FFmpegKit - FFmpeg 8.1 Full-GPL for Android

Custom build of FFmpegKit based on FFmpeg 8.1 with full GPL libraries and MediaCodec hardware encoding/decoding.

Features

• FFmpeg 8.1 (full-gpl)
• External libraries: x264, x265, lame (mp3lame)
• Android MediaCodec hardware encoding/decoding: h264, hevc
• Critical stability fix: resolved native SIGSEGV crash in JNI layer — fixed global state pollution causing segment fault on repeated ffmpeg_execute() calls
• Target: Android arm64-v8a, API 24+
• Output: AAR package with JNI bridge

Stability Note: This fork fixes a critical segment fault (SIGSEGV) in the native JNI/C layer that occurred when calling ffmpeg_execute() multiple times. The root cause was FFmpeg's original design as a single-run command-line tool — it relies heavily on global variables and static state. When wrapped as a library via JNI, these global states (e.g., array counters like nb_input_files) were not properly reset between executions, leading to crashes, memory leaks, and state pollution. The fix involved properly resetting global array counters in ffmpeg_cleanup() (see fftools_ffmpeg.c). This was a particularly nasty bug to track down due to its location at the Java/Native boundary, and its resolution significantly improves runtime reliability for production use.

Build Scripts

build_ffmpeg_full.sh (run in WSL)

Builds x264, x265, lame, and FFmpeg from source using Android NDK r25b.

bash build_ffmpeg_full.sh

• Set FORCE_FFMPEG=1 to rebuild only FFmpeg (skip x264/x265/lame)
• Output: prebuilt/android-arm64/ffmpeg/lib/*.so

build_aar.sh (run in WSL)

Builds JNI library via ndk-build, copies FFmpeg .so files, packages AAR with Gradle, and strips debug symbols.

bash build_aar.sh

Steps:

1. ndk-build JNI library
2. Copy FFmpeg .so files from prebuilt/ to android/libs/ (after ndk-build to avoid overwriting)
3. Gradle assembleRelease
4. Strip debug symbols from AAR

Output: android/ffmpeg-kit-android-lib/build/outputs/aar/ffmpeg-kit-release.aar

Prerequisites

• WSL with Android NDK r25b at /home/pisces312/android-ndk-r25b
• Windows Gradle (called via cmd.exe /c "gradlew.bat")
• Source code in src/ffmpeg, src/x264, src/x265, src/lame

Documentation

Document	Description
docs/build-plan.md	FFmpeg 6.0→8.1 migration plan
docs/build-log.md	Build environment, scripts, and results
docs/ffmpeg-modifications.md	All changes to FFmpeg source in this fork

Project Structure

ffmpeg-kit/
  build_ffmpeg_full.sh    # Build FFmpeg + dependencies
  build_aar.sh            # Package AAR
  android/                # Android library project
    jni/                  # JNI source (C bridge)
    libs/arm64-v8a/       # FFmpeg .so files (copied by build_aar.sh)
    ffmpeg-kit-android-lib/ # Java wrapper library
  prebuilt/               # Built FFmpeg libraries
  src/                    # Source code (ffmpeg, x264, x265, lame)
  docs/                   # Project documentation