Re: Creating files with RMS gain level instead of Peak

["Måns Rullgård" <mans@mansr.com>]

Jeremy Nicoll - ml sox users <jn.ml.sxu.88@wingsandbeaks.org.uk> writes:

> On 2018-07-07 19:19, Måns Rullgård wrote:
>> Jeremy Nicoll - ml sox users <jn.ml.sxu.88@wingsandbeaks.org.uk> writes:
>>
>>> On 2018-07-07 16:05, James Trammell wrote:
>>>
>>>> How can I get gain of -12dBFS RMS?
>>>
>>> I don't understand the difference, but even I can see
>>> that the manual describes -B and -b options for the
>>> gain effect, in terms of RMS rather than peak levels.
>>>
>>> I do not know if one or other of these options will do
>>> what you want.
>>
>> Those options are for equalising channels using either peak or RMS
>> value as reference.
>
> Ah, I read about the equalising and then forgot it...
>
>> For a fixed scaling, the peak and RMS values are affected equally.
>> Dividing every sample by two, say, will halve both the peak and RMS
>> values.
>
> Yes.  So does that mean that the OP should use something like the
> 'stat' effect to find out the peak RMS level of the audio file,
> then work out how much gain or attenuation is needed, then use
> a 'gain' effect with that calculated value?

No, he should just use the gain effect.  It adjusts both RMS and peak
values by the same amount because that is what happens when you multiply
each sample by a fixed amount, which is what the gain effect does.

The channel equaliser has both options because the crest factor is
unlikely to be exactly the same for all channels, so the gain required
to match the peaks won't be the same as that for matching the RMS
values.

-- 
Måns Rullgård

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