Bug 78937 – Implement static compression curve parameters for DynamicsCompressorNode

• Component: New Bugs
• Status: RESOLVED FIXED

[Chris Rogers]

Implement static compression curve parameters for DynamicsCompressorNode

[Chris Rogers]

Created attachment 127665 [details]
Patch

[Chris Rogers]

Dynamic range compression has parametric control of the static compression curve:
threshold: the dB value above which the compression will start taking effect
knee: historically this has often been simply "hard" or "soft" knee, but this is a value (in dB) representing the range above the threshold where the curve smoothly transitions to the "ratio" portion
ratio: this value represents the amount of dB change in input for a 1 dB change in output

The "reduction" parameter is a read-only value for metering purposes, representing the current amount of gain reduction that the compressor is applying to the signal

[Chris Rogers]

Here's an interactive graphing app to show the parametric curve:
http://chromium.googlecode.com/svn/trunk/samples/audio/compression-curve2.html

[Chris Rogers]

Created attachment 128832 [details]
Patch

[Kenneth Russell]

Comment on attachment 128832 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=128832&action=review

This looks fine per your walking through the algorithm with me offline. A couple of minor nits. r=me

> Source/WebCore/platform/audio/DynamicsCompressor.cpp:58
> +    if (parameterID < ParamLast)

Is this worth an ASSERT?

> Source/WebCore/platform/audio/DynamicsCompressorKernel.cpp:174
> +        k = sqrt(minK * maxK);

sqrtf?

> Source/WebCore/webaudio/DynamicsCompressorNode.idl:33
> +        readonly attribute AudioParam reduction; // in Decibels

I assume these changes are being specified?

[Chris Rogers]

Committed r109023: <http://trac.webkit.org/changeset/109023>