feat: encoder

.claude/skills/build-compilation-dependencies/SKILL.md

@@ -30,6 +30,7 @@ react-native-audio-api/
 │   │       └── CMakeLists.txt          # Actual Android C++ build target
 │   ├── common/cpp/audioapi/            # Shared C++ (used by all platforms)
 │   │   ├── decoding/                   # Decoder factory, backends, SeekDecoderDaemon, AudioDecoding, AudioFileConcatenator
+│   │   ├── encoding/                   # AudioEncoder interface, EncoderCapabilities, OS encoder/remux selector headers
 │   │   ├── libs/                       # Third-party wrappers (FFmpeg, miniaudio, pffft, …)
 │   │   └── external/                   # Prebuilt binaries per platform
 │   │       ├── android/                # .a static libs (Opus, Ogg, Vorbis, OpenSSL)
@@ -291,6 +292,8 @@ For `MockAudioEventHandlerRegistry`, `TestableXxx` pattern, and full CMakeLists
 | `HAVE_ACCELERATE` | Not set | `GCC_PREPROCESSOR_DEFINITIONS` | Not set |
 | `RN_AUDIO_API_TEST` | Not set | Not set | Always set to 1 |
 
+**OS-API selector headers** (`decoding/OSDecoding.h`, `encoding/OSEncoding.h`, `encoding/OSRemux.h`): common code reaches platform implementations through `#if defined(__ANDROID__)` / `#elif defined(__APPLE__) && !defined(RN_AUDIO_API_TEST)` dispatch. The Apple branch must exclude `RN_AUDIO_API_TEST` because desktop test builds run on macOS (where `__APPLE__` is defined) but do not compile the `ios/` sources. Platform glue selected this way lives in `android/src/main/cpp/audioapi/android/` (e.g. `AndroidDecoding`, `AndroidEncoder`, `AndroidRemux`) and `ios/audioapi/ios/core/utils/` (e.g. `IOSDecoding`, `IOSEncoder`, `IOSRemux`) — both picked up automatically by the CMake glob / podspec glob, no build-file edits needed.
+
 ---
 
 ## Common Build Failure Patterns

.claude/skills/post-work-checks/SKILL.md

@@ -119,13 +119,13 @@ yarn test   # from monorepo root — runs test:js + test:cpp
 
 **When**: after any change to C++ files or TypeScript files in `src/`. Prefer this for a quick local test loop covering both TS and C++ logic; run `yarn validate:fast` before opening a PR.
 
-### AudioEvent enum sync check
+### Enum sync check
 
 ```bash
 yarn check-audio-enum-sync
 ```
 
-**When**: only when you modify the `AudioEvent` enum or any file that maps event names across C++/Kotlin/TypeScript. Skip this step if you already ran `validate:fast` (it includes enum sync).
+**When**: when you modify `AudioEvent`, `FileFormat` / `AudioFileProperties::Format`, or other JSI-crossing recorder enums (`FileDirectory`, `BitDepth`, `IOSAudioQuality`). Skip if you already ran `validate:fast` (it includes enum sync).
 
 ---
 

.claude/skills/post-work-checks/maintenance.md

@@ -10,5 +10,5 @@ Review this skill when `pre-push-update` reports changes in:
 | `packages/react-native-audio-api/package.json` scripts | Package-level command changes (including per-language lint/format) |
 | `lefthook.yml` | Pre-commit / commit-msg hook changes |
 | `scripts/validate.sh` | Tier behavior (`--fast` / `--graph` / `--android` / `--ios` / `--full`), skip rules |
-| `scripts/check-audio-enum-sync*` or `packages/react-native-audio-api/scripts/check-audio-events-sync.sh` | Enum sync check details |
+| `scripts/check-audio-enum-sync*` or `packages/react-native-audio-api/scripts/check-*-enum-sync.sh` / `check-enum-sync.sh` | Enum sync check details (AudioEvent + AudioFileProperties) |
 | `.github/workflows/ci.yml`, `tests.yml`, `graph-tests.yml` | What CI covers vs local validation tiers |

.claude/skills/thread-safety-itc/SKILL.md

@@ -149,6 +149,8 @@ See the `utilities` skill for full API.
 
 **Pitfall — file writer / recorder shutdown:** `TaskOffloader::shutdown()` drains the SPSC queue before joining the worker. Call it (or destroy the offloader) only after `isFileOpen_` is cleared so the audio thread stops enqueueing. Otherwise rotated or closed M4A segments lose seconds of buffered audio. Types with a `.slot` member use `slot == size_t max` as the shutdown sentinel.
 
+**Pitfall — the task type cannot be a nested struct.** `TaskOffloader<T>` constrains `T` with `std::default_initializable`. A task struct carrying default member initializers (which the `.slot` sentinel requires) does *not* satisfy that constraint while its enclosing class is still incomplete, so `using Offloader = TaskOffloader<NestedTask, …>;` inside the class fails to compile with "constraints not satisfied". Making the struct `public` does not help — it is not an access problem. Declare the task type at **namespace scope** instead (`PendingFileWrite`, `PendingCallbackFrames`). Dropping the initializers to satisfy the constraint is worse: `T{}` would then produce `slot == 0`, a valid slot index, making the shutdown sentinel indistinguishable from real work.
+
 ---
 
 ## Driver synchronization (layered model)

.github/workflows/ci.yml

@@ -34,7 +34,7 @@ jobs:
   check-audio-enum-sync:
     uses: ./.github/workflows/ci-check.yml
     with:
-      name: Check AudioEvent enum sync
+      name: Check enum sync
       run: yarn check-audio-enum-sync
 
   build-audio-api:

apps/common-app/src/demos/Record/Record.tsx

@@ -20,6 +20,12 @@ import RecordingVisualization from './RecordingVisualization';
 import Status from './Status';
 import { RecordingState } from './types';
 
+const RECORDING_EXTENSION = FileFormat.Wav;
+
+const RECORDING_EXTENSION_NAME_MAP = {
+  [FileFormat.Wav]: 'wav',
+  [FileFormat.M4A]: 'm4a',
+}
 const Record: FC = () => {
   const [state, setState] = useState<RecordingState>(RecordingState.Idle);
   const [hasPermissions, setHasPermissions] = useState<boolean>(false);
@@ -130,7 +136,11 @@ const Record: FC = () => {
       return;
     }
 
-    const outputPath = info.paths[0].replace(/[^/]+$/, 'recording.m4a');
+    const extension = RECORDING_EXTENSION_NAME_MAP[RECORDING_EXTENSION];
+    const outputPath = info.paths[0].replace(
+      /[^/]+$/,
+      `recording.${extension}`
+    );
 
     const finalPath = await concatAudioFiles(info.paths, outputPath);
     const audioBuffer = await audioContext.decodeAudioData(finalPath);
@@ -262,7 +272,7 @@ const Record: FC = () => {
   }, [onPauseRecording, onResumeRecording]);
 
   useEffect(() => {
-    Recorder.enableFileOutput({ rotateIntervalBytes: 1_000_000, format: FileFormat.M4A });
+    Recorder.enableFileOutput({ rotateIntervalBytes: 1_000_000, format: RECORDING_EXTENSION });
 
     return () => {
       stopPlayback();