weird waveform

Posted: Sun Jul 13, 2008 9:57 pm

I recently mixed down a song that I have been working on and noticed that the waveform of the mix looks totally jacked. It basically looks like this... it looks like the waveform fell off or "melted" off of what would normally be the "center-line" of the wave. The mix sounds O.K. (not perfect or great or anything, but not audibly as jacked as the wave looks)... what's up? What did I do? How do I fix it?

Posted: Mon Jul 14, 2008 12:32 am

I don't know about you, But I LISTEN to music.

Post an example please.

Posted: Mon Jul 14, 2008 3:31 am

sound pretty much like dc offset?? but yeah might post a pic or something

Posted: Mon Jul 14, 2008 5:28 am

Greener wrote:

I don't know about you, But I LISTEN to music.

Post an example please.

I had the exact same thing happen to me a few weeks ago. I tried this technique to solve it, but after I listened to it, it still looked exactly the same Confused

I think a different solution might be in order.

btw, it does sound like DC offset to me as well, I just don't know how to fix it yet.

Posted: Mon Jul 14, 2008 6:33 am

Depends what the waveform was of, as well. Some instruments with very hard attack, like trumpets, for instance, can often look just like that. It may not be anything to worry about. What does it sound like?

Posted: Mon Jul 14, 2008 8:36 am

The OP mentioned that the song was mixed down, so it would not be an individual instrument.

The problem with the "what does it sound like" kind of question is that you probably would not hear DC offset. But just because you cannot hear it does not mean it is not a problem. It becomes a problem when you try to get the track up to a decent level.

One solution to the problem is to set a HPF at 20-30hz, really steep. I have not tried this yet, but I did sleep at a Holiday Inn last night, so it might work.

Good luck

Posted: Mon Jul 14, 2008 7:15 pm

Here is a picture of the waveform...

I looked up DC offset and it looked like that is when the "Center-line" shifts but the waveform is still symmetrical. As you can see, the waveform isn't symmetrical, it looks like something cut off the top half.

I can't hear anything in the mix that matches what I am seeing.... not that the mix is perfect or anything.

I'm not even sure I should worry about it. I normally don't pay too much attention to how the waveform looks, but this was so drastic I had no choice but to notice.

edit:
Here's a link to the mp3
the mix

Posted: Mon Jul 14, 2008 8:53 pm

This happens with some instruments. Even some voices are like this that I've seen.

Posted: Mon Jul 14, 2008 10:17 pm

Codemonkey wrote:

This happens with some instruments. Even some voices are like this that I've seen.

But the whole mix? None of the individual waveforms looked like this (drums, vox, guitars, bass)....

Maybe I shouldn't worry about it?

Posted: Mon Jul 14, 2008 10:21 pm

DC offset, means w/e u recorded this with doesnt like your computers mic input on the back

Posted: Mon Jul 14, 2008 11:03 pm

multoc wrote:

DC offset, means w/e u recorded this with doesnt like your computers mic input on the back

I recorded most of it with a Firepod (acoustic, electric, bass, vox)... and the drums through a digi 002 (I think.... recorded a friend at his place).... so I don't see how the mic input on my comp. would make a difference. Please elaborate.

Posted: Tue Jul 15, 2008 4:12 am

I could believe a single mic channel could look like this (although I would say the polarity is the reverse of normal), but a mix of several channels, no. There's something not right there. It looks like a compresser is working on only the positive half of the waveforms.

Try mixing it again with all the input channels phase-flipped but nothing else changed. If the mix picture inverts so that it is predominantly in the positive half, then all is OK. If the result looks much the same as now, you need to start trouble-shooting.

Posted: Tue Jul 15, 2008 5:51 am

I'm only listening on a lappy, but I can't hear anything drastic in that. Good singing, BTW. You?

Posted: Wed Jul 16, 2008 3:49 am

hackenslash wrote:

I'm only listening on a lappy, but I can't hear anything drastic in that. Good singing, BTW. You?

Thanks, yeah that is me.

Well, I think I fixed it...

I took the track to a friend who has Adobe Soundbooth CS3 today and ran the "remove noise>rumble" filter (saw this as a fix when I was searching for dc offset... I'm guessing I could have used the HP filter like someone suggested earlier). Anyway, I applied the filter and now the waveform looks normal (doesn't really sound different to my ear). So I guess it was DC offset on the entire mix.... weird.

Thanks for all your help everyone...

Posted: Wed Jul 16, 2008 7:03 am

No, I don't think that was DC Offset. Something like that could only happen with DC Offset, I reckon, if there were a different amount of offset from track to track before mixdown. I could be wrong about this, as I'm just spitballing. In any event, it would be a simple matter to check. Simply remove DC Offset on all your constituent tracks and then run the mixdown again.

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