Android emulator mask testing

Camera / Mask Testing: specialization of android-emulator-harness

Read android-emulator-harness first. That base covers KVM, AVD creation, headless boot, app install/launch, Maestro driving, logcat/screenshot assertion, and teardown. This skill changes only what's needed to put a segmentable human in the camera and run GPU segmentation. Everything else (drive with Maestro, assert on logcat + screenshot) is identical to the base.

This skill ships one fixture: fixtures/person-framed.png, a full-body subject pre-positioned for the emulator's camera-feed crop (see override 3). Feed it directly, or swap in your own subject framed the same way.

The three camera-specific overrides (each cost real debugging time)

1. Use a 32-bit x86 system image, NOT the base's x86_64. MediaPipe Tasks Vision ships libmediapipe_tasks_vision_jni.so for arm64-v8a, armeabi-v7a, and x86, not x86_64. On x86_64 it fails with UnsatisfiedLinkError and segmentation silently falls through to the raw frame. API 30 is the highest 32-bit x86 google_apis image. Verify in the APK: unzip -l app.apk | grep mediapipe (expect a lib/x86/… entry).

   yes | "$SDKMGR" "system-images;android-30;google_apis;x86"
   echo no | "$AVDMGR" create avd -n harness_x86 -k "system-images;android-30;google_apis;x86" -d pixel_3 --force
   

2. Boot with -gpu swangle_indirect, NOT the base's swiftshader_indirect. MediaPipe runs through TFLite's GPU delegate, which needs GLES 3.1 compute shaders. Raw SwiftShader is only GLES 3.0 → [GL_INVALID_ENUM] glCreateShader in TensorsToSegmentationCalculator. swangle (ANGLE over SwiftShader-Vulkan) exposes GLES 3.1. Confirm after boot; this is the make-or-break check:

   adb shell dumpsys SurfaceFlinger | grep -m1 "GLES:"   # MUST say "OpenGL ES 3.1 ... ANGLE"
   

3. Feed the framed subject straight into the camera (-camera-back imagefile:). A recent emulator presents a still image as the back camera. Confirm support first ("$EMU" -help-camera-back lists imagefile: / videofile:); upgrade if missing (yes | "$SDKMGR" emulator). Feed the pre-framed image, not a bare cutout: the imagefile-to-sensor path does not present the image 1:1; it crops and shifts, so a subject centered in the source lands off to the right with the head clipped. fixtures/person-framed.png is pre-compensated. The framing that lands the subject centered and fully in frame:

   • Frame: 9:16 portrait (e.g. 1080 x 1920).
   • Subject height: ~0.42 of the frame height (full body, not a close-up).
   • Subject center: x = 0.25 W, y = 0.58 H. The left-quarter x is deliberate; it cancels the sensor path's rightward shift so the subject reads centered on screen.
   • Background: opaque and contrasting (a light neutral gray works); segmentation needs a clean figure/ground split, and the background is what gets replaced.

   These offsets are emulator/AVD/version specific. Calibrate once: feed the image, select no effect to see the raw camera preview, screenshot it, and nudge the subject's x-center until it reads centered before trusting a run. To re-frame for a different crop, recompose from your own transparent subject using the offsets above.

Full launch (base boot + the three overrides)

sg kvm -c "nohup $EMU -avd harness_x86 \
  -no-window -no-audio -no-boot-anim -no-snapshot \
  -gpu swangle_indirect \
  -camera-back imagefile:$PWD/fixtures/person-framed.png \
  -accel on -port 5554 > /tmp/emulator.log 2>&1 &"
# then base boot-wait, then dumpsys SurfaceFlinger GLES check MUST be 3.1/ANGLE

-no-snapshot forces a clean boot so the camera feed takes effect. Pass an absolute path to the imagefile; the example uses $PWD assuming you launch from the skill dir.

Asserting the mask (beyond the base's logcat gate)

Add these to the base's HARD logcat gate (all must be ABSENT): UnsatisfiedLink, GL_INVALID_ENUM, glCreateShader, CalculatorGraph::Run() failed.

Then drive an effect (Maestro: tapOn: "Dark Office") and Read the screenshot. A working mask shows the person kept and the background replaced. Failure modes: unchanged room (segmentation fell through) or person gone (empty mask). For threshold tuning, iterate the app's maskThreshold/hardness controls and re-Read.

What this adds to the base's scope

• CAN now also validate: mask SHAPE + compositing (person carved, bg swapped).
• Still CANNOT: temporal mask quality (flicker/edge stability) from a STATIC image; that needs motion. Use -camera-back videofile:<abs>/subject.mp4 for a full-frame moving subject when you need to test edge stability over time.

Older emulators without imagefile:

Builds whose -help-camera-back lacks imagefile: can still put a subject in view via the virtualscene wall poster. The headless camera pose is not settable (telnet sensor set is ignored; only the gRPC physical model moves it), so move the poster into the camera's fixed view (camera sits near origin looking down −Z): feed your own transparent full-body cutout as -camera-back virtualscene -virtualscene-poster wall=<subject.png> and set geometry in $SDK/emulator/resources/Toren1BD.posters (back it up first; the wall anchor is guaranteed to render). Upgrading the emulator to get imagefile: is simpler; prefer that.

Teardown

adb -s emulator-5554 emu kill
# only if you used the virtualscene fallback and edited resources:
# cp "$SDK/emulator/resources/Toren1BD.posters.bak" "$SDK/emulator/resources/Toren1BD.posters" 2>/dev/null || true