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Specify render quantum size range #2667

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38 changes: 32 additions & 6 deletions index.bs
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Expand Up @@ -2381,6 +2381,8 @@ Dictionary {{AudioContextOptions}} Members</h5>
<code>"default"</code> is passed, or to ask the User-Agent to pick a good
<a>render quantum size</a> if <code>"hardware"</code> is specified.

See [[#render-quantum-sizes]] for the required supported range.

It is a hint that might not be honored.
</dl>

Expand Down Expand Up @@ -2508,16 +2510,20 @@ Constructors</h4>
1. Set the {{[[rendering thread state]]}} for
|c| to <code>"suspended"</code>.

1. Determine the {{[[render quantum size]]}} for this {{OfflineAudioContext}},
based on the value of the {{OfflineAudioContextOptions/renderSizeHint}}:
1. Set the {{BaseAudioContext/sampleRate}} for |c|,
based on the value of <code>contextOptions.{{OfflineAudioContextOptions/sampleRate}}</code>.

1. Determine the {{[[render quantum size]]}} for |c|,
based on the value of the <code>contextOptions.{{OfflineAudioContextOptions/renderSizeHint}}</code>:

1. If it has the default value of <code>"default"</code> or
<code>"hardware</code>", set the {{[[render quantum size]]}} private
slot to 128.

1. Else, if an integer has been passed, the User-Agent can decide to
honour this value by setting it to the {{[[render quantum size]]}}
private slot.
1. Else, if an integer has been passed, a {{NotSupportedError}} MUST be
thrown if the value is outside the range specified in
[[#render-quantum-sizes]], otherwise set the {{[[render quantum size]]}}
private slot to the passed value.

1. Construct an {{AudioDestinationNode}} with its
{{AudioNode/channelCount}} set to
Expand Down Expand Up @@ -2814,7 +2820,8 @@ Dictionary {{OfflineAudioContextOptions}} Members</h5>
: <dfn>renderSizeHint</dfn>
::
A hint for the <a>render quantum size</a> of this
{{OfflineAudioContext}}.
{{OfflineAudioContext}}. See [[#render-quantum-sizes]]
for the required supported range.
</dl>

<h4 interface lt="OfflineAudioCompletionEvent" id="OfflineAudioCompletionEvent">
Expand Down Expand Up @@ -11943,6 +11950,25 @@ inclusive. A {{NotSupportedError}} MUST be thrown if a sample rate outside this
range is specified.
</p>

<h3 id="render-quantum-sizes">Supported Render Quantum Sizes</h3>

<p>
Implementations MUST support {{BaseAudioContext/[[render quantum
size]]}} between 1 sample frame and 6 times the context sample rate,
inclusive, rounding down to the nearest integer if 6 times the context
sample rate is not an integer. A {{NotSupportedError}} MUST be thrown
if a {{BaseAudioContext/[[render quantum size]]}} outside this range
is specified.
</p>

<div class=note>
Note: the upper limit of 6 seconds was chosen to support applications
using the deprecated {{ScriptProcessorNode}} interface at its highest
buffer size of 16384 and the lowest supported sample rate of 3000 Hz.
For a context sample rate of 3000 Hz the supported range is [1,
18000]. Higher sample rates will have a higher upper bound.
</div>

<h3 id="rendering-loop">
Rendering an Audio Graph</h3>

Expand Down