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Sep 10, 2003, 09:13 AM
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#1 |
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DriverHeaven Newbie
Join Date: Jul 2003
Location: UK
Posts: 18
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Sample depths
When a PCM stream (for example, when I play a CD or an mp3) is sent through the DSP (of an Audigy2 OEM card), is it automatically converted up to 24 bits? If not, how can this be accomplished? I ask because I use the Parametric EQ from the ufx pack quite heavily to increase my low bass at around 12dB/octave so that I get a flat response from my subwoofer (I also remove a pair of room modes with it). Once I get down to about 20Hz I have 15dB of gain - this means that to avoid clipping I've had to set the overall gain to -6dB, and if the sample depth is only 16-bits this digital attenuation could be a real loss of information.
Do I have to choose between a flat response and overall detail (I really hate the boomy 80Hz that I get without EQ) or can I upsample the streams to 24-bits prior to EQing, and hence keep the resolution?  I saw the 16to32 effect in the Passthru category but can't quite figure out what it does. The same goes for a few of the other plugins in kX (call me thick!). Could ambiguous or little-known plugins have a comment added into the microcode briefly explaining their function? TIA |
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Sep 10, 2003, 06:00 PM
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#2 |
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kX Project Lead Programmer and Coordinator
Join Date: Dec 2002
Posts: 2,957
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the 16-bit audio is converted into 32bit internal representation when it gets inside the DSP
it is then processed with mixed 24/32bit accuracy (depending on the effects you are using) the output resolution for audigy2 is 24 bit (that is, the 24 bit DSP data is passed to 24-bit DACs) anyway, there might be better ways of achieving your goals  /E |
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Sep 10, 2003, 06:18 PM
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#3 |
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DriverHeaven Newbie
Join Date: Jul 2003
Location: UK
Posts: 18
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So the precision is fine for what I'm doing, which is nice. Thanks for the clarification.
What are the better ways? Analogue EQs? |
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Sep 10, 2003, 08:38 PM
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#4 |
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d/h member-shmember
Join Date: Dec 2002
Location: from the edge of the deep green sea
Posts: 2,207
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>it is then processed with mixed 24/32bit accuracy
correction: DSP processing itself is done with 32/64bit accuracy |
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Sep 10, 2003, 09:26 PM
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#5 |
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DriverHeaven Newbie
Join Date: Jul 2003
Location: UK
Posts: 18
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Hell, 64 bits? I'm impressed with that. That's some pretty accurate processing.
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Sep 12, 2003, 09:38 AM
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#6 |
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kX Project Lead Programmer and Coordinator
Join Date: Dec 2002
Posts: 2,957
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well, Max, if we wish to be 100% correct, then it is 24(16)/64
(24(16) is external tram resolution, 32 is the DSP GPR resolution and 64 is DSP accumulator resolution) anyway, '32bit processing' seems to be the 'golden mean' /E |
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Sep 12, 2003, 11:30 AM
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#7 |
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d/h member-shmember
Join Date: Dec 2002
Location: from the edge of the deep green sea
Posts: 2,207
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Ok, ok... Let's do not fall into deep discussions here...
If we are speaking about equalizers (as this thread is inventionally of) then their precision is 32/64 (ufx eq and Soeren's filters use accumullator _very_ hardly and do not use TRAM)... Last edited by Max M.; Sep 12, 2003 at 11:54 AM. |
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Sep 12, 2003, 05:18 PM
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#8 |
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kX Project Lead Programmer and Coordinator
Join Date: Dec 2002
Posts: 2,957
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ok
I doubt we could have fallen into a deeper discussion, since all the precision discussion stuff is now present in this thread /E |
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Sep 25, 2003, 03:00 PM
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#9 |
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DriverHeaven Junior Member
Join Date: May 2003
Location: Scotland
Posts: 29
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OK, if we're going to be really picky, the 10k1 (and presumably 10k2) have a 67-bit accumulator in the FX processor and does 32-bit integer/fixed-point processing... from my reading of the EMU FX8010 architecture document
 Matt |
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