JMR-devandClaude Opus 5
25f162923c
SafPickerRoundTripTest began failing on gating legs at API 33, 34, 35 and 37 ninety minutes after it landed, on diffs that cannot cause it -- two KDoc comments, a MIME lookup table, a README paragraph. Every failure named the fixture root, so #93 was filed as a root-discovery race. It was not one, and finding out what it was took making the test say something else first. DocumentsUI was fine throughout: its own `ProvidersAccess: Matched roots` names the fixture authority five times inside the sixty seconds the test spent failing. What failed was reading any window at all -- 1095 `Retrieving node with selector` against 1095 `Node not found` on that leg, against 7 and 2 on the green one. So this now asks whether the app's OWN window is readable before it opens a picker, and prints the accessibility window list when it is not. That list named the culprit on the next occurrence: What it could see: com.android.systemui[type=3], android[type=3] No TYPE_APPLICATION window at all, on a device that had just logged `Displayed org.libremediaconverter/.MainActivity`. `android[type=3]` is system_server, and the same logcat says what it was holding, minutes before this class ran: ANR in com.google.android.apps.nexuslauncher Reason: Input dispatching timed out (Application does not have a focused window) Window{4ed8414 u0 Application Not Responding: com.google.android.apps.nexuslauncher} The launcher ANRs on a loaded runner emulator and the dialog it leaves behind never goes away. It is opaque and fullscreen, so AccessibilityWindowManager drops every application window beneath it -- which is how the app can be Displayed and unreadable at once, the contradiction that made this look like a SAF bug for six PRs. Present on both legs examined, API 33 and 34, at the failure timestamp. So the dialog is dismissed, by resource id rather than by localised button text, `aerr_wait` first so the app under it is left alone. Waking the device and rebuilding the UiAutomation connection are kept behind it and are recorded as measured non-causes rather than as fixes. A second PickActivity is not a remedy for this either, and that was measured: the failing leg opened one for the second test, in the same DocumentsUI process, and read as little from it. The whole pick is still retried, but for a smaller and separate claim -- a picker whose lists were built before their data arrived, which #80's node-level re-find cannot reach because it re-acquires a handle inside the one picker. One API 37 run failed a step deeper, on the file rather than the root. That shape has not been reproduced or diagnosed; the reopen covers it because a fresh pick re-walks from Recent, and the KDoc says that rather than claiming more. Two things the retry must not become. It must not tolerate an absent root, or #64's MIME mutation goes vacuous -- so a missing node is reported rather than retried away, and the mutation was re-run: both tests still fail, still with "the system picker never showed BySelector [TEXT='\QLMC R38 fixtures\E']", in 126 s and 127 s against the 1200 s wrapper timeout. And it must not decide the picker has closed by asking the same accessibility window list that is broken -- so the back presses are counted against Activity.hasWindowFocus, which comes from the framework. Each new path was forced on and measured rather than trusted: the injected-failure run showed the reopen recovering, with four OPEN_DOCUMENT starts for two tests; the rebuild was forced unconditionally and the suite stayed green, ruling out a connection that comes back without FLAG_RETRIEVE_INTERACTIVE_WINDOWS; the dialog dismissal was forced with no dialog present, ruling out a blind click breaking a healthy run. Dismissing a real ANR dialog has not been observed, because the fault has never reproduced locally. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
LibreMediaConverter
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: working, unreleased. Both conversion engines, the router, the background job queue and the join flow are implemented and building. The FFmpeg format tests run green on a physical Pixel 10 Pro XL (API 37) and on local emulators at API 33–36, and CI runs the instrumented suite at API 33–36 on every pull request.
Correction (R18 / #27, 2026-08-22): this line used to say the FFmpeg format tests had "been
written but not yet executed on a device" — true when written, false from the first device pass,
and never updated. FFmpegEngineTest's nine format tests were in every run named above and none
of them failed; the runs are recorded under "Verified on real API 37 hardware" in
docs/api-37-emulator-crash.md and "The sweep, run" in
docs/local-emulator.md. API 37 has no CI row — that emulator image is
broken — so it stays a manual Pixel check before each release.
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: H.264/HEVC, resolution and frame-rate changes, rotation, overlays, and audio to AAC. 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.
