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Merged
mjwilson-google merged 7 commits into from
Oct 31, 2026
Merged

Specify DynamicsCompressorNode makeup gain control #2641

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9841eb9
Specify DynamicsCompressorNode makeup gain control
Aug 15, 2025
d04b637
Fix indentation
Aug 15, 2025
7c8429d
Revise based on notes
Oct 25, 2026
e73ebf4
Merge branch 'WebAudio:main' into makeup-gain
mjwilson-google Oct 27, 2026
12d0402
Merge branch 'WebAudio:main' into makeup-gain
mjwilson-google Oct 27, 2026
0709189
Merge branch 'WebAudio:main' into makeup-gain
mjwilson-google Oct 29, 2026
8fd086f
Merge branch 'WebAudio:main' into makeup-gain
mjwilson-google Oct 29, 2026
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104 changes: 91 additions & 13 deletions index.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -3480,7 +3480,7 @@ is called on.
factory method).

1. If <var>k</var> is the name of an {{AudioParam}} on this
interface, set the {{AudioParam/value}}
interface, then if <var>v</var> is of a [=numeric type=], set the {{AudioParam/value}}
attribute of this {{AudioParam}} to <var>v</var>.

2. Else if <var>k</var> is the name of an attribute on this
Expand Down Expand Up @@ -4248,8 +4248,9 @@ Attributes</h4>
{{DynamicsCompressorNode/threshold}},
{{DynamicsCompressorNode/knee}},
{{DynamicsCompressorNode/ratio}},
{{DynamicsCompressorNode/attack}}, and
{{DynamicsCompressorNode/release}}
{{DynamicsCompressorNode/attack}},
{{DynamicsCompressorNode/release}}, and
{{DynamicsCompressorNode/makeupGain}}
MUST be "{{AutomationRate/k-rate}}". <span
class="synchronous">An {{InvalidStateError}}
must be thrown if the rate is changed to
Expand Down Expand Up @@ -7886,6 +7887,27 @@ macros:
tail-time-notes: This node has a <a>tail-time</a> such that this node continues to output non-silent audio with zero input due to the look-ahead delay.
</pre>

<xmp class="idl">
enum MakeupGainOptions {
"automatic"
};
</xmp>

<div class="enum-description">
<table class="simple" dfn-type=enum-value dfn-for="MakeupGainOptions">
<caption>{{MakeupGainOptions}} Enumeration description</caption>
<thead>
<tr>
<th>Enum Value</th><th>Description</th>
<tbody>
<tr>
<td>
"<dfn>automatic</dfn>"
<td>
Set the makeup gain as described in [=Computing the makeup gain=].
</table>
</div>

<xmp class="idl">
[Exposed=Window]
interface DynamicsCompressorNode : AudioNode {
Expand All @@ -7897,6 +7919,7 @@ interface DynamicsCompressorNode : AudioNode {
readonly attribute float reduction;
readonly attribute AudioParam attack;
readonly attribute AudioParam release;
readonly attribute AudioParam makeupGain;
};
</xmp>

Expand All @@ -7907,13 +7930,26 @@ Constructors</h4>
: <dfn>DynamicsCompressorNode(context, options)</dfn>
::

Let <dfn attribute for="DynamicsCompressorNode">[[internal reduction]]</dfn>
be a private slot on <var>this</var>, that holds a floating point number, in
decibels. Set {{[[internal reduction]]}} to 0.0.

Let <dfn attribute for="DynamicsCompressorNode">[[automatic
makeup gain]]</dfn> be a private slot on <var>this</var>, that
holds a boolean. Set {{[[automatic makeup gain]]}} to `true`
if the {{DynamicsCompressorOptions/makeupGain}} option is
"{{MakeupGainOptions/automatic}}" or unspecified, otherwise set
it to `false`.

<pre class=include>
path: audionode-init.include
</pre>

Let <dfn attribute for="DynamicsCompressorNode">[[internal reduction]]</dfn>
be a private slot on <var>this</var>, that holds a floating point number, in
decibels. Set {{[[internal reduction]]}} to 0.0.
If {{[[automatic makeup gain]]}} is `true`, set the internal slot
{{AudioParam/[[current value]]}} of
{{DynamicsCompressorNode/makeupGain}} to the return value of
<a>computing the makeup gain</a>, <a
href="#linear-to-decibel">converted to decibel</a>.

<pre class=argumentdef for="DynamicsCompressorNode/constructor()">
context: The {{BaseAudioContext}} this new {{DynamicsCompressorNode}} will be <a href="#associated">associated</a> with.
Expand Down Expand Up @@ -7954,6 +7990,29 @@ Attributes</h4>
rate-notes: Has [=automation rate constraints=]
</pre>

: <dfn>makeupGain</dfn>
::
The decibel value of the makeup gain applied to the signal. If
{{[[automatic makeup gain]]}} is `true`, this {{AudioParam}}
cannot be modified; <span class="synchronous">an
{{InvalidStateError}} MUST be thrown if its
{{AudioParam/value}} attribute is set, if any [=automation
method=], {{AudioParam/cancelScheduledValues()}}, or
{{AudioParam/cancelAndHoldAtTime()}} is called on it, or if an
{{AudioNode}} is connected to it</span>.

