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Gitea #51 ROOT CAUSE: LoopAtWill was mapped to "loop forever", arming 224 of 603 samples as endless OpenAL sources

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SAURON's "coolant flush sound glitched and perma" is one instance of a systemic
defect.  SetupPatch (L4AUDLVL.cpp) decided looping from the SAMPLE flag alone:

    AL_LOOPING = (info.loop != ForceStatic)

That armed every non-ForceStatic sample -- 224 of the 603 authored zones,
including unmistakable one-shots -- as an OpenAL source that never ends on its
own.  Any such sound whose note-off never arrives plays forever.  Measured 1946
LoopAtWill x Transient arming events in one short session.

The sample flag expresses PERMISSION; the SOURCE decides.  Three facts [T1]:

  * the enum's own comments (L4AUDLVL.h:14-19) -- LoopAtWill = "will play once
    OR LOOP AS DESIRED", ForceStatic = "plays only once EVEN IF LOOPED" (a
    veto), LoopAlways = "ramp up and then down";
  * LoopAtWill is enum value 0, i.e. the DEFAULT an unauthored sample receives
    (WTPresets.cpp:37) -- it cannot mean "loop forever";
  * LoopAlways, the real always-loop, is used by ZERO shipped samples.

"As desired" is the source's authored AudioRenderType (Transient=one-shot vs
Sustained=held), streamed from AUDIO*.RES (AUDLVL.cpp:28) and already consulted
by the renderer (L4AUDRND.cpp:567, AUDREND.cpp:184).  SetupPatch now takes it,
threaded from all three L4AudioSource call sites (Direct/Dynamic3D/Static3D).
New rule: LoopAlways->1, ForceStatic->0, LoopAtWill->the source's render type.

MEASURED before changing behaviour (BT_LOOP_AUDIT=1, scratchpad/loopaudit.py):

    LoopAtWill  x Transient -> loop=0  (was 1)   1946 events
    LoopAtWill  x Sustained -> loop=1  unchanged    65 events
    ForceStatic x Transient -> loop=0  unchanged   292 events

The engine loops (EngineAccel07_z0..z2, EngineMotor01, EnginePower01) are all
LoopAtWill/Sustained and PRESERVED -- no regression there.  All 24 reclassified
samples are genuine one-shots: laser charge/fire/explosion/loaded, missile
loading, engine shift, coolant pressure inc/dec.

A/B PROOF (scratchpad/loopab.py, same session both arms, only BT_LOOP_LEGACY
differs), asking the engine's own BT_AUDIO_DUMP what is still playing with
loop=1 long after every release:

    [legacy] EnginePower01, CoolantPresInc03_z2, CoolantPresDcr03_z2
    [fixed]  EnginePower01

The two stuck coolant sources are the reported symptom.  They were eventually
reclaimed when a later trigger reused the source, which is why the bug was
intermittent -- the "perma" case is when nothing else retriggers it.  The fix
removes the mechanism.

BT_LOOP_LEGACY=1 restores the old rule for a field A/B without a rebuild.  The
layers to listen to are the beam sustains: LaserA/CSustain* are authored
LoopAtWill on a TRANSIENT source, so they now end with the sample instead of
looping until note-off.  The render type is T1 authored data; the interpretation
that LoopAtWill defers to it is a strong reading of the enum + defaults rather
than a disassembled statement, and is flagged as such in the KB.

Plausibly bears on #32 (audio cutting in/out late in a match): a stuck looping
source holds its pool slot for the rest of the round.

