JMR-devandClaude Opus 5
48f65f0941
The generated scaffold was a Views-based Material 2 shell with no activity,
no Kotlin sources, and a placeholder package. Replace it with the real base
the conversion work builds on.
Build configuration, with three AGP 9 specifics that contradict most
tutorials still in circulation:
- AGP 9 has built-in Kotlin. Applying org.jetbrains.kotlin.android now fails
the build, so the absence of that plugin is deliberate, not an oversight.
- The Compose compiler plugin is still separate and must be applied, pinned
to 2.2.10 to match the kotlin-gradle-plugin AGP 9.3.1 brings transitively.
Pinning it to the newest Kotlin release instead would mismatch.
- android.kotlinOptions {} was removed; jvm configuration moves to a
top-level kotlin { compilerOptions {} }.
Java compatibility goes 11 -> 17 (AGP 9 requires JDK 17), abiFilters
restrict packaging to arm64-v8a and x86_64, and jniLibs packaging is set
uncompressed so the APK zip-aligns native libraries on 16 KB boundaries.
Every dependency version in the catalog was checked to resolve against
Google Maven rather than copied from documentation. Note that KSP has moved
to standalone versioning (2.3.11) and no longer uses the old
<kotlin>-<ksp> scheme; it is catalogued but left unapplied until Room lands.
Set applicationId to dev.jasonmross.mediaconverter. com.example.* is
rejected by the Play Console, and the application ID is permanent once
published, so it has to be right before the first upload. The display name
is just a string resource and stays changeable.
Document the split license posture: source is MIT, but the distributed
binary will be GPL-3.0 because it bundles FFmpeg built with x264/x265.
LICENSES/README.md records why, including that libass is ISC rather than
GPL, so subtitle burn-in is not what forces the GPL choice.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
3.2 KiB
Media Converter
A free and open-source media converter for Android — batch video transcoding and compression, audio extraction and conversion, GIF and frame export, and file merging.
Android 13+ (API 33). Built with Jetpack Compose and Material 3.
Status: early development. The project scaffold and UI shell exist; the conversion pipeline is being built out. Not yet usable.
Licensing at a glance
- Source code: MIT
- Distributed APK: GPL-3.0 — because it bundles FFmpeg built with x264/x265
That split is deliberate, not an oversight. See LICENSES/README.md
for the reasoning and the corresponding-source obligations.
Architecture
Two conversion engines behind an explicit router, because neither one covers the job alone.
AndroidX Media3 Transformer — the hardware path
Handles the common cases: MP4/MOV in and out, H.264/HEVC, resolution and frame-rate changes, rotation, overlays, audio to AAC, and stream-copy transmuxing. Fully hardware accelerated end to end — MediaCodec decodes to a GL surface and MediaCodec re-encodes, so frames never round-trip through the CPU. Roughly 7–8× realtime on 720p.
FFmpeg — the long tail
Everything Media3 structurally cannot do:
- Containers outside MP4/WebM/Ogg/WAV/AAC — MKV, AVI, FLV, MPEG-TS
- MP3 output — Android has no MP3 encoder at any version; this is a platform gap
- GIF and image sequences
- Input codecs with no platform decoder on the device
- CRF and 2-pass rate control, for the quality tier
Quality tiers
The router is surfaced to users as a quality choice rather than hidden:
| Tier | Engine | Rate control | Trade-off |
|---|---|---|---|
| Fast (default) | Media3 / MediaCodec | bitrate-targeted | ~7–8× realtime, low battery cost |
| Best quality | FFmpeg + x264/x265 | CRF or 2-pass | ~realtime or slower, better quality per byte |
A note on "GPU acceleration"
Android has no GPU video codec path. There are three distinct tiers, and conflating them causes a lot of confusion:
- Fixed-function video codec silicon — reached through
MediaCodec. This is what "hardware accelerated" means for encode and decode. It is not the GPU. - GPU shader cores — genuinely used, but only for filters, scaling, and color effects on already-decoded frames, via OpenGL ES. Never for entropy coding.
- CPU — x264, x265, and software decoders.
FFmpeg's -hwaccel is meaningful on Android only as mediacodec, and even then it
targets direct-to-Surface playback rather than file-to-file transcoding. Vulkan Video
exists in FFmpeg 8.0+ but no shipping Android GPU driver exposes it — no VK_KHR_video_*
extension appears in any Android Vulkan Profile tier.
So this app is hardware accelerated via MediaCodec, and GPU accelerated for effects via GL shaders. Both are real; neither is "the GPU decoding video."
Building
Requires JDK 17+ and the Android SDK with API 37.
./gradlew :app:assembleDebug
The FFmpeg native library is built separately from source; that build is not yet wired into this repository.
Contributing
Contributions are welcome. Note that contributions to the source are under MIT, while
the distributed binary remains GPL-3.0 for the reasons described in LICENSES/README.md.