[DECLINED] realtime dc offset removal

[BooT-SectoR-ViruZ]

i got ~6% offset, which is a freaking lot... (normally 0% - 1%)

6 % is awful. How did you analyze this ?

rendered my song to .wav and let wavelab 5 check on that....

funny thing is that before i remove the offset in wavelab, silent parts of the song don't show any waveform (as it's supposed to be) and after removing the offset there's a waveform without any noticeable sound.. haha

[BooT-SectoR-ViruZ]

we seem to have a bug here.... (at least in v45 and v46, with which i tested)

i tested 20 different modules and all rendered wav-files had more or less dc offset.
(no vst stuff involved)

even when you create a stereo-wav-file from just a looped mono-sample
(also with removing dc offset from that sample in wavelab before)

my settings:
mixing 44.1khz
stereo 16bit
stereo separation 100%
pre-amp ~40%
polyphase resampling
no eq, no agc, no bass expansion....

[LPChip]

Can you see if anything in the player settings is affecting this? Like EQ, Surround option, etc?

I know that rendering to wave will use these settings. Hench why you can press a button on the wav export options.

[Saga Musix]

6 % is awful. How did you analyze this ?

i guess he used wavelab if you use the "Remove DC" option it will show you the current offset.

[Sam_Zen]

I tested XM and IT with .45 and .46 under the same circumstances, but I can't reproduce this problem so far.

[BooT-SectoR-ViruZ]

Can you see if anything in the player settings is affecting this? Like EQ, Surround option, etc?

I know that rendering to wave will use these settings. Hench why you can press a button on the wav export options.

i'll check on that during the weekend...

@sam_zen:
did you normalize/amplify your output wav-file to a normal level?

[Sam_Zen]

I never use normalize in the wav export.

[BooT-SectoR-ViruZ]

I never use normalize in the wav export.

me neither... i meant in the wav editor that you're checking dc offset with

[Saga Musix]

as far as i can see, the normalize feature is not there in openMPT anymore. which is a bad choice imho. i kinda liked it.

[BooT-SectoR-ViruZ]

as far as i can see, the normalize feature is not there in openMPT anymore. which is a bad choice imho. i kinda liked it.

please keep on-topic

[Sam_Zen]

i meant in the wav editor that you're checking dc offset with

I see. As a test I exported a module to wav, then imported it in the wav editor, as is, and checked.

There are ways to localize this problem better, I think.

First, a piece of silence in the track can indicate something, because this should be just a line on zero level.
This could be tested, by adding an empty pattern with e.g. some 32 lines before the song starts.
This silence will be exported too. Then a global DC offset would look like this



Another option is to check the behaviour of the seperate channels if exported as solo. This can be done by enabling "Channel mode" in the 'Wave convert' window.

[dBlues]

A simple way to get rid of DC-offset: as DC-offset is nothing but 0-frequency level (think of AC vs DC), you can apply a hi-pass filter VST to the master output. I usually set it to filter everything below 40Hz, this will generally improve sound clarity and stereo image.

[Sam_Zen]

DC-offset is nothing but 0-frequency level

Sorry, but you're simply wrong here. A DC-offset has nothing to do with the aspect of frequency.
Even a wave-frequency of 0.04 Hz or 2 MHz can have a DC-offset.

2 BooT-SectoR-ViruZ
Of course I use normalize in the wav-editor, but it would quite silly to do that first, before correcting a DC-offset.
In fact, normalisation is always the last effect I imply in the order of modifications.
Equalizing an already normalized file with some freq. boost is asking for distortions in the result.
But, as you said, this is off-topic here.

[dBlues]

DC-offset is nothing but 0-frequency level

Sorry, but you're simply wrong here. A DC-offset has nothing to do with the aspect of frequency.

I believe we both are speaking of the same thing. For me it is natural to think of 0-frequency "wave". Take 0.00000000001Hz wave for example, lets say you have recorded it. It completes its oscillation every 1/0.00000000001 = 100 000 000 000 seconds. That would seem like DC offset, you could hardly see the wave move.

Even a wave-frequency of 0.04 Hz or 2 MHz can have a DC-offset.

Of course. That is exactly why I would use a ~40Hz hi-pass filter to remove the DC offset.

[Saga Musix]

errr, even IF that methoed works, it's a COMPLICATED to use it. Plus, you lose some FREQUENCIES, which means that you lose SOUND. Removing a DC offset by "moving the shape a bit up or down" is much easier and doesn't alter the signal itself.