Add native post-processing module for silence removal and pitch-preserving speed adjustment

modules/video-postprocess/README.md

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+# Video Postprocess Module
+
+Native Expo module for post-processing video clips with silence removal and pitch-preserving speed adjustment.
+
+## Features
+
+- **Silence Removal**: Automatically detects and removes silent portions of video clips using audio amplitude analysis
+- **Pitch-Preserving Speed Adjustment**: Speed up or slow down video while maintaining natural audio pitch
+- **Batch Processing**: Process multiple clips at once
+- **Progress Events**: Real-time progress updates during processing
+- **Configurable**: Customize silence threshold, minimum silence duration, and speed factor
+
+## Usage
+
+### Process a Single Clip
+
+```typescript
+import VideoPostprocess from '@/modules/video-postprocess';
+
+const result = await VideoPostprocess.processClip(
+  inputURL,
+  outputURL,
+  {
+    speedFactor: 1.15,        // 1.0-2.0x speed (default: 1.15)
+    silenceThreshold: -40,     // dB (default: -40)
+    minSilenceDuration: 500    // ms (default: 500)
+  }
+);
+```
+
+### Process Multiple Clips
+
+```typescript
+const results = await VideoPostprocess.processClips(
+  [inputURL1, inputURL2, inputURL3],
+  outputDirectory,
+  {
+    speedFactor: 1.2,
+    silenceThreshold: -35,
+    minSilenceDuration: 400
+  }
+);
+```
+
+### Listen to Progress Events
+
+```typescript
+VideoPostprocess.addListener('onProgress', (event) => {
+  console.log(`Progress: ${event.progress * 100}%`);
+  console.log(`Phase: ${event.phase}`);
+});
+```
+
+## Progress Phases
+
+- `analyzing`: Analyzing audio for silence periods
+- `removing_silence`: Removing detected silence from the clip
+- `adjusting_speed`: Applying speed adjustment with pitch preservation
+- `finalizing`: Exporting the final processed video
+
+## Parameters
+
+### PostprocessOptions
+
+- **speedFactor** (optional): Speed multiplier (1.0-2.0)
+  - `1.0` = normal speed
+  - `1.15` = 15% faster (default)
+  - `2.0` = 2x speed
+
+- **silenceThreshold** (optional): Audio threshold in dB for silence detection
+  - Default: `-40` dB
+  - Lower values = more aggressive silence removal
+
+- **minSilenceDuration** (optional): Minimum duration of silence to remove (in milliseconds)
+  - Default: `500` ms
+  - Prevents choppy micro-cuts
+
+## Implementation Details
+
+### Silence Detection
+
+The module uses AVAssetReader to analyze audio samples and detect silence based on RMS (Root Mean Square) amplitude. Silence periods are detected with hysteresis to avoid choppy cuts.
+
+### Speed Adjustment
+
+Speed adjustment is applied using AVFoundation's time scaling capabilities:
+- Video track is time-scaled
+- Audio track is time-scaled while preserving pitch
+- Natural sounding audio at different speeds
+
+### Processing Pipeline
+
+1. **Load asset**: Load the input video file
+2. **Analyze silence**: Process audio to detect silent periods
+3. **Remove silence**: Create composition excluding silent segments
+4. **Apply speed**: Scale time while preserving pitch
+5. **Export**: Save the processed video to output URL
+
+## Platform Support
+
+- ✅ iOS (AVFoundation)
+- ❌ Android (not implemented)
+- ❌ Web (not supported)
+
+## Testing
+
+Run the test suite:
+
+```bash
+cd test/video
+swift RunPostprocessTests.swift
+```
+
+Test files should be placed in the `test/video/` directory and named `recording1.mov`, etc.

modules/video-postprocess/android/src/main/java/expo/modules/videopostprocess/VideoPostprocessModule.kt

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+package expo.modules.videopostprocess
+
+import expo.modules.kotlin.modules.Module
+import expo.modules.kotlin.modules.ModuleDefinition
+
+class VideoPostprocessModule : Module() {
+  override fun definition() = ModuleDefinition {
+    Name("VideoPostprocess")
+
+    Events("onProgress")
+
+    AsyncFunction("processClip") { inputURL: String, outputURL: String, options: Map<String, Any> ->
+      throw UnsupportedOperationException("VideoPostprocess is not yet implemented on Android")
+    }
+
+    AsyncFunction("processClips") { inputURLs: List<String>, outputDir: String, options: Map<String, Any> ->
+      throw UnsupportedOperationException("VideoPostprocess is not yet implemented on Android")
+    }
+  }
+}

modules/video-postprocess/expo-module.config.json

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+{
+  "platforms": ["apple", "android", "web"],
+  "apple": {
+    "modules": ["VideoPostprocessModule"]
+  },
+  "android": {
+    "modules": ["expo.modules.videopostprocess.VideoPostprocessModule"]
+  }
+}

modules/video-postprocess/index.ts

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+// Reexport the native module. On web, it will be resolved to VideoPostprocessModule.web.ts
+// and on native platforms to VideoPostprocessModule.ts
+export { default } from './src/VideoPostprocessModule';
+export * from  './src/VideoPostprocess.types';