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Author Topic: Fixing DC offset  (Read 6362 times)

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Offline jerrythek

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Fixing DC offset
« on: March 27, 2007, 06:15:41 PM »
There's a dedicated command for fixing DC offset within the AudioGate software - try it out.

Regards,

Jerry
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Offline Gordon

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Re: Fixing DC offset
« Reply #1 on: March 28, 2007, 03:41:46 AM »
can some one explain in 1st grade language what dc offset is and why we should fix it?  and yes I've "googled it" and still have no clue about it.
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Offline Dede2002

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Re: Fixing DC offset
« Reply #2 on: March 28, 2007, 09:14:35 AM »
Quote from: Gordon on March 28, 2007, 03:41:46 AM
can some one explain in 1st grade language what dc offset is and why we should fix it?  and yes I've "googled it" and still have no clue about it.


Yes! What is DC offset?  ???
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Offline cleantone

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Re: Fixing DC offset
« Reply #3 on: March 28, 2007, 01:41:58 PM »
I'm no expert (though I play one in real life)...

To my understanding it is when the zero VU reference is off (+ or -) from true zero. This would over or under extend the compressions and rarefactions that form a waveform. I am not sure of the cause but I think it is electrical somehow. I'd love to hear more...
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Offline Church-Audio

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Re: Fixing DC offset
« Reply #4 on: March 28, 2007, 02:34:04 PM »
Quote from: Gordon on March 28, 2007, 03:41:46 AM
can some one explain in 1st grade language what dc offset is and why we should fix it?  and yes I've "googled it" and still have no clue about it.

Dc offset is a DC voltage that is present in a AC voltage signal.

Its not good thing and it can be reduced by the use of a high pass filter at 15-20hz this can get rid of most of it. The problem with having a DC offset in a audio signal is that when you go to normalize the signal it will not be at its maximum amplitude because of the presence of this DC voltage. When you go and use the DC offset control in your program your just zeroing out this voltage. This should always be done before any audio editing is done.

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Offline Dede2002

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Re: Fixing DC offset
« Reply #5 on: March 30, 2007, 11:29:29 PM »
Quote from: Church-Audio on March 28, 2007, 02:34:04 PM
Quote from: Gordon on March 28, 2007, 03:41:46 AM
can some one explain in 1st grade language what dc offset is and why we should fix it?  and yes I've "googled it" and still have no clue about it.

Dc offset is a DC voltage that is present in a AC voltage signal.

Its not good thing and it can be reduced by the use of a high pass filter at 15-20hz this can get rid of most of it. The problem with having a DC offset in a audio signal is that when you go to normalize the signal it will not be at its maximum amplitude because of the presence of this DC voltage. When you go and use the DC offset control in your program your just zeroing out this voltage. This should always be done before any audio editing is done.



Thanks a lot, Chris! :D
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Offline taper420

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Re: Fixing DC offset
« Reply #6 on: April 12, 2007, 01:03:03 PM »
Is this a DC offset?
I ran CA cards > 9100 preamp > MT (line in)
The waveform looks strangely lopsided....

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Offline Church-Audio

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Re: Fixing DC offset
« Reply #7 on: April 12, 2007, 01:05:36 PM »
Quote from: taper420 on April 12, 2007, 01:03:03 PM
Is this a DC offset?
I ran CA cards > 9100 preamp > MT (line in)
The waveform looks strangely lopsided....



It might be try putting in a high pass filter at 20hz and then resave the file and reopen it. Maybe that will help.. You can always save a backup file.

I wish I knew but atleast left and right look very well matched level wise.
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Offline taper420

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Re: Fixing DC offset
« Reply #8 on: April 12, 2007, 01:16:01 PM »
Thanks for the help chris...
Doesn't seem like it.... the high-pass at 20hz didn't change the look of the waveform at all

Is there anything else that could cause waveforms to be lopsided?
I'll have to test to see at what point in the chain this is being introduced, unless it's what the waveforms are suppose to look like...
I don't know...I'm used to seeing music, and this is speech so maybe it's just the nature of the beast.
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Offline Church-Audio

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Re: Fixing DC offset
« Reply #9 on: April 12, 2007, 01:16:54 PM »
Quote from: taper420 on April 12, 2007, 01:16:01 PM
Thanks for the help chris...
Doesn't seem like it.... the high-pass at 20hz didn't change the look of the waveform at all

Is there anything else that could cause waveforms to be lopsided?
I'll have to test to see at what point in the chain this is being introduced, unless it's what the waveforms are suppose to look like...
I don't know...I'm used to seeing music, and this is speech so maybe it's just the nature of the beast.

I dont know.... I wish I did, how does it sound?
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Offline taper420

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Re: Fixing DC offset
« Reply #10 on: April 12, 2007, 01:21:29 PM »
Sounds normal....I'm not sure what I'm suppose to be hearing different though.
The lopsidedness simply limits the amount of gain I can put on it in post.
Which isn't that big of a problem, just trying to get to the bottom of this.....
...hmm, could a week battery on the preamp somehow introduce an offset like this?
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Offline taper420

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Re: Fixing DC offset
« Reply #11 on: April 12, 2007, 01:25:32 PM »
I think I figured it out.... it's just something weird about my voice..... I looked at some other VO waves I did on a totally different setup (shotgun > DV cam) and they are even more lopsided.
I think I'm going to dub this phenomenon "the taper420 offset"

« Last Edit: April 12, 2007, 01:29:55 PM by taper420 »
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Offline Church-Audio

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Re: Fixing DC offset
« Reply #12 on: April 12, 2007, 01:26:31 PM »
Quote from: taper420 on April 12, 2007, 01:25:32 PM
I think I figured it out.... it's just something weird about my voice..... I looked at some other VO waves I did on a totally different setup (shotgun > DV cam) and they are even more lopsided.
I think I'm going to dub this phenomenon "the taper420 offset"

Wow can we call you OFFSETMAN! ?
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Offline taper420

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Re: Fixing DC offset
« Reply #13 on: April 12, 2007, 01:36:23 PM »
Look there... in the wav... is it caused by DC?
No....it's OFFSETMAN.... able to offset waves with a single word.
Keep em away from your rig... or he might offset YOU!
Your high-pass can't stop him.... you have no filters strong enough....he will make normalizing impossible.....MUhahahaHAHAH!
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Offline Church-Audio

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Re: Fixing DC offset
« Reply #14 on: April 12, 2007, 01:40:07 PM »
Quote from: taper420 on April 12, 2007, 01:36:23 PM
Look there... in the wav... is it caused by DC?
No....it's OFFSETMAN.... able to offset waves with a single word.
Keep em away from your rig... or he might offset YOU!
Your high-pass can't stop him.... you have no filters strong enough....he will make normalizing impossible.....MUhahahaHAHAH!


Ok you have to stop with this shit now, ;D I have to clean up my monitor I spit out my coffee dammit....  ;D
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