Change #275173

Comments

avcodec/aacenc: rework NMR rate control, pool CPE budgets, add decision memory
Rate control: replace the integral servo with a stateless pressure
offset (exp2(-K*fill/R)) so a drained reservoir cannot wind up and
crater quality after loud stretches; slew-limit the final operating
lambda per frame (bits deviate instead, the reservoir absorbs); seed
the reservoir full at stream start; and track rate strain explicitly:
a long-frame lambda EMA against anchors that scale up when the achieved
distortion/mask ratio flags noise-class content (whose psy masks are
wholesale violated and lambda reads inflated), plus a lambda min-tracker
separating sustained starvation from transient spikes at a comfortable
operating point. The resulting pressure ramp gates every
pressure-adaptive tool from one place.

CPE budget pooling: solve both channels of a pair jointly under one
shared lambda against a pooled budget (NMRSlot defer/solve/commit)
instead of an equal per-channel split, which starved the mid/carrier
while the side gold-plated. Mono and VBR output are unchanged.

Transients: isolated onsets are coded uniformly finer across the short
run and repaid from steady stretches; dense-beat runs get a
starvation-scaled boost; a transition premask clamps START-frame
thresholds toward the previous long frame (an attack cannot mask
backwards).

Decision memory: marginal per-frame re-decisions oscillate audibly, so
every stateful choice now carries hysteresis - band zeroing, PNS
enter/leave with debounce (and near-masked bands staying noise until a
loudness guard), per-grid stereo mode banks that survive window
switches, and the short-TNS accept state.

TNS-covered bands price distortion by the synthesis filter's
re-amplification gain, so the trellis spends where noise will actually
be heard.

Changed files

• libavcodec/aaccoder_nmr.h
• libavcodec/aacenc.h
• tests/ref/fate/id3v2-reenc-delete-metadata
• tests/ref/fate/id3v2-reenc-delete-metadata-keep
• tests/ref/fate/id3v2-reenc-delete-metadata-keep-format
• tests/ref/fate/id3v2-reenc-delete-metadata-keep-stream
• tests/ref/fate/id3v2-reenc-delete-metadata-map-metadata