Rigs: scratchpad/flushsnd.py (flush start/stop pairing), flushsnd2.py (stuck-
source hunt), loopaudit.py (the classification matrix), loopab.py (the A/B).
KB: context/wintesla-port.md audio section, context/decomp-reference.md env
table (BT_LOOP_AUDIT / BT_LOOP_LEGACY / BT_AUDIO_DUMP / BT_AUD_TAIL),
docs/AUDIO_FIDELITY.md F38.  checkctx.py CLEAN.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
arcattack
2026-07-25 13:20:19 -05:00
co-authored by Claude Opus 5
parent f3bdb3b85a
commit d39227ef39
10 changed files with 622 additions and 15 deletions
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docs/AUDIO_FIDELITY.md
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@@ -553,6 +553,70 @@ nothing lost in THIS stream (listens on 1) but Slide/Rest scrape audio elsewhere
---
<a name="f38"></a>
### F38 — `LoopAtWill` was mapped to "loop forever" (Gitea #51) — FIXED 2026-07-25
**Symptom (playtest night 3, SAURON):** "coolant flush sound glitched and perma" — a coolant sound
started and never stopped; a client restart cleared it.
**Defect.** `PatchLevelOfDetail::SetupPatch` (`L4AUDLVL.cpp`) decided looping from the SAMPLE flag
alone: `AL_LOOPING = (info.loop != ForceStatic)`. That armed **224 of the 603 authored samples** as
OpenAL sources that never end on their own — including unmistakable one-shots (laser fire, explosions,
button clicks). Any such sound whose note-off never arrives plays forever. Measured **1946**
`LoopAtWill × Transient` arming events in a single short session.
**Why the sample flag is not the decision** [T1]:
| evidence | source |
|---|---|
| `LoopAtWill` = "will play once **or loop as desired**"; `ForceStatic` = "plays only once **even if looped**" (a veto); `LoopAlways` = "ramp up and then down" | `L4AUDLVL.h:14-19`, the engine's own comments |
| `LoopAtWill` is enum value **0** — the DEFAULT an unauthored sample receives | `WTPresets.cpp:37` (`none.loop = LoopAtWill`) |
| `LoopAlways`, the real always-loop, is used by **zero** shipped samples | `audiopresets.cpp` (0 occurrences) |
So "as desired" is the **source's** authored `AudioRenderType` — `Transient` (one-shot) vs
`Sustained` (held) — streamed from `AUDIO*.RES` (`AUDLVL.cpp:28`) and already consulted by the
renderer (`L4AUDRND.cpp:567`, `AUDREND.cpp:184`).
**Fix.** `SetupPatch` takes the source's render type; the rule becomes `LoopAlways`→1,
`ForceStatic`→0, `LoopAtWill`→`sustained`. Threaded from all three `L4AudioSource` call sites
(Direct/Dynamic3D/Static3D, `L4AUDIO.cpp:966/1314/1875`).
**Measured, not assumed** (`BT_LOOP_AUDIT=1`, `scratchpad/loopaudit.py`):
| sample flag | source type | loop | events |
|---|---|---|---|
| LoopAtWill | Transient | 0 (**was 1**) | 1946 |
| LoopAtWill | Sustained | 1 (unchanged) | 65 |
| ForceStatic | Transient | 0 (unchanged) | 292 |
The engine loops (`EngineAccel07_z0..z2`, `EngineMotor01`, `EnginePower01`) are all
`LoopAtWill / Sustained` and **preserved**. All 24 reclassified samples are genuine one-shots:
laser charge/fire/explosion/loaded, missile loading, engine shift, coolant pressure inc/dec.
**A/B proof** (`scratchpad/loopab.py`, same session both arms, only `BT_LOOP_LEGACY` differs):
```
[legacy] still playing loop=1 after all releases: EnginePower01, CoolantPresInc03_z2, CoolantPresDcr03_z2
[fixed] still playing loop=1 after all releases: EnginePower01
```
The two stuck coolant sources ARE the reported symptom. Note they were eventually reclaimed when a
later trigger reused the source, which is why the bug was intermittent — the "perma" case is when
nothing else retriggers that source. The fix removes the mechanism.
**Residual risk / how to A/B in the field.** `BT_LOOP_LEGACY=1` restores the old rule without a
rebuild. The layers to listen to are the beam sustains: `LaserASustain*` / `LaserCSustain*` are
authored `LoopAtWill` on a **Transient** source, so they now end with the sample rather than looping
until note-off. If a beam sounds short, that is the knob. [The render type is T1 authored data; the
*interpretation* that `LoopAtWill` defers to it is a strong reading of the enum + defaults, not a
disassembled statement — flagged accordingly.]
**Likely bearing on #32** (audio cutting in and out late in a match): a stuck looping source holds
its pool slot for the rest of the round, so eliminating 1946 potential leaks per session should
reduce source-pool starvation.
---
<a name="validations"></a>
## 4. Validations and KB corrections (no fidelity gap)