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Sample rate conversion
MannyCalavera
post Apr 11 2011, 18:50
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Hello everyone.

I have a question regarding sample rate conversion algorightms.
I don't know how they work, but I guess you guys are more familiar with this biggrin.gif

Let's say I have a 48 kHz wave file that I want to use in something I have to mix
with some 96 kHz material at certain places. This requires the 48 kHz file be resampled
and in the end back to 48.

So in short: does resampling 48 --> 96 --> 48 change the original or can the original
be restored 100% ?

I'm using Wavelab for this.
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Wombat
post Apr 14 2011, 01:11
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QUOTE (saratoga @ Apr 14 2011, 01:03) *
Although you can never make a perfect sinc filter, its possible to build ones very very close to perfect, such that any difference is below quantization noise except for a tiny region right around the Nyquist limit, which of course won't include audio anyway because of the anti-alias filter on the original recording ADC.


I am pretty sure we can get close but from reading some earlier posts in this thread it is suggested that 2x upsampling will leave the source material intact which it is not. One can argue about such ultra-close filters have huge amounts of pre-ringing btw.
It is not a lossless operation.
I see it in the context of some audiophile claims about upsampling 2x from 44.1 to 88.2 for example sounds better as to 96kHz cause of only applying zeros on every second bit, but it isnīt.

This post has been edited by Wombat: Apr 14 2011, 01:15
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saratoga
post Apr 14 2011, 01:17
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QUOTE (Wombat @ Apr 13 2011, 20:11) *
QUOTE (saratoga @ Apr 14 2011, 01:03) *
Although you can never make a perfect sinc filter, its possible to build ones very very close to perfect, such that any difference is below quantization noise except for a tiny region right around the Nyquist limit, which of course won't include audio anyway because of the anti-alias filter on the original recording ADC.


I am pretty sure we can get close but from reading some earlier posts in this thread it is suggested that 2x upsampling will leave the source material intact which it is not.


Obviously if the filter does not have unity transmittance at every frequency, then at least some samples cannot be the same . . .
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Posts in this topic
- MannyCalavera   Sample rate conversion   Apr 11 2011, 18:50
- - saratoga   QUOTE (MannyCalavera @ Apr 11 2011, 13:50...   Apr 11 2011, 18:58
- - Arnold B. Krueger   QUOTE (MannyCalavera @ Apr 11 2011, 13:50...   Apr 12 2011, 14:29
- - Axon   If you are just mixing, then you ought to be able ...   Apr 12 2011, 20:09
|- - 2Bdecided   QUOTE (Axon @ Apr 12 2011, 20:09) If the ...   Apr 13 2011, 15:21
|- - Axon   QUOTE (2Bdecided @ Apr 13 2011, 09:21) Th...   Apr 13 2011, 22:43
|- - Canar   QUOTE (Axon @ Apr 13 2011, 14:43) I think...   Apr 14 2011, 00:03
|- - Axon   QUOTE (Canar @ Apr 13 2011, 18:03) QUOTE ...   Apr 14 2011, 03:26
- - Wombat   QUOTE (2Bdecided @ Apr 13 2011, 15:21) Yo...   Apr 13 2011, 16:05
|- - bandpass   Given 10 seconds of 440Hz tone and upsampling from...   Apr 13 2011, 20:25
|- - Wombat   QUOTE (bandpass @ Apr 13 2011, 20:25) Giv...   Apr 13 2011, 20:47
|- - bandpass   QUOTE This must be lowpassed already even if i don...   Apr 13 2011, 21:19
- - Wombat   I admit i have no clue about some things you talk ...   Apr 14 2011, 00:44
|- - Canar   QUOTE (Wombat @ Apr 13 2011, 16:44) I adm...   Apr 14 2011, 00:52
||- - Wombat   QUOTE (Canar @ Apr 14 2011, 00:52) Sample...   Apr 14 2011, 00:58
||- - Canar   QUOTE (Wombat @ Apr 13 2011, 16:58) Exact...   Apr 14 2011, 01:03
|- - saratoga   QUOTE (Wombat @ Apr 13 2011, 19:44) I adm...   Apr 14 2011, 01:03
- - Wombat   QUOTE (saratoga @ Apr 14 2011, 01:03) Alt...   Apr 14 2011, 01:11
|- - saratoga   QUOTE (Wombat @ Apr 13 2011, 20:11) QUOTE...   Apr 14 2011, 01:17
|- - bandpass   QUOTE (saratoga @ Apr 14 2011, 01:17) Obv...   Apr 14 2011, 07:30
|- - Axon   QUOTE (bandpass @ Apr 14 2011, 01:30) QUO...   Apr 14 2011, 19:38
|- - bandpass   QUOTE (Axon @ Apr 14 2011, 19:38) Strictl...   Apr 14 2011, 20:24
- - Wombat   QUOTE (bandpass @ Apr 14 2011, 20:24) aft...   Apr 14 2011, 20:46
|- - bandpass   QUOTE (Wombat @ Apr 14 2011, 20:46) I sti...   Apr 14 2011, 22:16
|- - Alexey Lukin   QUOTE (bandpass @ Apr 14 2011, 17:16) Bec...   Apr 14 2011, 22:26
|- - Wombat   QUOTE (bandpass @ Apr 14 2011, 22:16) Usi...   Apr 14 2011, 22:27
|- - bandpass   QUOTE (Alexey Lukin @ Apr 14 2011, 22:26)...   Apr 15 2011, 07:18
- - Alexey Lukin   48 -> 96 kHz conversion may leave signal sample...   Apr 14 2011, 21:35
- - Wombat   QUOTE (Alexey Lukin @ Apr 14 2011, 21:35)...   Apr 14 2011, 21:49
- - Wombat   I am getting slowly mad in here or lowpass myself ...   Apr 14 2011, 22:49
|- - bandpass   Okay, curiousity got the better of me: in the 48k ...   Apr 15 2011, 10:39
- - Wombat   Many thanks bandpass for your efforts. Very intere...   Apr 15 2011, 16:24
- - Alexey Lukin   I've just verified that SoX never preserves th...   Apr 15 2011, 17:10
- - Wombat   QUOTE (Alexey Lukin @ Apr 15 2011, 17:10)...   Apr 15 2011, 18:11
|- - bandpass   All I have told you is what I have observed throug...   Apr 15 2011, 22:17
- - Alexey Lukin   This is only due to the fact that you used the sin...   Apr 16 2011, 06:27
- - bandpass   QUOTE (Alexey Lukin @ Apr 16 2011, 06:27)...   Apr 16 2011, 08:41
- - Alexey Lukin   Agreed.   Apr 16 2011, 08:45


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