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Use Infinity as highWaterMark value instead of having the sizeAlgorithm returning zero #195

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merged 5 commits into from
Jul 27, 2023
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Use Infinity as highWaterMark value instead of having the sizeAlgorithm returning zero #195

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Use Infinity as highWaterMark value instead of having the sizeAlgorit…
youennf Jul 5, 2023
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Add a note telling why backpressure is disabled
youennf Jul 21, 2023
d33668f
Update index.bs
youennf Jul 27, 2023
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youennf Jul 27, 2023
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youennf Jul 27, 2023
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13 changes: 11 additions & 2 deletions index.bs
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Expand Up @@ -89,8 +89,8 @@ At construction of each {{RTCRtpSender}} or {{RTCRtpReceiver}}, run the followin
4. <a dfn for="ReadableStream">Set up</a> [=this=].`[[readable]]`. [=this=].`[[readable]]` is provided frames using the [$readEncodedData$] algorithm given |this| as parameter.
5. Set [=this=].`[[readable]]`.`[[owner]]` to |this|.
6. Initialize [=this=].`[[writable]]` to a new {{WritableStream}}.
7. <a dfn for="WritableStream">Set up</a> [=this=].`[[writable]]` with its [=WritableStream/set up/writeAlgorithm=] set to [$writeEncodedData$] given |this| as parameter and its [=WritableStream/set up/sizeAlgorithm=] to an algorithm that returns <code>0</code>.
<p class="note">Chunk size is set to 0 to explictly disable streams backpressure on the write side.</p>
7. <a dfn for="WritableStream">Set up</a> [=this=].`[[writable]]` with its [=WritableStream/set up/writeAlgorithm=] set to [$writeEncodedData$] given |this| as parameter and its [=WritableStream/set up/highWaterMark=] set to <code>Infinity</code>.
<p class="note">highWaterMark is set to Infinity to explicitly disable backpressure.</p>
8. Set [=this=].`[[writable]]`.`[[owner]]` to |this|.
9. Initialize [=this=].`[[pipeToController]]` to null.
1. Initialize [=this=].`[[lastReceivedFrameCounter]]` to <code>0</code>.
Expand All @@ -101,6 +101,15 @@ At construction of each {{RTCRtpSender}} or {{RTCRtpReceiver}}, run the followin
<!-- FIXME: Use pipeTo algorithm when available. -->
3. Call <a href="https://streams.spec.whatwg.org/#readable-stream-pipe-to">pipeTo</a> with [=this=].`[[readable]]`, [=this=].`[[writable]]`, preventClose equal to true, preventAbort equal to true, preventCancel equal to true and [=this=].`[[pipeToController]]`.signal.

<p class=note>
Streams backpressure can optimize throughput while limiting processing and memory consumption by pausing data production as early as possible in a data pipeline.
This proves useful in contexts where reliability is essential and latency is less of a concern.
On the other hand, WebRTC media pipelines favour low latency over reliability, for instance by allowing to drop frames at various places and by using recovery mechanisms.
Buffering within a transform would add latency without allowing web applications to adapt much.
The User Agent is responsible for doing these adaptations, especially since it controls both ends of the transform.
For those reasons, streams backpressure is disabled in WebRTC encoded transforms.
</p>

### Stream processing ### {#stream-processing}

The <dfn abstract-op>readEncodedData</dfn> algorithm is given a |rtcObject| as parameter. It is defined by running the following steps:
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