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Old 13th March 2015, 06:41 AM   #371
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Quote:
Originally Posted by jaffar View Post
Paul,
i think it is reasonable to make a minimum/intermediate-phase version with (almost) no pre-ringing, similar to Ayre's 'MP Listen'.
Would be a worthy addition to our filter collection.

Thanks!
I'll need to have a play in rePhase, as I haven't found a way to do minimum/intermediate filters with Octave's filter tools. There is a function in Matlab that does this but it hasn't been ported as far as I can tell.

Superdad mentioned that John S had a script that he used to create FIR filters from Sox. So clearly it is possible to do, but I'd have to try to work out how could be done, and that takes time...
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Old 13th March 2015, 07:08 AM   #372
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Default More CRaP™

I might have to drop this CRaP™ seeing we already have Schitt doing scat routines...

Anyhow, one more dose to keep things "regular"...

This is loosely modelled on the Dac Magic Linear Phase setting.
The original is -0.1dB @ 20kHz, -10dB at 22kHz, and hits -140dB at some unspecified point - seems to be 23-24Khz.

Obviously this has to be called...
TotalCRaP™'s CRaP™Magic - linear phase (v1)
Both 44.1kHz and 48kHz use the same coefficients.
The 44.1kHz version is
-0.2dB @ 20kHz
-8dB @ 22kHz
-150dB @ 26kHz
and 496 taps.

FIR2 filters have been updated so that they are closer to flat between 20-30kHz. This version is something like -0.04dB @ 30kHz.

That should help fill in time until the toothfairy drops off a MSB Platinum VI for everyone...
Attached Files
File Type: zip CRaPMagic_LP.skr.zip (3.7 KB, 92 views)
File Type: txt CRaPMagic_LP.txt (36.4 KB, 68 views)
File Type: pdf CRaPMagic_LP_v1_imp.pdf (45.5 KB, 76 views)
File Type: pdf CRaPMagicLP_v1_FR.pdf (152.3 KB, 86 views)

Last edited by spzzzzkt; 13th March 2015 at 07:14 AM.
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Old 13th March 2015, 07:39 AM   #373
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Great work. Will be some filter testing during the weekend!
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Old 13th March 2015, 08:36 AM   #374
Nikitas is offline Nikitas  United Kingdom
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Are you guys following the development of mike moffat's dac over at head-fi? He talks about a filter that deals with effects not only in frequency but also in time domain. Maybe we could try something similar?
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Old 13th March 2015, 09:16 AM   #375
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Default Pull up your SoX...

No magic or special scripts required, just RTFM...

So it took all of about 30 minutes of "suck it and see" to get 99% of the way...

The sneaky trick is the --plot option. What this does with selected SoX effects is to generate a command file which allows you to plot the transfer curve of the effect in Matlab or Octave.

When I first checked using the manual example the results weren't particularly promising - the resulting file contained a couple of equations of the transfer function and plotting commands.

Next attempt using the rate option that John S discusses in posts linked earlier in the thread was a waste of time. It basically doesn't work with --plot option, so no go.

Having a look through the effects listing I noticed that the "sinc" option used the same switches as "rate" but supported --plot. Now we are getting somewhere....

So after a quick peek at the manual page...

Code:
sox --plot octave /path/to/input.wav /path/to/output.wav sinc -20k -I -n 1016 > plot.plt
Holy CRaP™!! the output plot file contained 1016 filter coefficients!

The sampling rate is based on the input.wav, so you need short (1 second is enough) files with 358.2k and 384k sampling rates for FIR1.

From the SoX "rate" documentation...
Quote:
Minimum, intermediate, or linear phase response is selected using the −M, −I, or −L option; a custom phase response can be created with the −p option. Note that phase responses between ‘linear’ and ‘maximum’ (greater than 50) are rarely useful.
I'm excited.
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Old 13th March 2015, 09:30 AM   #376
lcp is offline lcp  Hong Kong
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I have downloaded totalCRaP_rev2 for test. This is the first time to "roll" filter. Everything seems fine. Thanks effort your guys here.
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Old 13th March 2015, 09:32 AM   #377
Stixx is offline Stixx  Germany
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You are really beating the CRaP out of it...
Keep going !
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Old 13th March 2015, 09:51 AM   #378
nusa is offline nusa  Italy
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Quote:
Originally Posted by spzzzzkt View Post
I'm excited.
Just when I was about to comment very positively on your revised CRaP, you are already at your drawing board with more! Great times ahead, many thanks!
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Old 13th March 2015, 01:47 PM   #379
zfe is offline zfe
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In my opinion the passband for the higher sampling rate (88,96 and up) FIR1 filters should also only be something up to 20kHz while the stopband can be at higher frequencies than for the 44/48 case. At least I would wish such a filter set as option.
I think the main benefit of the higher sampling rates is that it makes live easier for building nice filters (as well for recording as for playback). All of my high sample rate recordings, I have looked at, have no content above -90dB from 18kHz, or at most 22kHz, on upwards.
... unless they are (or seem to be) converted DSD recordings which have a (noise) signal reaching higher levels above 35kHz again:
Spectrum.jpg

Last edited by zfe; 13th March 2015 at 02:02 PM.
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Old 13th March 2015, 02:56 PM   #380
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I'm really enjoying CrapMagic! Great work!

Quote:
Originally Posted by spzzzzkt View Post
I might have to drop this CRaP™ seeing we already have Schitt doing scat routines...

Anyhow, one more dose to keep things "regular"...

This is loosely modelled on the Dac Magic Linear Phase setting.
The original is -0.1dB @ 20kHz, -10dB at 22kHz, and hits -140dB at some unspecified point - seems to be 23-24Khz.

Obviously this has to be called...
TotalCRaP™'s CRaP™Magic - linear phase (v1)
Both 44.1kHz and 48kHz use the same coefficients.
The 44.1kHz version is
-0.2dB @ 20kHz
-8dB @ 22kHz
-150dB @ 26kHz
and 496 taps.

FIR2 filters have been updated so that they are closer to flat between 20-30kHz. This version is something like -0.04dB @ 30kHz.

That should help fill in time until the toothfairy drops off a MSB Platinum VI for everyone...
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