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Re: DynamicsCompressorNode no automatic make up gain

From: Raymond Toy <rtoy@google.com>
Date: Mon, 7 Jul 2014 09:23:06 -0700
Message-ID: <CAE3TgXEZWP9+XNh3x+nBZm_R74m5M6+e+2YNuGZW48FEpwizOw@mail.gmail.com>
To: Robin Reumers <robinreumers@gmail.com>
Cc: "public-audio@w3.org" <public-audio@w3.org>
On Thu, Jul 3, 2014 at 7:18 PM, Robin Reumers <robinreumers@gmail.com>
wrote:

> Hi all,
>
> For educational purposes, I used the DynamicsCompressorNode to teach
> compression. However, the DynamicsCompressorNode in the Web Audio API uses
> some sort of automatic make up gain, so it’s not just compressing above a
> threshold, but actually taking the soft parts up.
>

I don't quite understand what this make-up gain is, but originally the
DynamicsCompressor node had an emphasis and de-emphasis filters for high
freuqencies that would cause the compressed audio to have a gain applied.
 See the discussion at
http://lists.w3.org/Archives/Public/public-audio/2014JanMar/0010.html.

If this is what you are seeing, then this should have been removed and
Chrome 36 should have this fix.



> For education, it’s important, that I can show this manually to my
> students, so compression is basically taking the down the signal, above the
> threshold, by the ratio. Then using a manual make up gain, I can offset why
> I just compressed and bring all the levels up.
>
> Is there a way to turn off the automatic make up gain added by the
> DynamicsCompressorNode? I tried linking the reduction meter with a gain
> offset and doing the exact opposite gain of the reduction, but this only
> results in glitches and I can’t get it to work properly.
>
> Any ideas would be welcome.
>
> Best wishes,
>
> Robin
>
Received on Monday, 7 July 2014 16:23:35 UTC

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