It writes MP4 and nothing else. media3-muxer ships WebM, Ogg, WAV and AAC muxers too,
but none can be driven by Transformer — they throw from addMetadataEntry, which the muxer
wrapper calls for every metadata entry a real recording carries. It reads far more than it
writes, Matroska included, which is what makes MKV → MP4 a hardware remux.
FFmpeg — the long tail
Everything Media3 structurally cannot do:
- Containers outside MP4/WebM/Ogg/WAV/AAC — MKV, MOV, AVI, FLV, MPEG-TS, WMV/ASF
- 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
- Codecs Media3's muxers decline even on a stream copy — its MP4 muxer carries AAC, Opus, Vorbis and PCM, but neither MP3 nor FLAC
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."
Remuxing
Changing the container without touching the streams. Copying an H.264 track from MKV into MP4 moves the same samples into a different wrapper: it finishes in seconds instead of minutes, costs no quality, and needs no encoder — which is why it stays on the hardware path even on a device that cannot encode the codec in question.
Copy is a codec choice like any other, so it can be mixed: copy the video and re-encode
only the audio, or the reverse. Picking a codec the source already uses is upgraded to a
copy automatically when the container is changing — if container and codec both already
match, the only reason to run the job is to re-encode it, so it does.
A copy is never attempted on a stream whose codec could not be identified. A needless re-encode costs time; a wrong stream copy costs a file that will not play.
Features
| Formats | |
|---|---|
| Video out | MP4, MOV, MKV, WebM, MPEG-TS, AVI, FLV, WMV/ASF |
| Video codecs | H.264, H.265, VP9, or copy the source stream |
| Audio out | MP3, AAC/M4A, FLAC, Opus, WAV, MKA |
| Audio codecs | AAC, Opus, MP3, FLAC, PCM, or copy the source stream |
| Images | GIF, PNG frame sequences |
| Other | Remux without re-encoding; join several files into one |
Presets cover the common combinations in one tap. The Advanced picker exposes the full container × codec matrix — including combinations that cannot work, which it explains and offers alternatives for rather than hiding.
Conversions run as durable background work, so they survive leaving the app and are restored after a restart.
Building
Requires the Android SDK with API 37. Do not pick a JDK — the repo does.
gradle/gradle-daemon-jvm.properties pins the daemon to Java 25 and carries foojay
download URLs per platform, so Gradle finds an installed Java 25 or downloads one on the
first build, whatever JAVA_HOME points at. JAVA_HOME only chooses the launcher, which
Gradle 9.7.1 will run on Java 8 or newer. Everything the build actually compiles is Java 25,
the app's own bytecode included. ./gradlew --version prints the launcher and the daemon
separately, and they routinely differ.
FFmpeg is committed as a prebuilt archive under bin/, so a clone
builds without a cross-compile. That is deliberate: rebuilding it per CI run made test
results ambiguous, because a red build could mean broken code or a build that hiccuped.
See bin/README.md for its provenance and how to regenerate it.
./gradlew :app:assembleDebug # debug APK
./gradlew :app:testDebugUnitTest # JVM tests
./gradlew :app:connectedDebugAndroidTest # device tests, needs a running device
./gradlew :app:assembleRelease # R8-minified release
See tools/ffmpeg/README.md for why the build is
containerised and which flags matter. That recipe remains the authority — the committed
archive is its output, and is also what satisfies the GPL corresponding-source
obligation.
Testing
Unit tests cover the parts that decide correctness without needing hardware: the routing matrix, the container × codec capability matrix, the FFmpeg argument builder, and both stream-copy-versus-re-encode planners. They run against fabricated device profiles, so branches like "this device cannot encode HEVC" are reachable regardless of what the test machine is.
Instrumented tests cover the parts that only a device can prove: real hardware
transcoding, the foreground service type, and each FFmpeg output format asserted against
the produced file rather than the exit code. The remux tests additionally assert which
engine ran — a stream copy produces an identical file either way, so an output-only
assertion cannot tell a hardware transmux from FFmpeg's -c copy.
Privacy
The app has no INTERNET permission, so it cannot open a network connection at all.
Nothing is uploaded, and there is no analytics or advertising. See PRIVACY.md,
which also explains the permissions WorkManager adds automatically.
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.