AC-3 amplification calculation

[Josip Tosic]

Hi,
I was wondering it there's a tool out there that'll open 5.1 AC-3, calculate how much I need to amplify the audio and, preferably, show the value in percents so I can use that value in VirtualDubMod's "Volume" feature?

[Illusion]

I haven't found a utility, but I do it using SOX when going from AZID output to OGGENC. AZID converts AC3 streams and gives maximum signal levels in dBV (listed as dB).

Take a look at the channel output info at the end of processing the AC3 and (for AZID) it will tell you what the maximum signal level is (a dB value like -8.1 dB) on each channel and the largest overall.

Use the largest overall signal level and negate it, to make it positive, divide by 20, then take the AntiLOG. That's the amplification factor you need to go full scale.

So: ALOG(-(dbV)/20) = scale factor
and %Volume increase = scale factor * 100

Good luck,
Doug

[Josip Tosic]

Thanks! Works like a charm!