Hej,
just recognized today something that seems strange to me: When I bounce my softsynths in Logic or in Pro Tools, I sometimes get DC-Offset in the resulting audio-file. Why is that? Like when I'm using the init-patch in Zebra, play some chords and bounce that out, I get 0,001% DC Offset.
Is that correct and expected? Different synths and different patches give different results, but still there's this offset. Does anyone know the cause for this?
Thanks
Jan
DC-Offset when bouncing - why?
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- KVRAF
- 3229 posts since 10 Nov, 2013 from Germany
A tiny bit of DC is always expected.
I tried to reproduce in Repear, but I can see nothing to complain about.
The sound fades down to -100 dB after some seconds.
I tried to reproduce in Repear, but I can see nothing to complain about.
The sound fades down to -100 dB after some seconds.
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- KVRer
- Topic Starter
- 21 posts since 5 Sep, 2016
Okay, but why is it expected? I don't see, why a DC-offset is there in my softsynths. I don't have any offset when recording Audio through my interface. My hardware-synths don't have any dc-offset. But the softsynths have it. Logic measures it; RX does the same. Why?
I know it's a tiny amount and nothing to worry about too much, but still I'm curious why this happens and why it isn't possible in software-land to get rid of any offset in the first place.
I know it's a tiny amount and nothing to worry about too much, but still I'm curious why this happens and why it isn't possible in software-land to get rid of any offset in the first place.
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- KVRian
- 814 posts since 18 May, 2007 from Berlin
I also don't see why this should be expected, but I am no developer.
[EDIT: See new details in a later post]
And I don't have any DC offset here when I play with Zebra's init preset.
Can you describe how you're determining the offset? Do you see a line in the silent part that is slightly apart from the zero line? You could check wether you have any audio inputs active during recording too, just to be sure that there's nothing else influencing the render.
Viktor
[EDIT: See new details in a later post]
And I don't have any DC offset here when I play with Zebra's init preset.
Can you describe how you're determining the offset? Do you see a line in the silent part that is slightly apart from the zero line? You could check wether you have any audio inputs active during recording too, just to be sure that there's nothing else influencing the render.
Viktor
Last edited by Viktor [TUC] on Tue Apr 25, 2023 11:44 am, edited 1 time in total.
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- KVRer
- Topic Starter
- 21 posts since 5 Sep, 2016
Right, I just get a dc-reading in Logics audio-editor when I check the bounce-in-place.
RX is telling me the same. 0,001%. I mean, it's tiny, I know. Someone told me that this isn't "real" dc-offset, just a waveform that isn't perfectly balanced.
But what is it? And why is it there?
RX is telling me the same. 0,001%. I mean, it's tiny, I know. Someone told me that this isn't "real" dc-offset, just a waveform that isn't perfectly balanced.
But what is it? And why is it there?
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- KVRian
- 814 posts since 18 May, 2007 from Berlin
Ah, I thought you were seeing actual DC Offset, like the "silent" part not being at the zero line. That's not the case here.
I'm not 100% sure how DC Offset is calculated but they must take some sort of average between the amplitudes of samples on both sides of the zero line, and if across the whole audio clip the average amplitude leans towards top or bottom, you'll get a non-zero value for DC Offset. A few larger values in any part of the waveforms might already throw this off. Nothing to worry about.
I checked a whole lot of synth recordings just now, plus other recorded audio material, and most show these small DC offset values in iZotope RX. This isn't u-he related.
Viktor
I'm not 100% sure how DC Offset is calculated but they must take some sort of average between the amplitudes of samples on both sides of the zero line, and if across the whole audio clip the average amplitude leans towards top or bottom, you'll get a non-zero value for DC Offset. A few larger values in any part of the waveforms might already throw this off. Nothing to worry about.
I checked a whole lot of synth recordings just now, plus other recorded audio material, and most show these small DC offset values in iZotope RX. This isn't u-he related.
Viktor
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- u-he
- 30204 posts since 8 Aug, 2002 from Berlin
If you create audio recordings using DC coupled ADCs, you'll inevitably get DC offsets. If you use AC couple ADCs you can still get DC offsets if the beginning or end start without any crossfade from zero.
The DC offsets simply occurr due to a very few random samples at the beginning or end of a recording, and in thew case of softsynths of the amplitude envelope. If a softsynths has a DC blocker (highpass filter) at say, 1 Hz, you need a very long attack and release phase to ensure that no DC offset at all is measurable. (Some synths may not DC block at all, and this is even requested sometimes, so... there a DC would absolutely be expected and hard to avoid...)
Also, depending on how things measure this, the shorter the clip, the larger the impact of a few random samples on the overall DC offset.
I do not think this is anything to worry about.
The DC offsets simply occurr due to a very few random samples at the beginning or end of a recording, and in thew case of softsynths of the amplitude envelope. If a softsynths has a DC blocker (highpass filter) at say, 1 Hz, you need a very long attack and release phase to ensure that no DC offset at all is measurable. (Some synths may not DC block at all, and this is even requested sometimes, so... there a DC would absolutely be expected and hard to avoid...)
Also, depending on how things measure this, the shorter the clip, the larger the impact of a few random samples on the overall DC offset.
I do not think this is anything to worry about.
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- KVRian
- 814 posts since 18 May, 2007 from Berlin
You know what happens when you select that "remove" function on that whole clip like in the screenshot above?
Logic simply shifts the whole thing upwards or downwards, creating actual DC offset in the process.
Meaning, it has its flaws and you'd really have to know how best to use and when to avoid it if you don't want to create more problems in your audio clip.
Viktor
Logic simply shifts the whole thing upwards or downwards, creating actual DC offset in the process.
Meaning, it has its flaws and you'd really have to know how best to use and when to avoid it if you don't want to create more problems in your audio clip.
Viktor
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- KVRer
- Topic Starter
- 21 posts since 5 Sep, 2016
Right, thanks Victor and Urs. It really helped me to understand what's behind these numbers, and I will no longer worry about it.
Funny though that Logics remove-function seems to do the "wrong" thing with these kind of files. It may be the right thing for actual dc-offsets.
Cheers
Jan
Funny though that Logics remove-function seems to do the "wrong" thing with these kind of files. It may be the right thing for actual dc-offsets.
Cheers
Jan