Looking for PulseAudio clarification on performance/decoding/resampling/passthrough

[uomiarz]

I am following threads about pulse audio issues with ubuntu and I have everything running OK now (with one of the latest SVNs and pulse audio support) Thanks to Topfs2 for support and whole XBMC dev team.

Here is the question. It is more about sound processing and less about pulse audio I guess. AFAIK currently pulse audio does'n not support passthrough. My system is plugged with optical cable(S/PDIF) to DD/DTS enabled receiver.
I have all movies/music videos playing DTS and DD fine (DVDs/mkv)

If pulse audio doesn't support passthruogh then it means that PC is decoding the signal and then sends it to receiver ?
If PC is doing the job then it means that it uses some CPU/memory resources needed for video decoding.
Isn't it better to run without pulse audio and let ALSA do passthourgh (i don't know if this is happening currently if pulse audio is killed) and let receiver do decoding?

I am aware of the fact that I probably doesn't understand how that process works. Maybe someone with knowledge can explain a bit. I will greatly appreciated it.

I have lots of DTS wav files that linux XBMC doesn't play at all (noise) while original XBOX do great job (DTS/DD) decoding. I am thinking passthrough is somehow the issue here :)

thx
mike

[mr_raider]

I can't tell you the details of it. What I can tell you is that most modern CPUs won't break a sweat decoding audio. It is far less intensive than HD video decoding for example.

[uomiarz]

That's what I was thinking.
So why people need passthrough then? And why my DTS files will not work with linux XBMC

[topfs2]

Thats exactly why you need passthrough ;) because the OS then doesnt need to be able to decode em. you just pass the data through to the amp and let it decode.

Cheers,
Tobias

[uomiarz]

So it is expected behavior from linux XBMC not to decode DTS wav files?

[BLKMGK]

The receiver does the decoding, software just tosses it out the port...

[uomiarz]

The receiver does the decoding, software just tosses it out the port...

If passthrough is not working then it was my understanding that XBMC decode DD/DTS.