View, record and stream USB cameras from an Android phone.
No root, no ads, no account.
Plug a webcam, endoscope, microscope or HDMI capture adapter into the phone's USB port and HardLine shows the picture. From there it records, takes stills, and serves the camera to the rest of your network as a web page, an RTSP stream, or a push to an RTMP or SRT server.
It talks to the camera itself, through Android's USB host API and libuvc, so it does not depend on the phone having external-camera support and it does not need root.
Cameras
- Any USB Video Class camera. Uncompressed YUY2, UYVY, NV12, NV21, I420 and 8-bit grey, plus MJPEG, H.264 and H.265.
- Isochronous and bulk transfer, so ordinary webcams and bulk-only devices both work.
- The camera's own controls: brightness, contrast, saturation, hue, sharpness, gamma, white balance, gain, exposure, focus, zoom, pan and tilt. HardLine remembers them per camera.
- USB audio from the camera or a separate USB sound device, mixed with the phone's microphone or the phone's own sound if you want.
- The button on the camera takes a picture, starts a recording or shoots a burst. Headset and media keys can do the same.
Recording
- MP4 with H.264, HEVC or AV1 video and AAC sound, encoded by the phone's hardware.
- Files split by length, loop recording inside a storage budget, and a 4 GB split for FAT cards.
- JPEG stills with optional GPS position in the EXIF data.
- Motion detection that starts a recording, sends an e-mail, or uploads the file over FTP.
Streaming
- A built-in web page to watch and control the camera from any browser.
- Motion-JPEG, HTTP-FLV and Ogg/Opus over HTTP, with optional HTTPS.
- An RTSP server with H.264 or HEVC video and AAC sound, for VLC, OBS and network video recorders.
- Live push to RTMP and RTMPS servers, and SRT as caller or listener with optional encryption.
- The web server announces itself on the local network with mDNS. UPnP port mapping is there too, and stays off until you turn it on.
On screen
- Text overlay with time, battery, GPS position, speed or your own text, and an image watermark.
- The phone's own camera or its screen as an inset in the corner of the picture.
- Rotate, mirror, change the aspect ratio, deinterlace, and a side-by-side view for headsets.
- Picture-in-picture, a floating window, and a view on the lock screen.
Download the APK from the latest release and open it on the phone. Android asks once for permission to install from your browser or file manager.
Obtainium can track releases for you. Tap the badge on a phone that has Obtainium installed and it opens with HardLine ready to add:
Or add this repository's address as the app source by hand.
Releases are signed with a certificate whose SHA-256 fingerprint is:
29:55:29:2A:E7:CF:6B:76:8F:AB:58:99:10:F6:EC:77:10:B0:D5:88:70:F4:C2:BE:87:91:A6:A2:3B:E5:47:88
You can check a download with apksigner verify --print-certs HardLine-*.apk.
HardLine needs Android 8.0 or newer and a phone whose USB port works in host mode. Most phones with
USB-C do. The APK carries arm64-v8a and x86_64 code.
- Plug the camera in. A USB-C hub or an OTG adapter works. Use a powered hub for cameras that draw more than the phone supplies.
- Android asks whether HardLine may use the device. Allow it, and tick the box if you want HardLine to open by itself next time.
- The preview starts. The buttons along the bottom record, watch for motion, take a picture, start the web server and start a live push.
With the web server on, the phone shows its addresses and a QR code. These are the ones you will
use most, with PHONE standing for the phone's address:
| What | Address |
|---|---|
| Control page | http://PHONE:8081/ |
| Video for browsers, Motion-JPEG | http://PHONE:8081/video |
| Video with sound, HTTP-FLV | http://PHONE:8081/live.flv |
| Sound only, Ogg/Opus | http://PHONE:8081/audio.opus |
| Still picture | http://PHONE:8081/snapshot.jpg |
| RTSP | rtsp://PHONE:8554/live |
The server asks for a user name and password. HardLine generates the password on first use and shows it on the same sheet as the addresses.
ffplay "rtsp://admin:PASSWORD@PHONE:8554/live"
vlc "http://admin:PASSWORD@PHONE:8081/live.flv"
curl -u admin:PASSWORD -o still.jpg "http://PHONE:8081/snapshot.jpg"HardLine is at version 0.1 and you should expect bugs. So far it has been tested with:
- A virtual UVC camera on the Android 15 emulator, which is how most of the development happened. It covers MJPEG, YUY2 and H.264, isochronous and bulk transfer, USB audio and the camera button.
- One real camera, a 640x480 USB endoscope with the USB ID
349c:8319.
If you try a camera, please open a camera report, whether it worked or not. The device details sheet in the app has everything the report asks for.
You need JDK 17 or newer, the Android SDK, and bash, curl, tar and patch on the path. The
build downloads the NDK, CMake, libusb and libuvc by itself.
git clone https://github.com/JKook-Plus/HardLine.git
cd HardLine
./gradlew assembleDebug # app/build/outputs/apk/debug/
./gradlew testDebugUnitTest # unit testsdocs/BUILDING.md covers release signing, Windows, and what the native dependency script does.
The repository includes a virtual USB camera. It is a small C program that speaks the USB/IP protocol to the emulator's kernel, so Android sees a real UVC device being plugged in and the app runs its normal USB code against it.
scripts/emulator.sh start
scripts/vcam.sh build && scripts/vcam.sh prepare
scripts/vcam.sh attach --audiodocs/TESTING.md has the full walk-through, including the small RTSP, RTMP, SMTP
and FTP test servers in scripts/.
A foreground service owns the camera. Native code built on libusb and libuvc reads frames and hands them to Kotlin. One OpenGL pipeline turns every pixel format into RGBA, draws the overlays once, and renders the result to the screen and straight into the hardware encoders. The muxers and network protocols are plain Kotlin with no native media libraries, which is why the APK is about 3 MB.
docs/ARCHITECTURE.md walks through the packages and the path of a frame.
HardLine has no analytics, no crash reporting and no advertising. It opens network connections only for the things you switch on: the web and RTSP servers, live push, e-mail alerts, FTP upload, and UPnP. It reads the phone's location only while the position overlay, the speed overlay or EXIF position is on.
Bug reports, camera reports and pull requests are welcome. CONTRIBUTING.md says how to set up, what the code style is and what a pull request should contain. Please report security problems privately, as described in SECURITY.md.
HardLine was inspired by USB Camera by ShenYao China, and its feature set follows that app closely. HardLine is a separate project with its own code. It is not affiliated with that app's developer or endorsed by them.
It is built on libusb and libuvc, and uses Apache Commons Net, JavaMail for Android, ZXing, AndroidX and Kotlin. THIRD_PARTY_NOTICES.md lists their licences. The wordmark is set in Barlow Condensed.
Copyright © 2026 the HardLine contributors.
HardLine is free software. You may share and change it under the terms of the GNU General Public License, version 3. If you distribute a changed version, you must publish its source under the same licence. HardLine comes with no warranty.