[DECLINED] realtime dc offset removal

Sam_Zen · June 18, 2007, 23:50:55

Quote from: "dBlues"I believe we both are speaking of the same thing

Maybe in some way about the result, as my test shows here, but as Jojo says, shifting up/down doesn't affect the signal.
Why do you think wav-editors all have a special tool for this, while it could be done with some highpass filter ?
In Cool the DC offset tool isn't even in the filter-category, but in the amplify section.

Anyway. On "a" a piece of 0.00001 Hz plus a piece of 10 kHz, with an artificial dc-offset of 15 %.
Then I did a HPF with 1 kHz, and the result is "b". I must admit that I didn't expect the 10 kHz to lower down too, so you got a point there.
Of course the 0.00001 became zero level, because it's silence then.

But I still consider this offset correction as a side-effect of the filter algoritm.

dBlues · June 19, 2007, 16:48:08

The high-pass method is more effective than simply subtracting the dc-offset because this strips the harmful low-frequency waves completely. Merely "decreasing" the zero-level of the wave will keep those waves there. Of course, you can use a 20Hz hp-filter if you feel those frequencies are important in you music (you can only reach 20-50Hz on a subwoofer usually).

Saga Musix · June 19, 2007, 17:32:21

Quote from: "dBlues"strips the harmful low-frequency waves completely

stripping frequencies is just another step in music production... IMHO you should never do two things in one step when you edit audio.

dBlues · June 19, 2007, 18:28:40

Ok, if you have monster offset that is the same throughout the track, by all means use subtraction. Otherwise you will just move the offset around, not causing any improvement. Lets say you have a vsti that causes the offset (or a sample), and you only play it in one part of the song. Now if you would change offset based on this single instrument, you would mess up the offset elsewhere.

dBlues · June 19, 2007, 18:42:44

As for the original topic of phase shifting, that has nothing to do with DC-offset and as mentioned before, is probably a property of cheapo VST-effects(until proven otherwise) and therefore is not a bug at all.

Saga Musix · June 19, 2007, 19:50:33

Quote from: "dBlues"As for the original topic of phase shifting, that has nothing to do with DC-offset and as mentioned before, is probably a property of cheapo VST-effects(until proven otherwise) and therefore is not a bug at all.

lol, i gave up to count how many people misunderstood the problem

BSV corrected himself, he meant the DC offset indeed...

Sam_Zen · June 19, 2007, 22:45:01

I give up too. Decreasing a zero is beyond my imagination

LPChip · June 20, 2007, 07:35:15

Quote from: "Sam_Zen"I give up too. Decreasing a zero is beyond my imagination

Decrease the fontsize

bvanoudtshoorn · June 20, 2007, 10:39:39

Just an idea... Maybe it would be useful to check the offset produced by the "export" feature in mpt against the offset produced using a loopback on a soundcard.

BooT-SectoR-ViruZ · June 20, 2007, 11:06:21

news from the front:
rendered a new track with .48 yesterday that uses a hell lot of vst & vsti
(including the cheap ones i use a lot) and didn't have an insance offset.

only thing i changed while switching versions is that i now try to use xmms
resampling instead of polyphase and i also saved to 24bit wav instead of 16

so maybe that'll also solve my problem with that other track of mine...

testing results to follow in the evening although i'm short of time

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P.S.:
ok, changing bitrate and resampling for export to wav doesn't have any effect on this...
hope i'll find some time for testing again with just plain data at the weekend...