Re: [Audacity-devel] Normalize only works up to -24db?

[Michael C. <mc...@gm...>]

Sorry, I forgot to include an explanation.

mLevel is in (apparently) negative db.

to convert db to a ratio, you do 10^(db/20).

I also don't know why we multiply by 10 and then divide by 200 instead
of just dividing db by 20 like usual - is there some trick or gotcha
here?


On Fri, Nov 21, 2008 at 12:27 AM, Michael Chinen <mc...@gm...> wrote:
> I found this behavior a bit odd.  The code in
> EffectNormalize::StartProcessing() explains why this is happening.
>
>  NORMALIZE_DB_MIN is -240, but because mLevel is multiplied by 10, it
> means 24 db, not -240db.
> Is there a good reason or convention that says you should limit
> normalize at 24db?  In any case, we don't notify the user of the
> truncation.
>
>   float ratio = pow(10.0,TrapDouble(-mLevel*10,
>                                     NORMALIZE_DB_MIN,
>                                     NORMALIZE_DB_MAX)/200.0);
>