Re: correct DC offset or uneven audio

Serge Auckland wrote:

"pb" <nobody@xxxxxxxxx> wrote in message news:Xns9AA24DDCE2470nobody@xxxxxxxxxxxxxxx
I corrected the DC offset so the base line is centered, but I can't really
hear the difference. Because the original baseline moved toward the
bottom, the bottom part was much shorter than the part above the baseline.
With that, you can't normalize it further. The volume is low since the
upper side is over the edge. How can the audio like this be further
enhanced?

I also found some recorded audio without DC offset problem but has a
little bit difference in length below and above the baseline. Is it
normal? What does it tell about the recording device?

Thanks for the help,

The instantaneous amplitude of any piece of audio will not be symmetrical about the base line in the short-term. Voice especially is asymmetrical, but so are many instruments. In the long-term, it all averages out provided of course there are no DC offset problems with the recording device. The issue is well recognised in Broadcast, especially AM, where it is possible to exceed 100% modulation in the positive direction, but not in the negative direction. Consequently, AM processors include phase rotators which ensure that the highest modulation is always positive. 125%, even 150% positive mod is possible where permitted by regulation (The UK does NOT allow more than 100% mod)

There's nothing to stop you exceeding 100% mod in the negative direction if you do it right, and recover with a synchronous demodulator. I've done it myself and recovered undistorted modulation.

When I say do it right, I mean using a double balanced mixer followed by a linear amp. Obviously you can't do it when modulating an output valve's anode.

d
.

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