DC Offset

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SteelyDani
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DC Offset

Post by SteelyDani » Mon Feb 25, 2019 7:46 pm

I’ve made a mix and opened the Statistics tab for analyzing it. The DC Offset is 1.90% (left channel) and 1.89% (right channel). Being these figures very high I’ve repeated the analysis of the same file but in WaveLab which shows a much more reasonable DC Offset of 0.0830% (left channel) and 0.0832 (right channel).

To be sure I've repeated the whole process several times. The figures in both programs remain changeless.

What am I doing wrong?
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2019-02-25.png
Cubase 10
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2019-02-25 (1).png
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Elien
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Re: DC Offset

Post by Elien » Mon Feb 25, 2019 7:52 pm

Well, I cant explain the difference between the two results - the question is do both programs use the same algorithm for calculating the DC offset?

The DC offset might be introduced by the AD-Converters or external gear. Or it is "imported" by using samples that carry a dc offset within themselves.

BR, Ernst
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valvehead
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Re: DC Offset

Post by valvehead » Mon Feb 25, 2019 8:00 pm

I suspect that Cubase is calculating the percentage incorrectly. Notice that the amounts in dB are the same for both. For example the left channel shows -61.62dB which does equate to 0.083%.
Cubase 10 Pro, Wavelab 9.5 Pro
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SteelyDani
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Re: DC Offset

Post by SteelyDani » Mon Feb 25, 2019 8:23 pm

You're right, although it seems very weird. Bad Cubase calculation? No one has noticed it so far?
http://www.bcstudiorecording.com
BCS. Basque Coast Studio
Music is a gift from God to Man

Windows 10 (64)/ Cubase Pro 9.5/ WaveLab 9.5 Elements/ Halion 6 / Intel(R) I7-6700K @ 4.00 GHz - 32GB Dual Channel DDR4/ MOTU PCI-424 + 4 X 2408 mk3

valvehead
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Re: DC Offset

Post by valvehead » Mon Feb 25, 2019 10:09 pm

Apparently this has been the case for a long time. I just generated a test file with nothing but DC offset. The left and right channels are constant at 50% and 25% (-6.02dB and -12.04dB respectively).

Wavelab and Audition both report the correct values. Cubase 4, 9.5, and 10 all show 100% on both channels, but the values in dB are correct.

I also tried an ordinary audio file and found a large discrepancy between Cubase and other programs, but it wasn't off by the same factor as SteelyDani's post.

Now that I'm thinking about it, perhaps Cubase is calculating DC as the percentage of the RMS level (square wave) of the file instead of full scale. That would explain why my DC test file showed 100% on both channels. If this is the case, why isn't that applied that to the decibel values? :?:

I'll try some more tests with varying AC and DC content.
Attachments
Statistics WaveLab 9.5.png
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Statistics Cubase 10.png
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Statistics Audition 3.png
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Last edited by valvehead on Mon Feb 25, 2019 10:26 pm, edited 1 time in total.
Cubase 10 Pro, Wavelab 9.5 Pro
Windows 10 Pro 1903, Intel i7 5820k, Gigabyte X99 Gaming G1, Corsair DDR4 32GB, Samsung 960 Pro 512GB
RME Fireface 800, Dynaudio BM6a

valvehead
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Re: DC Offset

Post by valvehead » Mon Feb 25, 2019 10:24 pm

Here's Audition set to calculate RMS referenced to FS square wave including DC.

Also attached is the DC test file. It's amusing how compact the zip file is compared to the original file. :mrgreen:
Attachments
DC offset.zip
(35.28 KiB) Downloaded 29 times
Statistics Audition 3 sq wave RMS.png
(10.62 KiB) Not downloaded yet
Cubase 10 Pro, Wavelab 9.5 Pro
Windows 10 Pro 1903, Intel i7 5820k, Gigabyte X99 Gaming G1, Corsair DDR4 32GB, Samsung 960 Pro 512GB
RME Fireface 800, Dynaudio BM6a

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