<pre class=include>
path: audioparam.include
macros:
default: 0
min: <a>most-negative-single-float</a>
min-notes: Approximately -3.4028235e38
max: \(\approx 771\)
max-notes: This value is approximately \(20\ \log_{10} \mathrm{FLT\_MAX}\) where FLT_MAX is the largest {{float}} value.
rate: "{{AutomationRate/k-rate}}"
rate-notes: Has [=automation rate constraints=]
</pre>

: <dfn>ratio</dfn>
::
The amount of dB change in input for a 1 dB change in output.
Expand Down Expand Up @@ -8017,6 +8076,7 @@ constructing the node.
dictionary DynamicsCompressorOptions : AudioNodeOptions {
float attack = 0.003;
float knee = 30;
(float or MakeupGainOptions) makeupGain = "automatic";
float ratio = 12;
float release = 0.25;
float threshold = -24;
Expand All @@ -8028,19 +8088,25 @@ Dictionary {{DynamicsCompressorOptions}} Members</h5>

<dl dfn-type=dict-member dfn-for="DynamicsCompressorOptions">
: <dfn>attack</dfn>
:: The initial value for the {{DynamicsCompressorNode/attack}} AudioParam.
:: The initial value for the {{DynamicsCompressorNode/attack}} {{AudioParam}}.

: <dfn>knee</dfn>
:: The initial value for the {{DynamicsCompressorNode/knee}} AudioParam.
:: The initial value for the {{DynamicsCompressorNode/knee}} {{AudioParam}}.

: <dfn>makeupGain</dfn>
:: The initial value for the {{DynamicsCompressorNode/makeupGain}}
{{AudioParam}}. If set to "{{MakeupGainOptions/automatic}}", the
makeup gain will be calculated as described in [=Computing the
makeup gain=].

: <dfn>ratio</dfn>
:: The initial value for the {{DynamicsCompressorNode/ratio}} AudioParam.
:: The initial value for the {{DynamicsCompressorNode/ratio}} {{AudioParam}}.

: <dfn>release</dfn>
:: The initial value for the {{DynamicsCompressorNode/release}} AudioParam.
:: The initial value for the {{DynamicsCompressorNode/release}} {{AudioParam}}.

: <dfn>threshold</dfn>
:: The initial value for the {{DynamicsCompressorNode/threshold}} AudioParam.
:: The initial value for the {{DynamicsCompressorNode/threshold}} {{AudioParam}}.
</dl>

<h4 id="DynamicsCompressorOptions-processing">
Expand Down Expand Up @@ -8142,6 +8208,13 @@ values. Those values persist accros invocation of this algorithm.
sample-rate of the {{BaseAudioContext}} this
{{DynamicsCompressorNode}} is <a href="#associated">associated</a> with.

1. Let <var>makeup gain</var> be the return value of <a>computing
the makeup gain</a> if {{[[automatic makeup gain]]}} is `true`.
Otherwise, let <var>makeup gain</var> have the value of
{{DynamicsCompressorNode/makeupGain}}, [=decibels to linear gain
unit|converted to linear units=] and sampled at the time of
processing (as a <a>k-rate</a> parameter).

1. Let <var>detector average</var> be the value of the slot {{[[detector average]]}}.

1. Let <var>compressor gain</var> be the value of the slot {{[[compressor gain]]}}.
Expand Down Expand Up @@ -8183,8 +8256,7 @@ values. Those values persist accros invocation of this algorithm.
to <var>compressor gain</var>.

9. Compute <var>reduction gain</var> to be <var>compressor
gain</var> multiplied by the return value of <a>computing the
makeup gain</a>.
gain</var> multiplied by <var>makeup gain</var>.

10. Compute <var>metering gain</var> to be <var>reduction gain</var>, <a href="#linear-to-decibel">converted to
decibel</a>.
Expand All @@ -8200,6 +8272,12 @@ values. Those values persist accros invocation of this algorithm.

Note: This step makes the metering gain update once per block, at the
end of the block processing.

1. If {{[[automatic makeup gain]]}} is `true`, <a>atomically</a> set
the internal slot {{AudioParam/[[current value]]}} of
{{DynamicsCompressorNode/makeupGain}} to the value of
<var>makeup gain</var>, <a href="#linear-to-decibel">converted to
decibel</a>.
</div>

The makeup gain is a fixed gain stage that only depends on ratio,
Expand Down
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