Simplify IAMF extension build process

Removed `Android.mk` and `Application.mk`, allowing `CMake` to run directly from the `build.gradle` file. Users no longer need to check out `NDK` or depend on it, simplifying the usage of the IAMF extension.

PiperOrigin-RevId: 684471874

libraries/decoder_iamf/README.md

@@ -1,7 +1,7 @@
 # IAMF decoder module
 
-The IAMF module provides `LibiamfAudioRenderer`, which uses libiamf (the IAMF
+The IAMF module provides `LibiamfAudioRenderer`, which uses the libiamf native
-decoding library) to decode IAMF audio.
+library to decode IAMF audio.
 
 ## License note
 
@@ -17,58 +17,33 @@ To use the module you need to clone this GitHub project and depend on its
 modules locally. Instructions for doing this can be found in the
 [top level README][].
 
-In addition, it's necessary to build the module's native components as follows:
+In addition, it's necessary to fetch libiamf as follows:
 
 * Set the following environment variables:
 
 ```
 cd "<path to project checkout>"
-
 IAMF_MODULE_PATH="$(pwd)/libraries/decoder_iamf/src/main"
 ```
 
-*   Download the [Android NDK][] and set its location in an environment
+* Fetch libiamf:
-    variable. This build configuration has been tested on NDK r27.
 
 ```
-NDK_PATH="<path to Android NDK>"
+cd "${IAMF_MODULE_PATH}/jni" && \
+git clone https://github.com/AOMediaCodec/libiamf.git
 ```
 
-*   Fetch libiamf:
+* [Install CMake][]
 
-Clone the repository containing libiamf to a local folder of choice - preferably
+Having followed these steps, gradle will build the module automatically when run
-outside of the project checkout. Link it to the project's jni folder through
+on the command line or via Android Studio, using [CMake][] and [Ninja][] to
-symlink.
+configure and build libiamf and the module's [JNI wrapper library][].
-
-```
-cd <preferred location for libiamf>
-
-
-git clone https://github.com/AOMediaCodec/libiamf.git libiamf && \
-cd libiamf && \
-LIBIAMF_PATH=$(pwd)
-```
-
-*   Symlink the folder containing libiamf to the project's JNI folder and run
-    the script to convert libiamf code to NDK compatible format:
-
-```
-cd "${IAMF_MODULE_PATH}"/jni && \
-ln -s $LIBIAMF_PATH libiamf && \
-cd libiamf/code &&\
-cmake . && \
-make
-```
-
-* Build the JNI native libraries from the command line:
-
-```
-cd "${IAMF_MODULE_PATH}"/jni && \
-${NDK_PATH}/ndk-build APP_ABI=all -j4
-```
 
 [top level README]: ../../README.md
-[Android NDK]: https://developer.android.com/tools/sdk/ndk/index.html
+[Install CMake]: https://developer.android.com/studio/projects/install-ndk
+[CMake]: https://cmake.org/
+[Ninja]: https://ninja-build.org
+[JNI wrapper library]: src/main/jni/iamf_jni.cc
 
 ## Build instructions (Windows)
 
@@ -77,13 +52,6 @@ be possible to follow the Linux instructions in [Windows PowerShell][].
 
 [Windows PowerShell]: https://docs.microsoft.com/en-us/powershell/scripting/getting-started/getting-started-with-windows-powershell
 
-## Notes
-
-*   Every time there is a change to the libiamf checkout clean and re-build the
-    project.
-*   If you want to use your own version of libiamf, place it in
-    `${IAMF_MODULE_PATH}/jni/libiamf`.
-
 ## Using the module with ExoPlayer
 
