Change #275175

Comments

avcodec/aacenc_tns: enable short-block TNS via pooled per-group filters
Per-window filters combined with group-shared scalefactors made
short-block TNS produce decoder-synthesized silence: a weak residual in
one sub-window rounds to zero under the group's scalefactor and the
synthesis filter has nothing to re-amplify, audible as 1.5-3 ms
dropouts on beat content. Fit ONE filter per window group instead, on
the concatenated weighted spectra, and require every window in the
group to pass the prediction-gain bar.

Accepts are Schmitt-gated and run-scoped: within a short run the enter
bar is raised and the hold bar lowered (accept flicker was audible as
gravel), while isolated transient frames - where TNS matters most and
cannot flicker - use the base bar.

Changed files

• libavcodec/aacenc_tns.c