atracdenc/src/transient_detector.cpp, branch new_psy_cont

atrac3: add boundary transient thresholding to prune low-value gain transitions

2026-04-06T21:14:19Z

Problem Gain curve generation emitted many +/-1 level transitions that do not correspond to strong local transients. These points consume gain-info bits and can create low-level modulation artifacts without improving transient handling. Solution Introduce explicit transient evidence gating at transition boundaries in CalcCurve(), and wire it to the existing dynamic min-score path. What changed - Added BoundaryTransientScore(env, loc, win): - computes local ratio around each subframe boundary - R = max(max_right/max_left, max_left/max_right) - short symmetric window (win=3 subframes) - Re-enabled minScore usage in CalcCurve() (previously ignored). - For each level transition candidate at loc=sf+1: - keep unconditionally if loc==targetSf (tail neutral anchor) - keep unconditionally if |deltaLevel| >= 2 (strong step) - otherwise keep only if BoundaryTransientScore(loc) >= minScore - Added YAML telemetry: - transient_min_score - transient_window - transition_pruned {loc, delta, score} Why this is safe - Strong transitions are preserved. - Rightmost transition is preserved to keep proper return-to-neutral anchoring. - Only low-confidence small toggles are removed. Measured impact (current branch comparison) Baseline: ea4d33b38 (before this change) Tracks: show_me_your_spine.wav, 13.wav Gain-info bits / points: - spine: 191,697 -> 150,297 bits (delta -41,400; -21.6%) 15,593 -> 10,993 points (delta -4,600) - 13.wav: 1,299,035 -> 979,931 bits (delta -319,104; -24.6%) 97,035 -> 61,579 points (delta -35,456) Subjective note User listening reports improved sound and fixes for some low-level artifacts.

atrac3: make sticky gain quantization conditional and tune thresholds

2026-04-06T18:57:40Z

Problem The distribution-aware sticky quantizer reduced gain-curve bitrate, but in some release/transient frames it over-merged nearby transitions. On spine around 17.657s (ch1/band2), this collapsed the curve shape and could produce an audible spike. What changed - Added frame-level sticky eligibility gating in CalcCurve(). - Sticky is now enabled only when both conditions hold: - intra-frame ratio is limited: max_gain / target <= kStickyMaxIntraFrameRatio - inter-frame target jump is limited: prev_target / target (symmetric) <= kStickyMaxInterFrameRatio - Added local uncertainty guard for sticky hold: - require idx span from [subframeLow, subframeHigh] quantization to be narrow (idxSpan <= 1) before allowing prev-level hold. - Added YAML diagnostics per band/frame to make gating decisions auditable: - sticky_frame_eligible - sticky_intra_ratio - sticky_inter_ratio Threshold tuning Swept candidate pairs on both tracks: - show_me_your_spine.wav - 13.wav Pairs tested: (5,6), (5,8), (6,8), (6,10), (7,8), (7,10), (8,12) Selected: - kStickyMaxIntraFrameRatio = 7.0 - kStickyMaxInterFrameRatio = 10.0 Reason for selection - Keeps safety behavior on known failure site: frame 760, ch1, band2 remains sticky_frame_eligible=false and retains non-collapsed curve shape (loc 1,2,5,7). - Improves gain-modulation bitrate vs previous 6/8 tuning while avoiding fully open behavior. Measured gain-modulation bits (spine + 13.wav) - 6/8: 1,493,639 bits - 7/10: 1,490,732 bits (selected, -2,907 bits vs 6/8) - 8/12: 1,488,824 bits (lowest in sweep; not selected to keep extra margin)

