seen looking for internal decoding of HDTV Dolby Digital into 5.1 analog outputs. I am not aware that anyone has done that yet, or if it is even possible.

 

[Teeh]

Cris, you may be right. I didn't find any such posts either. I've also asked HDTV PC card and sound card manufacturers and their reps were of little help.


Someone at CL said that I needed to go via external S/PDIF out/in to their Extigy (with its hardware decoding, this seems a winner) or to the Audigy 2's expansion drive (seems to be software decoding?).


I hope someone who has both types of cards will tell me whether they have ever tried such an internal solution, and the results.


Thanks to all who responded.

 

[theturtle]

Any people that know alot about hdtv cards want to explain this to teeh, I apologize teeh i gave you bad information, i didn't read your post right. Will the software for the hdtv tuner use a system's ac3 software decoder and output through the sound cards analogue outputs? Teeh I figure it will, but I dont want to assume anything. Most hdtv tuners have audio outputs but it seems like it should be able to take advantage of your sound card as well. meaning output thru your analogue outputs. This is a good question, as I'll be doing this myself as soon as i buy my hdtv card.

 

[jkaiser]

All the audigy, and probably the Sound Blasters, have AC3 decoding drivers. There is a checkbox that must be unchecked if you want SP/DIF output. I do not think however that it is as good as those found in receivers that have DD decoders.


I have the MyHD card that can send the audio to the sound card via either a cable or as Wave. There seems to be a problem however with sync, with these as there is extra processing that is required by the PCI bus or the cable. The cable is better, but not perfect.