short libvpx try

ndk/README.md

@@ -6,7 +6,7 @@ The app loads `libandroidcast_codecs.so` for availability probes and future soft
 
 | Component | Java | Native | Notes |
 |-----------|------|--------|-------|
-| FEC 3/4 + RS | Yes | — | `ProtectionEnvelope`, handshake-safe scopes |
+| 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/` |
@@ -14,7 +14,8 @@ The app loads `libandroidcast_codecs.so` for availability probes and future soft
 ## Enable libvpx (developer)
 
 1. `git submodule update --init third-party/libvpx`
-2. Build `libvpx.a` for your ABI (script stub: `scripts/build-native-codecs.sh`)
+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:
 
 ```bash
@@ -28,4 +29,7 @@ CMake defines `ANDROIDCAST_HAVE_LIBVPX=1` and links the archive when the variabl
 
 - Default: **None** (no FEC/NACK)
 - Enable in **Global settings → Stream protection (UDP)**
-- After handshake, sender and receiver negotiate the effective mode
+- 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](../docs/ROADMAP.md)