Distorted audio help - high profile concert recording

tkhansen  wrote I know there is often not much that can be done to repair distorted audio, but my knowledge here is quite limited.

Let me extend it slightly for you; there is nothing that can be done to repair distorted audio accurately at all, as you have no reference points as to what the signal should actually contain. Without this, you are comprehensively stuffed, I'm afraid.

So what's really going on here? I looked at the reviews for this camera, and whilst they all went on about how wonderful the pictures were, nobody mentioned the sound at all. That should tell you something...

What you have here is a mic that has completely overloaded the first preamp stage, and that's where the clipping is. You can tell this because the tops aren't actually flat, but sloping, and on the face of it, this reveals that the preamp isn't fully driving the A-D converter. In other words, the gain staging inside the camera isn't correct, and you'll never be able to use all of the available dynamic range, whatever you do. And, like most if not all cameras like this, you won't be able to alter the preamp gain - it's fixed. So even if you manage to fit an attenuator to the mic and manage not to overload the input, it's still not going to be too great a result.

This is why Tascam and Zoom sell those little 4 channel recorders with a camera fitting on top of them. They let you make a much better recording, and send a low-level reference-only version of it to the camera, just for syncing purposes. I'd strongly recommend that you think about getting one of these!

I'm afraid that is unrecoverable damage.  If you zoom in, you'll see that nearly every single cycle is clipped into a nearly flat waveform.  Short of redrawing every single peak by hand, I see no way to fix it.  The overall level is below zero (hovering around -6dBFS) so the problem was ahead of the final stage of recording. Possibly the mic itself overloading.