Turtlerock Forum

Can someone please explain what the hell is happening in this photo...

I don't understand what could cause what I am seeing...

Thanks,

Smash.

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Simon "Smash" Ashby

Parallel dimension?

Das Gamun ist kerplunken to ze leften?

It's an Audio Phase scope...

A vertical line means L&R are perfectly in phase (i.e. Mono),
A 45 degree line to the "L" means that there is only a L channel present,
A 45 degree line to the "R" means that there is only a R channel present,
A horizontal line means L&R are totally out of phase...

However in ALL of the above scenarios, the Audio still passes through the "0" point in the middle of the scope...

I've never ever seen audio not pass through the 0 point in the centre like that.

I'm wondering what it is, what could be causing it, and whether or not I need to reject it!

Simon "Smash" Ashby.

ok, being serious for a moment... if this was a traditional CRO, my first thought would be an offset/calibration issue. Have you tried firing test tones at it?

But as you say, regardless of the nature of the signal, it should always pass through zero... which is why I would query some sort of offset problem.

I don't think it's a calibration issue...

The image in question comes from a 30 second segment that forms part of a larger package.

THe rest of the package meters normally, as do bars & tone, it's only the one segment that is generating the weird scope response.

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Simon "Smash" Ashby

First thought is a calibration issue, but if the scope has a response down to DC, would you get this display?
Is it analog or digital in?

It's a Digital In, it's actually De-embedding the audio from an HD-SDI video signal.

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Simon "Smash" Ashby

Well it's obviously dual mono so if its supossed to be stereo
It's not
I would think there is a dc offset issue which is happening at the same
Time so the scope is reading the dc and the audio and its unhappy

Or simply that the scope is out of alignment digital or not
It will have an adjustment ..somewhere

What's it sound like ?

Nah, it's just that un-shielded speaker you have next to the screen pulling the trace sideways...

OK...

Fixed it.

Put a stacked series of High Pass filters on it at 40 Hz. I figured if it was going down to DC, then I could e.q. it out.
It worked

Now for the second part of the question - how the hell did it happen?

It was just a voice over with some really light music underneath it...

The mic should have gone straight into the camera, then apparently edited (I'm assuming in FCP) and the file was delivered to my guy who dropped it into the package.

How do you get a VO to go down to DC?


Simon "Smash" Ashby

Happens all the time
Somebody didn't Install a computer card properly or it's half inserted
Any number of things that can make dc go looking for somewhere else to play
and its often the dc of the computers power supply that is to blame
And it way into the analog stage of the system

It's better then it use to be .. But sure it happens all the time
And your lucky you have a pretty picture to look at to see it

Typical symptoms are strange thumps when your trying to edit
In and out of silence