JMR-devandClaude Opus 5
b86df47c43
`queryFile` started at `var size = 0L` and only moved off it when a provider answered the
`OpenableColumns.SIZE` column, which the platform documents providers *may* omit. So "this file
is empty" and "nobody would tell me how big it is" reached `OutputPublisher.hasSpaceFor` as the
same number, and `hasSpaceFor(0)` is not a space check -- it is "is there 128 MB free", which any
phone with a working camera passes.
The reachable value is not an inference. On a Pixel 10 Pro XL, `contentResolver.query` on a
`file://` URI returns null outright, so the cursor block never runs at all and the default
survives untouched: `queryFile gave displayName='input' sizeBytes=0`. Robolectric reproduces that
exactly -- null query, and a descriptor that reports 4321 bytes for the same file -- which is why
every test here is a JVM test rather than a device one.
`InputQuery` replaces the two copies of `queryFile`, which were byte for byte identical in
`ConversionViewModel` and `JoinViewModel`, so a fix to either would have been a fix to half the
app. It asks for the size twice: what the provider says, and then what the file itself says
through `openFileDescriptor(uri, "r").statSize`. The second needs no cooperation beyond the input
being openable, which a conversion is about to require anyway, and it is what answers the device
case above. Only when both decline is the answer null, and `InputFile.sizeBytes` is `Long?` so
that null cannot be spelled the same way as zero again.
**What an unknown size does was the decision, and it is deliberately not a refusal.**
`OutputPublisher.hasSpaceForUnknownSize()` produces the same number the defect produced by
accident -- with no size to reserve for, the headroom is all there is left to check -- and that is
worth saying plainly rather than dressing up. What changed is that it is now the answer to a
question that was asked. `hasSpaceFor` means "there is room for this many bytes" and nothing else
claims it.
Refusing was the obvious alternative and would have been worse than the bug: it turns "no
provider answered the SIZE column" into "this file cannot be converted", for a user who can do
nothing about either. A fixed floor was the other, and there is no honest number for it -- a
1 GB floor refuses a 10 MB conversion on a device with 500 MB free, which is the same failure in
a costume. `SpaceCheckTest` pins the choice from both sides: an unmeasurable input must not end
the job, and a full disk must still refuse it.
That second half is why the default answers *through* `hasSpaceFor`. `FakeFailures.FullDisk` in
the instrumented suite overrides `hasSpaceFor` and nothing else, so the delegation is the only
reason it still refuses an unknown-size job. Replacing the delegation with a bare `true` leaves
the full-disk test red with `expected:<Failure {error : Not enough free space to convert.}> but
was:<Failure {error : FFmpegKit failed to start on brand: robolectric...}>` -- the job sailed past
the guard and died at the engine instead.
Both workers get the same shape. The size arrives as input `Data`, which has no null, so the
absence of the key *is* the unknown -- `getLong(key, 0L)` was the other half of the conflation.
When it is absent the worker measures the input itself, which it can do because it holds the URI:
that covers a `request(...)` built by hand and work enqueued before the size became optional, and
it costs an ordinary job nothing because it runs only on the fallback. `ConversionWorker.request`
writes neither the `Data` entry nor the `JobTags.sizeBytes` tag for a size nobody knows, since a
tag reading `size-bytes:0` would come back through `Reattachment` as a confident claim that the
user's file is empty -- and `reattach()`'s `?: 0L` is gone for the same reason.
A join's total is `InputQuery.total`, which is null the moment a *single* input cannot be sized.
Summing the ones that answered was the competing reading and is rejected: a lower bound is
indistinguishable from a real total once it reaches the space check, so the guard would reserve
for half the job and pass. Reverting it to `sumOf { it ?: 0L }` records `[1111]` for a two-file
join whose second input nothing can measure.
Work already in the queue keeps the old conflation, and there is no fixing it. The previous
`request()` always wrote `putLong(KEY_SIZE_BYTES, sizeBytes)`, so a job enqueued before this
commit for a file nothing could size carries the key *present* and set to zero -- which reads
back as a declared size of zero and is trusted, exactly as before. Its `lmc.size-bytes:0` tag
reads back the same way, so `reattach()` shows such a card "0 B" rather than "Size unknown".
Nothing can separate that from a genuinely empty file after the fact, and a rule that treated a
declared zero as suspect would only rebuild the conflation facing the other way. WorkManager
keeps finished work for about a week, so this is a bounded window that clears itself; new work
never enters it.
`hasSpaceFor`'s KDoc claimed peak usage was "roughly input + output at once" while the arithmetic
reserved `input + 128 MB`. The arithmetic is what stays and the doc now says why: `bytes` is the
input's size standing in for the output's, generous for the ordinary conversion (which is asked
for precisely because it shrinks its input) and short for a re-encode to a bulkier codec; the
128 MB absorbs that error and the transient double copy while `publish` runs. Reserving
`input + output` outright would refuse jobs that fit. This is a pre-flight check that stops an
obviously impossible job from spending minutes finding out, not a guarantee -- a conversion that
runs out of space anyway still fails through its engine.
The measurement side of that line is untouched on purpose. `StorageManager.getAllocatableBytes`
is a separate entry with its own device evidence and its own `informational += "UsableSpace"` in
the lint block; this commit is about the number going *in*. `hasSpaceFor(bytes: Long)` keeps its
signature and stays open, so nothing overriding it had to change.
The file card says "Size unknown" rather than `0 B`. Handled at the call site rather than inside
`formatBytes`, because a formatter that invented a number would be the defect on screen; the card
already degrades in words for a file nothing could read.
Five of the seven new tests were red before a line of production code moved, with the numbers
they were about: `expected:<4321> but was:<0>` for a picked file, `expected null, but was:<0>` for
one nothing can measure, `expected:<[1111, 2222]> but was:<[0, 0]>` for the join picker, and
`expected:<[4321]> but was:<[0]>` and `expected:<[3333]> but was:<[0]>` for what the two workers
asked the space check. The tests assert on the *question* rather than the verdict, which matters:
one that only checked whether the job ran would have passed against the defect, since the defect
is that the guard is vacuous rather than that it refuses.
The remaining two needed the new call to exist first, so each was proved by mutation instead.
Answering the unknown with `hasSpaceFor(0L)` inline leaves `expected:<[]> but was:<[0]>` in both
workers; refusing it instead leaves `an unknown size must not end the job; got Failure {error :
Not enough free space to convert.}`. Making the worker always measure rather than trust a declared
size leaves `expected:<[9999]> but was:<[4321]>`.
`join()`'s own use of `InputQuery.total` is tested separately from the function, because
`StagingCleanupSupport` already records what that distinction costs: a tool can be provably right
while nothing calls it. `SucceedingWorkerFactory` now keeps the input `Data` of every request that
reaches a worker -- the only place it is legible, since `WorkInfo` hands back a job's tags and its
output and never the `Data` it was built with -- and the test reads the enqueued total off it.
Restoring `inputs.sumOf { it.sizeBytes ?: 0L }` leaves every other test in the change green and
this one red with `a total that could not be worked out must not be enqueued as a number`.
`ConversionViewModelProbeFailureTest` expected `InputFile(INPUT, "input", 0L)` for an authority no
provider serves. It expects `sizeBytes = null` now, which is the behaviour change stated where a
reader will meet it.
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.