Sound card consideration for HTPC

[asun]

Need guidance from the good folks here. Currently, I have an HTPC based on HP Slimline (nice form factor). I pretty much have everything configured nicely, but suddenly I have this itch to get a real sound card instead of the onboard sound.

The current onboard sound is based on ALC883 chipset and only the S/PDIF out is used to connect to the receiver. I'm thinking of getting one of the CMI8770 based soundcard. My question is, will the improvement be worth it?

Here are my thoughts, correct me if I'm wrong:
1. Movies from DVD are using AC3 or DTS passthrough, so there won't be any improvement.
2. Downloaded movies are usually encoded using mp3. Can the soundcard do hardware DD or DTS encoding on the fly? Currently alsa can do the stereo upmix using a52 but will the soundcard based upconversion be better? Can the soundcards do the hardware encoding in linux? More importantly, will the result be better than the receiver's upconversion (Dolby Pro Logic and what not)?
3. For music (mainly mp3), will there be much improvements vs onboard sound?

[Redeeman]

DD or DTS encoding will remove details you know... its best to play back pcm, or if you really want to do decoding off-computer, send a raw dd/dts stream out if you have one(NOT create one from pcm.)

[Kano]

If you use SPDIF there will be no diff between onboard and dedicated solution.

[asun]

Kano, just to make sure, if an mp3 is decoded and sent out in PCM form through SPDIF, it makes no difference what sound card is used? Does it make any difference what decoder is used? e.g. gstreamer or mpg123?

[deanjo]

Kano, just to make sure, if an mp3 is decoded and sent out in PCM form through SPDIF, it makes no difference what sound card is used? Does it make any difference what decoder is used? e.g. gstreamer or mpg123?

Mp3 decoder can make a small difference (although if your that concerned on sound quality your better off encoding your music to a better codec such as flac). But Kano is correct, if your using spdif there is little to no reason to look at a discreet solution as your receiver is responsible for the final digital to analog conversion.

[Redeeman]

Mp3 decoder can make a small difference (although if your that concerned on sound quality your better off encoding your music to a better codec such as flac). But Kano is correct, if your using spdif there is little to no reason to look at a discreet solution as your receiver is responsible for the final digital to analog conversion.

There is however the matter of how precise the clock on the "soundcard" is... a dedicated soundcard may well have alot less jitter than an onboard solution, and its very few recievers which actually buffer and reclock..

[Kano]

You are the one who would buy a cd cleaner which makes the sound more natural

[Redeeman]

no i am not :P i do however have a fairly complete understanding of how stuff works, and i know that some soundcards, mostly onboard, have a very inaccurate clock..

this is scientifically proven and known stuff :P

[deanjo]

no i am not :P i do however have a fairly complete understanding of how stuff works, and i know that some soundcards, mostly onboard, have a very inaccurate clock..

this is scientifically proven and known stuff :P

True, but his media that is playing is all lossy media as it is. If clock drift was the biggest audio concern then they really wouldn't be playing lossy media in the first place.

[asun]

Redeeman, so how much difference is the clock jitter on regular onboard sound going to affect the final audio quality (vs a good soundcard)? I'd guess jitter is probably bad for VoIP, but how about pre-recorded stuff?