android_cast/ndk

Native codecs (libvpx, Opus, Speex)

The app loads libandroidcast_codecs.so for availability probes and future software encode/decode paths.

Current status

Component	Java	Native	Notes
FEC 3/4 + RS	Yes	—	v2 per-shard on wire (FecShardWire); v1 monolithic decode still accepted
NACK + retransmit cache	Yes	—	UDP MSG_NACK, combined with FEC when enabled
libvpx VP8/VP9	Stub	Probe only	HW passthrough until ANDROIDCAST_LIBVPX_LIB is linked
Opus / Speex	Stub	Probe only	Submodules under third-party/

Enable libvpx (developer)

1. git submodule update --init third-party/libvpx
2. Build libvpx.a for your ABI: ./scripts/build-native-codecs.sh arm64-v8a
   (If the repo path has spaces, the script uses /tmp/androidcast-libvpx-$USER automatically.)
3. Rebuild the APK with the static library path:

export ANDROIDCAST_LIBVPX_LIB=/path/to/libvpx.a
./gradlew assembleDebug

CMake defines ANDROIDCAST_HAVE_LIBVPX=1 and links the archive when the variable is set.

Stream protection defaults

• Default: None (no FEC/NACK)
• Enable in Global settings → Stream protection (UDP)
• After handshake, sender and receiver negotiate the effective mode (no protocol version bump)
• Until negotiation completes, UDP protection stays off; peers without FEC support ignore protected frames

Full checklist: docs/ROADMAP.md