docs: document AOSP integration steps

README.md

@@ -1,18 +1,94 @@
 ## ViPER4Android FX
 
-Integrate V4A by completing these three steps:
+This repository contains prebuilt ViPER4Android FX artifacts for integration into an AOSP-based ROM build tree.
 
-1.  **Build System:** Add the config to **`device.mk`**:
+It provides:
 
-    ```makefile
-    $(call inherit-product, packages/apps/ViPER4AndroidFX/config.mk)
-    ```
+- `ViPER4AndroidFX`, a presigned prebuilt system app that overrides `AudioFX`.
+- `libv4a_re`, prebuilt 32-bit and 64-bit vendor sound effect libraries installed under `vendor/lib*/soundfx`.
 
-2.  **SELinux Policy:** Add these rules to your **`audioserver.te`** file:
+## Requirements
 
-    ```
-    get_prop(audioserver, vendor_audio_prop) # If Google or MTK device skip line
+- A working AOSP or custom ROM source tree.
+- This repository checked out at `packages/apps/ViPER4AndroidFX`.
+- A product or device makefile where product packages can be inherited, usually `device.mk`.
+- Device SELinux policy sources, including `audioserver.te`.
+- The `libviperaidl` module available elsewhere in the build tree.
 
-    allow audioserver unlabeled:file { read write open getattr };
-    allow hal_audio_default hal_audio_default:process { execmem };
-    ```
+## Integration steps
+
+### 1. Place the package in the source tree
+
+Clone or copy this repository into the Android source tree at:
+
+```text
+packages/apps/ViPER4AndroidFX
+```
+
+The path matters because `config.mk` declares `BUILD_PATH := packages/apps/ViPER4AndroidFX` and adds that path to `PRODUCT_SOONG_NAMESPACES`.
+
+### 2. Inherit the product configuration
+
+Add the package configuration to your device or product makefile, usually `device.mk`:
+
+```makefile
+$(call inherit-product, packages/apps/ViPER4AndroidFX/config.mk)
+```
+
+This adds the following modules to the product:
+
+- `ViPER4AndroidFX`
+- `libv4a_re`
+
+It also adds this directory to `PRODUCT_SOONG_NAMESPACES` and enables `RELAX_USES_LIBRARY_CHECK`.
+
+### 3. Verify the external dependency
+
+`libv4a_re` declares `libviperaidl` as a required module in `Android.bp`.
+
+Before building, confirm that your ROM tree already provides `libviperaidl`. If it does not, add the missing module from the ROM/device source that normally provides ViPER audio support.
+
+### 4. Add SELinux policy
+
+Add the following rules to your device `audioserver.te` policy file:
+
+```te
+get_prop(audioserver, vendor_audio_prop) # If Google or MTK device skip line
+
+allow audioserver unlabeled:file { read write open getattr };
+allow hal_audio_default hal_audio_default:process { execmem };
+```
+
+Depending on your device tree and Android version, these rules may need to be adapted to satisfy existing neverallow rules or vendor policy constraints.
+
+### 5. Build the modules
+
+From the root of the Android source tree, initialize the build environment and select your target:
+
+```sh
+source build/envsetup.sh
+lunch <target>
+```
+
+Then build the package modules directly:
+
+```sh
+mka ViPER4AndroidFX libv4a_re
+```
+
+Alternatively, build your normal ROM target after inheriting `config.mk`.
+
+### 6. Verify install locations
+
+After a successful build, verify that the product output includes:
+
+- `ViPER4AndroidFX.apk` as a system app.
+- `libv4a_re.so` under the vendor sound effects library path for both supported ABIs.
+
+The prebuilt APK is signed with its existing certificate, so the module uses `LOCAL_CERTIFICATE := PRESIGNED`.
+
+## Notes
+
+- This is not a Gradle/Android Studio project and does not build a new APK from source.
+- `ViPER4AndroidFX` overrides `AudioFX` through `LOCAL_OVERRIDES_PACKAGES := AudioFX`.
+- The native effect library is installed as a vendor module using Soong and is built for both 32-bit and 64-bit targets.