How HiFi is XBMC for Xbox audio-output?
#1
Question 
I have always thought that XBMC playing a CD or a wav-file will produce the exact same result as a 5000dollar cd-player when using the digital output on both machines. Is this true?

It's digital all the way, so that would mean that there is only one way of making the output-signal, the right way! or is it??
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#2
only signal processing we do is to upsample it from 44.1kHz to 48Khz.
Upsampling is never without quality losses, so I'd say a player that doesn't need this (most standalone cd players probably) has an advantage right there.
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#3
OK, so what are the advantages of upsampling? Can we just disable it?
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#4
pike Wrote:only signal processing we do is to upsample it from 44.1kHz to 48Khz.

Is this the main reason why DTS-CD (ie DTS 44.1) is not supported?

Cheers Nick
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#5
advantages: we can actually output the audio. the xbox hardware only supports 48khz
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#6
OK, that is a big advantage!

How much of a quality loss is this? Feels like it should not effect the signal since 44.1k < 48k. Isn't it just as simple as adding nothing for frequencies higher than 44.1kHz?

(As you probably know by now, i'm not that well educated in this subject...)
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#7
problem is aliasing during the signal reconstruction / upsampling.

signals might 'fold' into other frequencies, appearing to have lower frequency than they really have (due to our limited grid resolution). this shows up as 'hissing' sounds in the resampled signal. i tried to illustrate what happens here;
aliasing illustration
we only see the signal at the red dots. since we can only observe at this resolution, we cannot tell if we have the slow black signal or the fast blue one.

that only applies if you do stuff the naive way though. we use ssrc which is a high quality resampler which employs an antialiasing procedure which guarantees that this wont happen. so in practice; the only impact is on the cpu (and any slight errors added by our finite precision arithmetics - i promise these are NOT audible)
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#8
i use a external hifi DAC so i got better sounding xbox Smile
but xbox lack of deep bas dont no why..
much more bas with a dvdplayer or cd..

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#9
It doesn't make any sense that xbox digital output should have less bass than other products digital outputs.
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
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#10
Mackan2 Wrote:OK, that is a big advantage!

How much of a quality loss is this? Feels like it should not effect the signal since 44.1k < 48k. Isn't it just as simple as adding nothing for frequencies higher than 44.1kHz?

(As you probably know by now, i'm not that well educated in this subject...)

48K is the samples per second. You are confusing an analog measurement and digital one.

44.1K is an odd-ball sampling rate that Cd’s use. Things would be different if a certain surfing competition had gone differently.
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#11
Damn, you guys know a lot of stuff!

I’ve been converting my Cd’s to 48K MP3’s. Am I wasting my time? I figured that Lame could do a better job up sampling than an on-the-fly- conversion.
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#12
why would you do that ? you gain 0 quality by doing it, you cant gain something that isn't there
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.


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#13
The DAC might be screwing up the bass. I find the base thru xbmc to be quite good although I dont use xbmc for music and leave that to my squeeze boxen whos internal DACs produce great quality audio, much bettr then what the xbox can muster (not xbmc's fault).
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#14
hardly on digital out?
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.
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#15
yeah but if you're using the xbox's DAC you're talking analog out

DAC = Digital to Analog Converter
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.


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