A little sleuthing please, experts...

[Sprogget]

I'm back with my sound woes...

I use my system for two things; ppruning & media centre. Ppruning's ok...

It's an asus p5l-vm mobo, 2x500gb hdd's, 2gb ddr ram, an nvidia 8500gt gpu, two Hauppauge tv cards, a nova-t 500 & an hvr 1700.

Now up until 2 weeks ago, on Vista tv pack, I had perfect 5.1 surround sound. Then I started to experience ups & downs in the volume. This was with a Creative xfi extreme audio card, which I didn't much rate anyway. So I changed it for an xfi extreme music. All was well for a while, but now I have lost 5.1 on live tv only I.e. on Video & music, the sound is perfect, but on tv, it only comes out of the front two speakers.

I have tried all new drivers, uninstalled & reinstalled the software, cc cleaned the system, deleted all Creative folders & registry entries prior to reinstallation & as a last resort, rebuilt the system from scratch.

No joy. Then I cleaned out again & installed the extreme audio card. Same result. So now I'm thinking the odds of two cards being faulty across two builds & two os'es (it's 7 rc1 dual boot) are remote. So if I can discount the os & I can discount the cards, could this leave the mobo?

I've flashed the bios & run all manner of diagnostics from memtest to Belarc to asus pc probe & all reports are fine.

I've built systems for years & never had such an intractable problem. I'm sorry for the long post, but I'm running out of ideas & would welcome fresh eyes. Ta.

[green granite]

It seems to me (although it's not my field) that if its works ok on video then the card is ok, so perhaps there is a box to tick in the TV cards set up somewhere? Or a lead not plugged into the right place?

Have you tried asking here?
Hauppauge UK Forum - Powered by vBulletin (http://www.hauppauge.co.uk/board/index.php)

[Sprogget]

The forum is well stalked by me:)

I am thinking that the card is ok, The settings have been shuffled to death, but I am thinking about resetting the cmos and before thst checking there's no loose wires on the mobo.

The tv cards are both just on drivers only rather than software too, but they have been since xp media centre, so across three builds now, I understand that they just pass through the audio signal with no processing & what the soundcard does is called 'upmixing' to split the signal into 4.1, 5.1 or 7.1 as the speakers require.

However, I am still stuffed.:(

[Keygrip]

How do you know for sure that the original broadcast is actually carrying 5.1 sound?

If the problem is "TV only" then I'd be tempted to check, by some other means, that there is a 5,1 signal there.

[Sprogget]

I wondered that Mr. KG, but the two tv cards are to receive two discrete tv sources. Freeview digital & Virgin cable analogue. Again. it's a probability thing that both sources have opted to reduce the audio input simultaneously. I'm sure it's in the box somewhere.

The tv pack add on to media centre allows a user to take mixed digital & analogue sources which is a new thing for media center. We get the red button too:)

[gizmocat]

I know that Virgin are cutting back on their analogue stuff at the moment. More info on here :- Cable Forum (http://www.cableforum.co.uk/)

[Sprogget]

Well a lot of reading & messing about later & I think I have it nailed.

Over the weekend, I decided to do a fresh install of Vista. Since I know that I had 5.1 & now don't, something has intervened to change the audio stream.

Anyway, fresh install gave perfect sound. Add SP1, still perfect sound. Now here's the thing, MS issued an update to media centre called tv pack. Essentially it allows users to mix tv sources whereas Vista & previous versions would allow analogue or dvb but not both. This means in practice that I can hook up freeview and sky together and use HD as required. Tv pack also changed the audio plumbing & it's when I add this that the surround disappears.

However, I have had surround audio with tv pack previously so I still can't say for sure that tvp is the issue, but it is definitely somewhere between tvp & the soundcard. Tv capture cards do not process audio in any way, they merely pass it on to whatever audio device is in the pc. The soundcard splits the signal in to stereo & sends it out in what is effectively a contrived signal. Somewhere in that processing, there is a bug.

So I'm still stuffed, but I more or less know why I'm stuffed.:ugh:

[Sprogget]

Fixed! I'm unstuffed.

I managed to get hold of someone helpful from the programming team for tv pack at Microsoft on another place. It turns out that in the development process, Ms altered the audio codec to sync it with h264 (hi def) video codec. In testing, they found that the new audio codec struggled with higher bit rate audio processing.

So where I had my 24 bit soundcard configured to 24bit output in Windows, I've had to throttle it back to 16 bit to restore the 5.1 audio. In practice, the difference is not apparent to the mk1 ear.

Who knows, someone may come along after me with the same problem & read this & go away happy. It could happen...