deepal-player

A homemade video player for the Deepal S09. Plug in a USB stick, pick a file, pick a screen (your own, the passenger seat, or the rear), hit PLAY. The video starts on the chosen screen and you keep a remote on yours: pause, scrub, volume, next episode. Handy when the kids in the back are watching cartoons and you don't want to mash buttons on their display every time.

It is just Jetpack Compose, ExoPlayer (Media3) and libaums for USB. Built around one specific car (Cockpit / HwSAPT, Android 12 underneath), but it should also work on any Huawei head unit from the same family.

How it works

The trick is simple: the app is installed only on the driver's user. To cast video to a different screen we do not spin up a second copy on some other Android user. We launch our own PlayerActivity inside our process via ActivityOptions.launchDisplayId. Android happily lets an Activity start on any display, and the per-user isolation does not get in the way.

   driver (user 13, display 0)              passenger (display 6)
   ┌──────────────────────────┐             ┌──────────────────────┐
   │ MainActivity             │             │                      │
   │  Browser → Scenes → PLAY │             │  PlayerActivity      │
   │  │                       │ launchDisp=6│   ExoPlayer          │
   │  │  remoteTargets        ├────────────▶│   UsbContentProvider │
   │  ▼                       │             │   (reads via token)  │
   │ RemoteControlScreen      │◀── handle ──│                      │
   │  play / pause / seek /   │  registry   │  rear (display 4)    │
   │  next / prev / volume    │             │  PlayerActivity #2   │
   └──────────────────────────┘             └──────────────────────┘

Main pieces:

• MainActivity runs on the driver, owns the USB session and the UsbContentProvider.
• PlayerActivity is launched on the target display inside the same process.
• PlayerRegistry holds a Map<displayId, Handle>. Each PlayerActivity registers in onCreate and MainActivity drives it from its RemoteControlScreen.
• UsbContentProvider serves URIs shaped like content://<authority>/<token>/<idx>/<name>. One token owns the playlist of media files in the current folder. Prev/Next just bumps the index inside the URI, so ExoPlayer correctly reloads the media item.

Stack

• Kotlin 2.0.21 + Compose (with the new K2 plugin).
• AGP 8.7.3 / Gradle 8.14, compileSdk = 35, minSdk = 31.
• Media3 1.7.1.
• io.github.anilbeesetti:nextlib-media3ext:1.7.1-0.9.0. FFmpeg decoders (EAC3, DTS, TrueHD, AC4, Opus, Vorbis, ALAC, FLAC). Without these the audio on a typical WEB-DL or BDRip often does not play because the stock Cockpit mixer does not handle EAC3.
• me.jahnen.libaums:core:0.10.0 plus libusbcommunication:0.3.0 for USB-MSC. If the libusb backend trips on a control-transfer EIO (which happens when the Cockpit vold has already grabbed the device), the app silently falls back to the built-in Android backend (DEVICE_CONNECTION_SYNC).

Build

cd <repo>/deepal-player
export JAVA_HOME="/Applications/Android Studio.app/Contents/jbr/Contents/Home"
echo "sdk.dir=$HOME/Library/Android/sdk" > local.properties
./gradlew :app:assembleRelease
# output: app/build/outputs/apk/release/deepal-player-release.apk

The release build needs app/release.keystore. If you do not have one, generate a self-signed keystore (it is in .gitignore, so it stays local):

keytool -genkeypair -v \
  -keystore app/release.keystore \
  -alias deepal-player -keyalg RSA -keysize 2048 -validity 36500 \
  -storepass <password> -keypass <password> \
  -dname "CN=Deepal Player,O=Private,C=XX"

The build script reads the keystore passwords from ~/.gradle/gradle.properties:

RELEASE_STORE_PASSWORD=<your password>
RELEASE_KEY_PASSWORD=<your password>
RELEASE_KEY_ALIAS=deepal-player

You can also pass them via environment variables with the same names. With nothing set, the release build will fail when it tries to sign the APK.

Things to expect

• USB is single-owner. Only one process on the car can hold the stick at a time. If you also install deepal-player on the passenger user, whoever boots first claims the device. So we only install on the driver and cast to the other screens through launchDisplayId.
• libusb sometimes fails. When Cockpit's vold gets to the device first, libusb returns EIO. The app falls back to the Android backend and that usually works. If it does not, replugging the stick helps.
• Tested on S09 only. Avatr and Aito should work in theory (same HwSAPT base), but the display ids may differ. Not verified.

Wishlist

• R8 / proguard for the release build (currently isMinifyEnabled = false).
• Hook up CarAudioManager from the Huawei Vehicle SDK so the system volume slider shows up.
• A proper multi-user mode: RPC over an abstract socket, so the passenger can browse the stick through a proxy instead of waiting on the driver.