JMR-devandClaude Opus 5
c2e6344aad
`publishProgress` posted with `NotificationManager.notify(NOTIFICATION_ID, …)` directly, on the
very id WorkManager owns through `setForeground`, using a notification built `setOngoing(true)`.
Two posters for one id is a race about which of them wrote last, and on a Pixel 10 Pro XL it was
lost on attempt 3 of 12 while cancelling a `BEST`-tier job:
attempt 3: terminal state = CANCELLED
attempt 3: +300ms active=0 id1001=false ongoing=null <- WorkManager tore it down
attempt 3: +700ms active=1 id1001=true ongoing=true <- a progress tick put it back
attempt 3: +5000ms active=1 id1001=true ongoing=true
Still there ten minutes later, with no app process left in the world to withdraw it. The orphan's
record carried `flags=ONGOING_EVENT|ONLY_ALERT_ONCE` and **no `FOREGROUND_SERVICE`**, which is
what identifies the poster rather than merely suggesting one: WorkManager's own post goes out
with that flag and this one did not.
Whether the user could then swipe it away is deliberately not claimed here. An earlier reading
said "cannot dismiss", on the strength of `isClearable()` returning false — but that is false
purely because `FLAG_ONGOING_EVENT` is set, the record carries neither `FOREGROUND_SERVICE` nor
`NO_CLEAR`, and API 34+ lets an ongoing notification with no foreground service behind it be
swiped. The SystemUI test was impossible behind a secure lock screen and was never done. The
resurrection is what is reproduced, and it is what this fixes.
Progress now goes through `setForegroundAsync` — the non-suspending half of the same call
`doWork` already makes, which is the supported way to update a running worker's foreground
notification. That is not merely a different mechanism for the same post: it hands the id back to
its owner, so the notification WorkManager withdraws when the job ends is the same one the last
progress update wrote, and there is nothing left holding a second reference to it.
Two guards, and they are independent on purpose:
- **`isStopped` short-circuits the whole function.** A tick arriving after the stop has nobody
left to report to, so a stopped worker publishes nothing at all — the `setProgressAsync`
included, which WorkManager refuses for finished work anyway.
- **`setForegroundAsync` refuses on its own** for work whose state is already terminal. That
closes the window between the `isStopped` check and the update reaching the task thread,
which a check alone can only narrow.
The `~1/sec` throttle is unchanged, in effect and in reason: FFmpeg's statistics callback and
Media3's progress polling both fire several times a second, and pushing every one of them janks
the system UI. Routing them through WorkManager does not make them cheap, so the interval stays
exactly where it was. It is reordered into an early return rather than a nested `if`, which is
the only difference.
The initial `setForeground(...)` in `doWork` is untouched and stays a suspending call inside the
`try`. That placement is the whole of the previous commit on this file: a denied background
foreground-service start throws there, and `FailureOutcome` turns it into a retry rather than a
terminal failure. Converting it to `setForegroundAsync` for symmetry would have moved that
exception into an unobserved future and undone it silently.
The future `publishProgress` gets is not awaited — it is called from an engine callback, which is
not a coroutine, and a progress update is not worth blocking one for. Both of its failure modes
are benign, so a refusal is logged rather than propagated: dropping it entirely would make the
one that actually happens, a job finishing mid-update, invisible.
`ProgressNotificationTest` drives the real worker with a recording `ForegroundUpdater` — the same
seam `DeniedForegroundStartTest` uses — and asserts on both halves, because either alone passes
against something wrong. The positive half is that the update reached WorkManager on the id it
already holds, carrying `Notification.EXTRA_PROGRESS` of 42; a test that only checked nothing was
posted directly would pass just as well against a `publishProgress` that had been deleted. The
negative half is that Robolectric's notification manager holds nothing at all, asserted over the
whole manager rather than one id, so a renamed constant cannot make it pass by asking about a
notification nobody posts.
All three were red before the change: `one throttled progress update expected expected:<1> but
was:<0>` (nothing had reached WorkManager), `and must resurrect nothing expected:<0> but was:<1>`
(the device's resurrection, on the JVM), and `50 ticks inside one throttle window must not be 0
updates`. Each guard was then removed on its own to check the test that names it bites: without
`isStopped` the stopped worker publishes twice — `a stopped worker must publish nothing
expected:<1> but was:<2>` — and without the throttle fifty ticks become fifty updates.
`ConcatWorker` reports no progress at all and owns id 1002 by itself, so it has none of this and
none of it is added.
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 have been written but not yet executed on a device.
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.