Mixing/Recording Commentary into Source Audio

[WakkoBlues]

I have a voice only commentary track...and I am interesting in finding a way to mix it into the original audio in such a way that the volume fades/ducks on the original when the commentary is speaking.

It needs to be automatic, as I already have the commentary track recorded.

Anyone have any ideas at all? I've been messing around with Sony Vegas and Sound Forge, and so far I don't see anything that can do this (granted there is a lot to explore and I am still playing around).

Again, any suggestions at all would be greatly appreciated.

[AlanHK]

I used Audacity.

If you have the time, you can use the envelope tool to mute the primary soundtrack when the commentary came on, but I did this once and it was a lot of work.

I found this satisfactory and much faster:

Copy the original soundtrack and use:
Effect: Compressor, and set Threshold at about -30 dB, and Ratio at the maximum, 10:1.
UNcheck "Normalize" (otherwise it will boost the volume back up).

This reduces the dynamic range, especially loud sections like music, explosions, etc., and reduces the maximum volume.

Then I load the commentary track.

Just listen to these together and if the original soundtrack is too loud, undo the effect and make the Threshold lower, reapply.
(I normally select a short passage where it's loud, a few seconds, to quickly apply and undo the effect till I'm happy with the result, then undo the last one, and select all, apply.)

You can visually inspect the waveform and check the sections where the soundtrack is particularly loud to be sure the commentary is audible.

This is pretty quick once you get an idea of how the filter works.

Then export to wave, convert to AC3 in ffmpeg.

Though obviously the original soundtrack won't be clear at all times, you can still follow it and it's much better than the commentary over dead silence.

If you can get subtitles, these help to orient you when you have the commentary track on.

[WakkoBlues]

Thank you, I will do that if I can't figure out how to get some sort of automatic volume envelope generated.

Anyone know of any plugins that can help?

[Greensold]

Not looking for a bump, but I came across these posts on a Google search and the question went unanswered.

I found out that the Audacity plugin "Auto Duck" does exactly what we need here: http://audacityteam.org/manual/index.php?title=Auto_Duck

It's built in to Audacity Posted for future searchers.

[AlanHK]

I found out that the Audacity plugin "Auto Duck" does exactly what we need here

I had thought it was a novelty effect to make you sound like a duck...

I tried it and it does work.
However, it is incredibly slow. It took well over an hour to process a 45 minutes audio project with two tracks.
Using Compressor took only about 3 minutes. So I reverted to Compressor.