atrac3: add distribution-aware sticky gain quantization

2026-04-06T17:16:00Z

Problem Gain curve construction still produced many +/-1 level toggles across long runs (e.g. 7<->8 chatter). These transitions are usually quantization noise from subframe-level RMS rounding, not real envelope changes, and they consume gain bit budget without improving transient protection. Feature Introduce distribution-aware sticky quantization for subframe gain levels. Instead of quantizing only the subframe centre estimate, we also track a robust within-subframe range and suppress one-step toggles when the previous level is still consistent with that range. Implementation 1) AnalyzeGain now optionally returns per-subframe low/high energy estimates (robust inter-quantile bounds from micro-chunk analysis inside each subframe). 2) CalcCurve now accepts optional subframe low/high vectors. 3) During sfLevel quantization: - compute centre level via RelationToIdx(filtered/target) - if new level differs from previous by exactly 1, and previous level is still inside [idx(low), idx(high)], keep previous level (sticky hold) 4) CreateSubbandInfo wires the new AnalyzeGain outputs into CalcCurve. 5) Existing point0 guard/boundary logic remains intact; this feature operates earlier at sfLevel formation. Why this is safe - Only suppresses +/-1 oscillation when previous level is still supported by observed subframe distribution. - Does not clamp large transitions or remove structurally important points. - Keeps curve scan/priority flow unchanged after sfLevel is formed. Measured impact on current HEAD (gain-info bits) Bit accounting uses ATRAC3 gain syntax: per channel header + per band point-count fields + 9 bits per gain point. show_me_your_spine.wav: - base: 219,552 bits (18,688 points) - with sticky: 172,158 bits (13,422 points) - saved: 47,394 bits, 5,266 points (-21.59% gain-info bits) 13.wav: - base: 1,537,724 bits (123,556 points) - with sticky: 1,146,746 bits (80,114 points) - saved: 390,978 bits, 43,442 points (-25.43% gain-info bits)

atrac3: allow to configure median filter during gain curve calculation

2026-04-05T18:01:46Z

atrac3: Prefer largest locations of gain curve points.

2026-04-05T08:23:54Z

atrac3: use in.back() as staircase target instead of nextLevel

2026-04-05T07:19:40Z

For non-plateau frames, nextLevel (first lookahead subframe of the next frame) can be 6× higher than in.back() on release frames. Using it as the staircase target caused tail subframes to appear below target → spurious amplifying points (e.g. {level:7, loc:31}) on release tails, and underestimated ATT on the peak (33× ratio reduced to 5× because the wrong target inflated the denominator). Fix: always use in.back() (actual last subframe of the analysis window) as the staircase target. That is where the signal truly returns to within this frame. Co-Authored-By: Claude Sonnet 4.6

atrac3: replace CalcCurve with staircase level-scan algorithm

2026-04-05T07:19:26Z

Replaces the monotone-triplet transient detector with a level-based staircase scan that builds the gain curve from the target subframe leftward. The new algorithm correctly handles rising transients by attenuating the loud peak region rather than the quiet onset. Key changes: - 3-point median filter on gain[] suppresses isolated spikes - Per-sf level = RelationToIdx(filtered[sf] / target) - Scan leftward from first-neutral-sf, emit one point per level change - Priority trim: keep up to 6 points with largest |ΔLevel| first Co-Authored-By: Claude Sonnet 4.6

atrac3: fix gc_scale at loc=0 using prev_target/target ratio

2026-03-29T20:00:41Z

When the first detected transient is at location 0, the CalcCurve loop computed level = RelationToIdx(in[0]/target). But in[0] is the ramp START — for loc=0 there is no pre-ramp region, so in[0] is not the right amplitude reference for gc_scale, which divides ALL of bufCur (the previous frame's MDCT window). The external point0 block derives its formula as: hpfRmsNextMod = mean(gain[0..loc-1]) / GainLevel[pts[0].Level] ≈ target point0Level = RelationToIdx(prevTarget / hpfRmsNextMod) ≈ prevTarget/target For loc=0, hpfRmsNextModValid is false and the block cannot fire. Override curve[0].Level inside CalcCurve with RelationToIdx(savedPrevTarget/target) — consistent with the loc>0 formula and correctly bridges cross-frame amplitude. Co-Authored-By: Claude Sonnet 4.6

atrac3: point0 in HPF domain using prevTarget/hpfRmsNextMod; enable band 2

2026-03-29T19:12:00Z

Point0 calculation switched from raw-PCM RMS ratio to HPF-filtered domain: - prevTarget (stored as ctx.LastTarget from previous CalcCurve call) replaces rmsCur - hpfRmsNextMod = mean(gain[0..loc-1]) / GainLevel[pts[0].Level] replaces rmsNextMod (only the pre-ramp constant-level zone, same domain as gain[]) - TCurveBuilderCtx gains LastTarget field; CalcCurve stores target before returning Also extends gain control to band 2 (~11–16 kHz) by changing the skip threshold from band >= 2 to band >= 3. Perceptually sounds better; regression metrics worsen due to broadband measurement not capturing per-band HF improvement. Co-Authored-By: Claude Sonnet 4.6

atrac3: log plateau result and target source inside CalcCurve

2026-03-26T14:13:28Z

Pass yamlLog into CalcCurve so plateau_level, plateau_max_raw, plateau_release, and target/source are emitted directly from the function that computes them, instead of via stale TCurveBuilderCtx fields. Remove LastTarget and LastTargetFromPlateau from the context struct entirely. Co-Authored-By: Claude Sonnet 4.6