JMR-devandClaude Opus 5
e84ab6a89d
Conversions now go through WorkManager instead of a viewModelScope coroutine,
so a job outlives the ViewModel, survives process death, and keeps running
when the user leaves the app.
The foreground service type needs three branches across the supported range,
which is why ConversionForegroundType exists rather than a constant:
API 33 no type is required at all
API 34 a type is mandatory, but mediaProcessing does not exist yet, so
dataSync is the only sensible fit
API 35+ mediaProcessing, whose own documentation describes it as
"converting media to different formats"
The manifest declares both types on WorkManager's SystemForegroundService
via tools:node="merge" -- setForeground runs *that* service, not one of
ours, so declaring the type on an app-owned service would have no effect.
The manifest cannot branch on API level, so the runtime picks which type is
actually passed.
Both types share a budget of six hours per twenty-four across the whole app.
When it runs out WorkManager reports STOP_REASON_FOREGROUND_SERVICE_TIMEOUT,
which the worker translates into Result.retry() rather than a failure: the
work is still valid, there is simply no budget right now. The UI surfaces
that as a distinct Waiting state that explains the pause instead of showing
an error.
Expedited work is deliberately not used. It maps to JobScheduler expedited
jobs with a short quota, which is the wrong shape for a multi-minute
transcode.
POST_NOTIFICATIONS is requested when the user taps Convert, not on first
launch, so the ask arrives with visible justification. The conversion starts
either way -- without the permission the foreground service still runs, but
its progress notification is confined to the Task Manager rather than the
shade. Notification updates are throttled to roughly one per second because
progress updates arrive far faster than the system UI can absorb.
Tests run against the real WorkManager rather than a test double,
specifically so setForeground and the declared service type are exercised on
a device that enforces them. Verified on an API 37 emulator: the service
starts, and logcat shows no type or permission exceptions.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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.