Carrier-or-decode gated the carrier on getDirectPlaybackSupport, which only
exists on API 33, so every older route force-decoded TrueHD - including
routes that bitstreamed it before the carrier existed. The #1863 Fire TV
Stick 4K Max is Fire OS 8 (API 30): its HDMI route advertises raw TrueHD
and IEC 61937 at 8 channels, 2.12.1 passed TrueHD through, and 2.13.0 hands
the same stream to the FFmpeg decoder. The Shield is API 30 as well.
API 29-32 now asks AudioTrack.isDirectPlaybackSupported about the exact
192kHz/7.1 IEC tuple before offering the carrier. It is coarser than the
API 33 probe - it cannot tell bitstream from offload - but an IEC 61937
track is PCM-shaped by definition, so direct support means the route
carries the frames. getMinBufferSize stays as the precondition on every
tier, and a route that still lies fails AudioTrack initialisation, which
the audio recovery path already answers by blocking direct output and
force-decoding in place. Below API 29 nothing can vouch for the tuple, so
the carrier is still not offered and TrueHD decodes as before.
The tier decision is split from the platform probes so it is unit-testable;
each probe is consulted only on the tiers where its API exists.
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