chore(quest): abandon he-aac-refusal

doc/bin/cli.md

@@ -90,6 +90,8 @@ moq ... play --delay 500ms          # trade latency for a jittery link
 Decodes H.264, H.265, and AV1 video and Opus, PCM, and AAC-LC audio using
 the platform hardware decoder where available. `--video-name` and
 `--audio-name` pick a rendition.
+HE-AAC signaled only in band (implicit SBR, as over MPEG-TS) plays as its
+half-rate AAC-LC core.
 
 Playback runs on a clock it owns. `--delay` (default 100 ms) is how far it
 trails the live edge, which is both the jitter a late frame may absorb and the

doc/lib/rs/moq-audio.md

@@ -27,6 +27,10 @@ policy. Decoding likewise separates low-level `decode::Config`, PCM
 | `playback` | One output device mixing every track in a call, with click-free volume ramps |
 | `aec` | Acoustic echo cancellation (a port of WebRTC's), so a laptop with no headset doesn't feed itself back |
 
+AAC decoding refuses HE-AAC its config declares. HE-AAC signaled only in band
+(implicit SBR, as over MPEG-TS) goes undetected and plays as its half-rate
+AAC-LC core.
+
 Highlights:
 
 - **`encode::Publication`** advertises the track and opens the microphone only while someone listens. Stop, swap devices, and restart without changing the track subscribers know; read a level meter for the UI.

quest/m1/audio-codecs/README.md

@@ -16,8 +16,10 @@ publisher can produce AAC.
 Platform first, exactly like video: AudioToolbox on macOS and iOS, Media
 Foundation on Windows, MediaCodec on Android, and symphonia (AAC-LC
 mono/stereo) as the software fallback that openh264 is for H.264. Linux has no
-OS audio decoder, so HE-AAC and multichannel AAC stay refused there, stated in
-the docs and rejected at construction. A platform backend claims every catalog
+OS audio decoder, so multichannel AAC stays refused there, stated in the docs
+and rejected at construction. HE-AAC signaled only in band (implicit SBR, as
+over MPEG-TS) plays as its half-rate LC core on symphonia; detecting it needs a
+full element walk, so the docs state it instead of refusing it. A platform backend claims every catalog
 codec its framework opens, so AC-3, E-AC-3, MP3, and FLAC ride along on the
 hosts that have them; each still needs a fixture before the backend advertises
 it.
@@ -41,7 +43,6 @@ its own decode and encode quest so verification stays per host.
 
 ## Quests
 
-- [HE-AAC refusal](/quest/m1/audio-codecs/he-aac-refusal.md) - implicit-SBR HE-AAC over TS is refused instead of half-decoded as the LC core
 - [TS export PCE](/quest/m1/audio-codecs/ts-export-pce.md) - a TS export of a PCE-described AAC track writes channel_config 0 and the PCE instead of a count-derived config
 - [Layout](/quest/m1/audio-codecs/layout.md) - the settled `Layout` carries up to 7.1 through decode, resample, playback, and the FFI
 - [Decode seam](/quest/m1/audio-codecs/decode-backend.md) - `decode::backend` selects a platform decoder before symphonia, mirroring moq-video

quest/m1/audio-codecs/decode-backend.md

@@ -22,8 +22,10 @@ stats and `moq play` surface.
   AAC-LC mono/stereo only; the platform backends that follow advertise what
   their framework opens and has a fixture for.
 - Move today's Opus, PCM, and symphonia code behind the trait without changing
-  behavior; the HE-AAC sniff from [HE-AAC refusal](/quest/m1/audio-codecs/he-aac-refusal.md)
-  lands in the symphonia backend.
+  behavior. Document per host that symphonia plays implicit-SBR HE-AAC as its
+  half-rate LC core: finding the in-band SBR element needs a full Huffman walk
+  of the channel elements, and symphonia detects it internally without
+  exposing or refusing it.
 - A backend's output rate and layout are what it produced, not what the
   catalog said (HE-AAC doubles the rate); `Consumer` already resamples and
   remixes to the requested output, so that stays the seam's contract.