BuBuTrim

A lightweight Android video trimming app. Pick videos from the local gallery or open them via the system share sheet, select a segment on a visual timeline, and export the clip.

Property	Value
Application ID	rprop.app.video
Min SDK	Android 10 (API 29)
Target SDK	Android 15 (API 35)
Language	Java 21

Features

• Video browser: Loads local videos from MediaStore and displays them in a grid with cover art and duration
• Multiple entry points: In-app picker, system file picker (ACTION_OPEN_DOCUMENT), and share intent from other apps (ACTION_SEND)
• Visual trimming: Video preview, thumbnail timeline, and dual-thumb RangeSeekBar for selecting start/end times
• Duration limits: Minimum 3 seconds, maximum 10 seconds per trim
• Two trim modes:
  • Fast mode (default): -codec copy — stream copy, faster processing
  • Precise mode: -c:v libx264 -c:a aac — re-encode for more accurate cut points, slower
• Export: Trimmed clips are saved to Movies/VideoCut/ via MediaStore
• Gallery actions: Long-press a video to share or delete it

Tech Stack

Category	Technology
Build	Gradle 8.x, Android Gradle Plugin 8.13.2
UI	AndroidX AppCompat, DataBinding, RecyclerView
Images	Glide 5.x
Video processing	FFmpegKit
Thumbnails	MediaMetadataRetriever

Project Structure

VideoCut/
├── build.gradle              # Root build configuration
├── settings.gradle           # Module: cut
├── gradle.properties
├── gradlew / gradlew.bat
└── cut/                      # Main application module
    ├── build.gradle
    ├── libs/                 # Local FFmpegKit AAR/JAR (must be added manually)
    ├── sign.jks              # Debug signing keystore
    └── src/main/
        ├── AndroidManifest.xml
        ├── java/rprop/app/video/
        │   ├── select/       # Video selection screen
        │   ├── trim/         # Trim screen and core views
        │   ├── utils/        # Video utilities (FFmpeg trim, thumbnail generation)
        │   └── widget/       # Custom widgets (RangeSeekBar, etc.)
        └── res/              # Layouts, strings (includes Chinese values-zh)

Requirements

• JDK 21
• Android SDK (compileSdk 36, buildTools 36.1.0)
• Android NDK 29.0.14206865 (required by FFmpegKit native libraries)
• Android Studio (recommended) or command-line Gradle

Dependency Setup

FFmpegKit is included as a local library from cut/libs/:

implementation fileTree(dir: 'libs', include: ['*.aar', '*.jar'])

Place the FFmpegKit AAR/JAR files in cut/libs/ before building. Alternatively, uncomment the following line in cut/build.gradle to use Maven instead:

implementation 'com.arthenica:ffmpeg-kit-min-gpl:6.0-2'

Build & Install

# Windows
gradlew.bat :cut:assembleDebug

# macOS / Linux
./gradlew :cut:assembleDebug

Release build:

gradlew.bat :cut:assembleRelease

APK output is located at cut/build/outputs/apk/. The app ships only arm64-v8a and x86_64 ABIs.

Usage

1. Launch the app and grant video read permissions
2. Tap a video in the grid, or use the top button to pick a file from the system file manager
3. On the trim screen:
   • Drag the left/right thumbs to set the start and end range
   • Scroll the thumbnail timeline horizontally for longer videos
   • Tap the play button to preview the selected segment
4. Tap Finish, confirm start/end times in the dialog, and optionally enable Precise mode
5. Wait for FFmpeg to finish; the exported file is saved to Movies/VideoCut/

Permissions

Permission	Purpose
READ_EXTERNAL_STORAGE	Read local videos on Android 12 and below
READ_MEDIA_VIDEO	Read local videos on Android 13+

Core Flow

VideoSelectActivity          VideoTrimActivity              VideoUtils
       │                            │                           │
       ├─ Load MediaStore videos     ├─ Preview & timeline UI   ├─ generateThumbnailsInBackground()
       ├─ File picker / share   ──►  ├─ RangeSeekBar selection ──► trim() → FFmpegKit
       └─ Open trim screen          └─ Save via MediaStore        └─ Write temp file to cache

Trim Parameters

Constant	Value	Description
MIN_SHOOT_DURATION	3000 ms	Minimum trim duration
MAX_SHOOT_DURATION	10000 ms	Maximum trim duration
MAX_COUNT_RANGE	10	Number of visible thumbnails on the timeline

Output filename format: {originalName}.{startTime}_{endTime}.mp4 (colons in timestamps are replaced with -).

Notes

• Both debug and release builds are signed with cut/sign.jks — for development/testing only
• Release builds enable ProGuard obfuscation (minifyEnabled true)
• Thumbnail generation is paused during trimming to avoid competing with FFmpeg for resources
• Leaving the trim screen calls FFmpegKit.cancel() to abort any in-progress task

License

No open-source license is specified. Confirm usage rights before distributing.