A lightweight Android sample demonstrating Jetpack Media3 as the base for a hands-on video editing assistant. This is not a library just comprehensive wrapper on top of media3 that can be copy pasted to your app for a more developer ergonomic way of using media3

• Preset-driven transformations: Quickly size videos for square (1:1), portrait story (9:16), or widescreen (16:9) outputs while applying normalized crop rectangles and rotation.
• Fine-grained controls: Manually specify width/height, rotation degrees, toggle square crop, mute/remove video, or flatten slow-motion content.
• Encoder tuning: Choose a quality preset (LOW/MEDIUM/HIGH) or explicitly set bitrate, I-frame interval, operating rate, and priority via TranscodeOptions.
• Progress reporting: MediaEditProgress mirrors Transformer.ProgressState, giving live updates in the UI so users know when encoding is waiting, available, or finished.
• Gallery export: Transformations save to cacheDir and immediately copy into MediaStore, so the output shows up in the user’s gallery. On Android 9 and below the app requests WRITE_EXTERNAL_STORAGE first.
• In-app preview: The updated Compose screen embeds an ExoPlayer-based preview so you can scrub and play the edited clip without leaving the editor.
• Robust manager: MediaEditManager handles lifecycle, progress polling via Transformer.ProgressHolder, fallback events, cancellation, and optional encoder factory overrides.

• MediaEditModels.kt defines the request/result/option data classes (crop, resize, transcode, progress, fallback, exception).
• MediaEditManager.kt orchestrates Transformer, encoder settings, effects (crop, presentation, rotate), and progress/fallback callbacks.
• MainActivity.kt renders the polished Compose UI: scrollable cards for source/presets/look/encoder, the run button, progress label, gallery save info, and ExoPlayer preview.

./gradlew :app:assembleDebug

./gradlew :app:installDebug

Then launch the app on a device/emulator, pick a video, apply presets or custom settings, tap Run edit, and review the saved URI + preview.

• The preview uses ExoPlayer 2.19.1; deprecation warnings can be addressed later but the player functions today.
• MainActivity keeps the UI state in Compose (remembering presets, inputs, progress) and surfaces errors via a SnackbarHost.