Index of measured findings not yet filed as issues

[mcfnord]

🤖 AI: Over the last few weeks I've built up a backlog of measured findings and candidate improvements against Jamulus that I haven't opened issues for — some because they're design questions rather than clean bugfixes, some because they were waiting on the PR moratorium, and some just to avoid flooding the tracker. Rather than sit on them or dump them all at once, this is an index of what I have, so maintainers can pull whichever ones are worth a proper write-up. Nothing here needs a reply beyond "yes, open an issue for N" (or "no, not interested"). Each line is one command away from a standalone issue with the evidence, harness, and reproduce steps behind it; I'll only expand the ones you name.

None of this is a new PR — it's a menu. If one of these does turn into code later, it goes through the usual contribution process.

JSON-RPC

• Four doc defects where the published table disagrees with the code. countryName is documented as a number but emits a string; getChannelInfo documents a result.id field no revision has ever emitted (the handler's own comment says why); skillLevel is documented twice. Root cause is structural: CI regenerates the docs from the markers, so the markers are never checked against what the code actually emits.
• String parameters are bounded inconsistently across the five methods that take one. privateChatMessage rejects overlong input, setWelcomeMessage silently truncates, and setServerName / broadcastChatMessage are unbounded — a mix of reject / truncate / accept-anything for the same kind of argument.

Auto jitter buffer (all in corrados's #545 territory)

• The hysteresis term has never functioned since it was added in 2011. iCurDecidedResult is assigned only in Init() and passed to DecideWithHysteresis() by value, so the "previous decision" it compares against is a frozen constant for the life of every connection. Confirmed in source and live via telemetry. Caveat worth stating up front: I measured the obvious one-line fix and it slightly worsens latency and oscillation on the path I tested, so my inclination is a documenting comment, not a behaviour change.
• The auto sizer throws away the one distinction that decides which lever helps. It collapses every failure into a single scalar error rate, so it can't tell late-but-complete arrivals (where more depth helps) from independent loss (where depth is wasted). A cheap run-length signal already computable inside CNetBuf::Get separates the two regimes cleanly in my traces. This is a design conversation, not a patch.

Server performance

• The --multithreading pool-size default may be wrong — this is hoffie's own unanswered checkbox on #2446 (open since 2022). On bare metal at realistic client counts, NUM_CORES-1 beats the shipped idealThreadCount(); and idealThreadCount() ignores CPU affinity on Qt5, so taskset doesn't resize the pool. Important caveat: the rule inverts on two-core hosts, so a naive idealThreadCount()-1 would regress them — any change has to floor or stay configurable.
• The mixer inner loop has meaningful headroom via a loop-interchange/vectorization rewrite that measured bit-identical to current output. Honest scoping: it only matters on a busy (tens-of-clients) server and does nothing for a small jam, and it's the largest restructuring in the mix path, so it needs a design nod before any code.

Codec

• The hardcoded OPUS_SET_PACKET_LOSS_PERC(35) is a fixed point on a tradeoff that's now measured on both sides. It costs clean-line quality but buys real robustness under loss and jitter; both halves are quantified across the shipped quality tiers. A loss-adaptive value is the code-change candidate, but whether the clean-line cost is worth trading is a maintainer call.

Already-open issues I've re-verified with a root cause

• #1591 (scrollbar resets on mute toggle) is still live on current main; I've localized it to lblGlobalInfoLabel show/hide reflowing the mixer's QScrollArea.
• #3604 (dedup the client/server "check for update" code) and #2438 (setChannelName written in two places with divergent truncation) both have small, verified refactor scopes ready to implement once the PR moratorium lifts.

If any of these are worth pursuing, name it and I'll open a focused issue with the full evidence. I can also drop any that overlap work already in flight — pointers to the relevant open issues or PRs are welcome.

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🤖 This message was written by AI and reviewed by @mcfnord.

[pljones]

Apart from

The hysteresis term has never functioned since it was added in 2011.

all sound worth having. For that one, it sounds like there's dead code - and that activating it makes Jamulus worse. That argues for removing the code cleanly.

#1591 (scrollbar resets on mute toggle)

would need verifying on all platforms and checking with Qt 6 where we currently build with Qt 5 -- but I expect it still to be an issue.

None sound urgent -- I've tagged this for 4.1.0, though.