Copies the path Kodi uses, and replaces nothing-but-detection with a route that
actually plays (#1804).
Android will not bitstream raw TrueHD on the TV routes measured here. Both
connected boxes report ENCODING_DOLBY_TRUEHD as offload-only while reporting
ENCODING_IEC61937 at 192kHz/7.1 as bitstream-capable. Kodi models exactly that
split: it packs the carrier itself and offers "AudioTrack (IEC)" as the
recommended sink, treating raw TrueHD as a fallback that it still runs at
192kHz. Media3 only ever hands Android raw TrueHD at the stream rate, which on
the reporter's box takes one write and then never advances the playback head.
TrueHdCarrierSink routes TrueHD onto a dedicated delegate and leaves everything
else on the existing processed sink. The split is deliberate rather than
enforcing that the normal processors stay inactive: the carrier is a bit-exact
byte stream shaped like PCM, so a downmix, Sonic pass or silence skip turns it
into full-scale noise at the receiver. A delegate built with an empty
AudioProcessorChain makes that impossible by construction, instead of putting
the guarantee in a different class from the thing it protects.
The carrier delegate keeps OutputConfig at PCM 16-bit so media3's position,
pending-data and release accounting all stay on their mature PCM path — correct
here, because after packing the stream really is a fixed-rate 192kHz 8-channel
carrier. Only the AudioTrack itself is switched, through the builder modifier
upstream applies just before AudioTrack.Builder.build(). That avoids
reimplementing AudioOutput and avoids the encoded frame-domain mismatch in
androidx/media#3329.
Burst timestamps come from the carrier cadence rather than from whichever
access unit closed the frame; anchoring on the closing unit drifts against the
time the sink derives from written frames and reports a discontinuity on nearly
every frame.
Availability is Kodi's test, not media3's: getMinBufferSize for the exact
192kHz/7.1 IEC tuple, plus getDirectPlaybackSupport where it exists to confirm
the route will bitstream rather than quietly decode. Speed changes, downmix,
normalization and 44.1kHz-family streams all decline the carrier and decode.
Verified on a SEI Robotics Box R 4K Plus (Android 14, armeabi-v7a): the carrier
is selected, the AudioTrack is built as IEC61937 at 192kHz/7.1, no audio decoder
is instantiated, zero timestamp discontinuities, and the clock tracks wall time
with no frozen samples. The same box freezes for ten seconds on raw TrueHD.
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