[DECLINED] realtime dc offset removal

BooT-SectoR-ViruZ · May 04, 2007, 07:46:54

i don't think this will be possible at all, but it would imho be a freaking nice feature.

ofcause you can kill the dc delay / phase shifting with some wave-editor after rendering your file to .wav, but that will be of no use when performing live with ompt.
(began to think about this problem after i listened to the recording of my gig in leipzig on april 20th... some instruments with stereo vst effects just couldn't be heard...)

i also had another feature request in mind 5 minutes ago, but unfortunately i forgot

:?

LPChip · May 04, 2007, 07:50:30

When I read your post, I see you being enthousiastic about your idea, but not really what your idea will do, and how it will work.

Can you elaborate this a bit more?

BooT-SectoR-ViruZ · May 04, 2007, 10:54:22

unfortunately i'm not a big specialist with the technical stuff,
so please tell me what it will do that's not to wish for....

i'd just like to have "remove dc delay" that i know from wavelab as an optional realtime process in ompt.

thx

LPChip · May 04, 2007, 11:00:22

Thanks for the clearification. This makes more sense.

Sam_Zen · May 04, 2007, 22:17:28

I'm a bit of the technical stuff, but I'm not capable to imagine what you mean by "dc delay"..
So I like to know about the result of killing it with a wave-editor, as you mentioned. What exactly is the result of that correction ?
With which function ?

Snu · May 05, 2007, 06:32:28

i have no idea what dc delay is either, and im very much into the technical stuff :p
i know that phase shifting would be a very small delay in one channel, but modplug's output shouldnt have any problem with this, the channels should be perfectly synched... and if they arent, this should be in bug reports!

Saga Musix · May 05, 2007, 11:11:53

In wavelab, there is an option called "Remove DC Offset" (we discussed that before in one of cubaxd's threads), but I don't know about a DC delay, coz DC is something on the y-axis, but phase shifting is something on the y-axis of a sample.

Sam_Zen · May 05, 2007, 22:36:20

I thought about the offset too, but, as Jojo says, this is an y-axis, so no time or delay involved. Phase shifting of a wave could be seen as a shift in time, but I doubt if this is theoretically correct.

Quote from: "BooT-SectoR-ViruZ"some instruments with stereo vst effects just couldn't be heard

This could be the case, if one of the channels of the stereo has a phase-inverted (180°) version of some common signal.
Not a matter of some delay of course.

Saga Musix · May 06, 2007, 09:59:45

jep. if some waveform can't be heared, it's got an inverted channel. that means:

Code Select


Left Channel
\_/¯\
Right Channel
/¯\_/

You see, if you sum them together, they would always be zero.

BooT-SectoR-ViruZ · May 08, 2007, 07:43:37

ofcause i meant offset...

(this is the problem when you write requests at work...)

now let's see what wikipedia has on that one:

Quote from: "en.wikipedia.org"
DC offset is an offsetting of a signal from zero. The term originated in electronics, where it refers to a direct current voltage, but the concept has been extended to any representation of a waveform. DC offset is the mean amplitude of the waveform; if the mean amplitude is zero, there is no DC offset.

DC offset is usually undesirable. For example, in audio processing, a sound that has DC offset will not be at its loudest possible volume when normalized (because the offset consumes headroom), and this problem can possibly extend to the mix as a whole, since a sound with DC offset and a sound without DC offset will have DC offset when mixed. It may also cause other artifacts depending on what is being done with the signal.

sounds pretty much like my problem..

Snu · May 08, 2007, 17:27:01

ok, i get it now, still sounds like it should be in the bug forum rather than feature requests tho... unless its caused by vsts?
does plain mpt output have that problem, or just some vsts?
regardless, maybe there is a vst plugin that can do this

Sam_Zen · May 08, 2007, 23:13:41

If it's about a sample with DC offset, then it's not a bug of MPT, because it's a property of the sample. To correct this to zero could be seen as a request for adding this tool to the sample editor of MPT. But this correction should have been done with a wav-editor before importing into MPT.
Missing instruments is something else, so it's a good suggestion to test this with a plain MPT output.

BooT-SectoR-ViruZ · May 09, 2007, 08:25:05

Quote from: "Sam_Zen"If it's about a sample with DC offset, then it's not a bug of MPT, because it's a property of the sample. To correct this to zero could be seen as a request for adding this tool to the sample editor of MPT. But this correction should have been done with a wav-editor before importing into MPT.
Missing instruments is something else, so it's a good suggestion to test this with a plain MPT output.

i assume it's a problem with cheap vst effects, so no bug.
but i'm also going to do some testing with plain mpt output,
because when i was rendering a track yesterday (v .46)
i got ~6% offset, which is a freaking lot... (normally 0% - 1%)

Quote from: "Snu"maybe there is a vst plugin that can do this

according to some article on kvraudio there are some,
but having it build in would be better for mix and performance i guess

pelya · May 09, 2007, 11:09:57

Maybe write VST plugin that removes DC offset? And chain it with those VSTs that adds it :lol: .

Sam_Zen · May 09, 2007, 23:47:36

Quote from: "BooT-SectoR-ViruZ"i got ~6% offset, which is a freaking lot... (normally 0% - 1%)

6 % is awful. How did you analyze this ?
Imo even 1 % is unacceptable by the way. A good formula shouldn't change the DC-offset of the output.

The DC-level at the output can be caused by any single audio-source within the mix. Having the offset at zero
means that the total energy of the negative part is in balance with the positive part of the wave.
So any element which doesn't have this, could disturb the overall balance at the output.
Devices which are known for delivering signals with a wrong DC-level are microphones and pickup elements.