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Add PSNR (Y/U/V) for outbound-rtp #794

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Merged
merged 9 commits into from
Jul 10, 2025
Merged

Add PSNR (Y/U/V) for outbound-rtp #794

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a3f7c6a
Add PSNR (Y/U/V) for outbound-rtp
fippo Jan 23, 2025
cece6f4
record of doubles
fippo Jan 27, 2025
33b4159
make reference informative
fippo Jan 29, 2025
85afc36
statistical analysis, implementation-defined
fippo Mar 3, 2025
7140c3f
move frequency out of the note
fippo Apr 8, 2025
42d593a
move note to metrics from number of measurements
fippo Apr 8, 2025
810d67d
neutral
fippo Apr 10, 2025
2e31240
gate on hw
fippo Apr 21, 2025
18f34e5
Add guidance note
jan-ivar Jul 10, 2025
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36 changes: 36 additions & 0 deletions webrtc-stats.html
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Expand Up @@ -1966,6 +1966,8 @@ <h3>
unsigned long framesEncoded;
unsigned long keyFramesEncoded;
unsigned long long qpSum;
record&lt;DOMString, double&gt; psnrSum;
unsigned long long psnrMeasurements;
double totalEncodeTime;
double totalPacketSendDelay;
RTCQualityLimitationReason qualityLimitationReason;
Expand Down Expand Up @@ -2218,6 +2220,40 @@ <h2>
formats have ways to vary the quantizer value within the frame.
</p>
</dd>
<dt>
<dfn>psnrSum</dfn> of type <span class="idlMemberType">
record&lt;DOMString, double&gt;</span>
</dt>
<dd>
<p>
MUST NOT [= map/exist =] for audio.
The cumulative sum of the PSNR values of frames encoded by this sender.
The record includes values for the "y", "u" and "v" components.
The count of measurements is in {{psnrMeasurements}}.
</p>
<p>
PSNR is defined in [[ISO-29170-1:2017]].
</p>
<p class="note">
PSNR metrics should primarily be used as a basis for statistical analysis rather
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Avoid "should" in non-normative notes. How about

Suggested change
PSNR metrics should primarily be used as a basis for statistical analysis rather
Authors are expected to use PSNR metrics primarily as a basis for statistical analysis rather

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https://w3c.github.io/webrtc-stats/#dom-rtcinboundrtpstreamstats-totalcorruptionprobability -- literally copied from this note, can you explain why it is ok there but not here?

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I missed it in review of #788. It's not a hard rule, but most WG editors I've spoken with agree avoiding lowercase requirement-laden words avoids confusion and improves readability.

Both notes appear to be speaking to authors rather than implementers, which is fine. But the primary audience of specs are implementers, so it might help to clarify when speaking to someone else. Specs have no authority saying authors should or shouldn't do anything. So it seems more accurate to describe the usage the design anticipates, which is how I interpret these notes.

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No, this note documents that implementers (well, the one) do not think authors should be abusing this for per-frame analysis. 810d67d avoids lower-case should.

than be used as an absolute truth on a per-frame basis.
</p>
</dd>
<dt>
<dfn>psnrMeasurements</dfn> of type <span class="idlMemberType">unsigned long long
</span>
</dt>
<dd>
<p>
MUST NOT [= map/exist =] for audio.
The number of times PSNR was measured. The components of {{psnrSum}} are
aggregated with this measurement.
</p>
<p>
The PSNR is defined in [[ISO-29170-1:2017]].
The frequency of PSNR measurements is [=implementation-defined=].
</p>
</dd>
<dt>
<dfn>totalEncodeTime</dfn> of type <span class=
"idlMemberType">double</span>
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5 changes: 5 additions & 0 deletions webrtc-stats.js
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Expand Up @@ -99,6 +99,11 @@ var respecConfig = {
status: "Internet Draft",
publisher: "IETF"
},
"ISO-29170-1:2017": {
title: "Information technology — Advanced image coding and evaluation",
href: "https://www.iso.org/standard/63637.html",
publisher: "ISO",
},
},
postProcess: [
function generateStatsHierarchy(config, doc) {
Expand Down