 Once you've followed the instructions above to check out, build and depend on

libraries/decoder_iamf/build.gradle

@@ -1,4 +1,4 @@
-// Copyright (C) 2024 The Android Open Source Project
+// Copyright 2024 The Android Open Source Project
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -17,12 +17,32 @@ android {
     namespace 'androidx.media3.decoder.iamf'
 
     sourceSets {
-        main {
-            jniLibs.srcDir 'src/main/libs'
-            jni.srcDirs = [] // Disable the automatic ndk-build call by Android Studio.
-        }
         androidTest.assets.srcDir '../test_data/src/test/assets'
     }
+
+    defaultConfig {
+        externalNativeBuild {
+            cmake {
+                targets "iamfJNI"
+            }
+        }
+    }
+}
+
+// Configure the native build only if libiamf is present to avoid gradle sync
+// failures if libiamf hasn't been built according to the README instructions.
+if (project.file('src/main/jni/libiamf').exists()) {
+    android.externalNativeBuild.cmake {
+        path = 'src/main/jni/CMakeLists.txt'
+        version = '3.21.0+'
+        if (project.hasProperty('externalNativeBuildDir')) {
+            if (!new File(externalNativeBuildDir).isAbsolute()) {
+                ext.externalNativeBuildDir =
+                        new File(rootDir, it.externalNativeBuildDir)
+            }
+            buildStagingDirectory = "${externalNativeBuildDir}/${project.name}"
+        }
+    }
 }
 
 dependencies {

libraries/decoder_iamf/src/main/jni/Android.mk

@@ -1,32 +0,0 @@
-#
-# Copyright (C) 2024 The Android Open Source Project
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      https://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-WORKING_DIR := $(call my-dir)
-include $(CLEAR_VARS)
-
-# build libiamf.a
-LOCAL_PATH := $(WORKING_DIR)
-include libiamf.mk
-
-# build libiamfJNI.so
-include $(CLEAR_VARS)
-LOCAL_PATH := $(WORKING_DIR)
-LOCAL_MODULE := libiamfJNI
-LOCAL_ARM_MODE := arm
-LOCAL_CPP_EXTENSION := .cc
-LOCAL_SRC_FILES := iamf_jni.cc
-LOCAL_LDLIBS := -llog -lz -lm
-LOCAL_STATIC_LIBRARIES := libiamf
-include $(BUILD_SHARED_LIBRARY)

libraries/decoder_iamf/src/main/jni/Application.mk

@@ -1,18 +0,0 @@
-#
-# Copyright (C) 2024 The Android Open Source Project
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      https://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-
-APP_ABI := all
-APP_PLATFORM := android-21

libraries/decoder_iamf/src/main/jni/CMakeLists.txt

@@ -0,0 +1,46 @@
+#
+# Copyright 2024 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+cmake_minimum_required(VERSION 3.21.0 FATAL_ERROR)
+
+# Enable C++11 features.
+set(CMAKE_CXX_STANDARD 11)
+
+# Define project name for your JNI module
+project(libiamfJNI C CXX)
+
+set(libiamf_jni_root "${CMAKE_CURRENT_SOURCE_DIR}")
+
+# Build libiamf.
+add_subdirectory("${libiamf_jni_root}/libiamf/code"
+                 EXCLUDE_FROM_ALL)
+
+# Add the include directory from libiamf.
+include_directories ("${libiamf_jni_root}/libiamf/code/include")
+
+# Build libiamfJNI.
+add_library(iamfJNI
+            SHARED
+            iamf_jni.cc)
+
+# Locate NDK log library.
+find_library(android_log_lib log)
+
+# Link libgav1JNI against used libraries.
+target_link_libraries(iamfJNI
+                      PRIVATE android
+                      PRIVATE iamf
+                      PRIVATE ${android_log_lib})

libraries/decoder_iamf/src/main/jni/libiamf.mk

@@ -1,35 +0,0 @@
-#
-# Copyright (C) 2024 The Android Open Source Project
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      https://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-
-LOCAL_PATH := $(WORKING_DIR)/libiamf
-
-include $(CLEAR_VARS)
-
-LOCAL_MODULE := libiamf
-LOCAL_ARM_MODE := arm
-LOCAL_C_INCLUDES := $(LOCAL_PATH)/code/include \
-                    $(LOCAL_PATH)/code/src/iamf_dec \
-                    $(LOCAL_PATH)/code/src/common \
-                    $(LOCAL_PATH)/code/dep_codecs/include \
-                    $(LOCAL_PATH)/code/dep_external/include
-LOCAL_SRC_FILES := $(shell find $(LOCAL_PATH)/code/src -name "*.c")
-LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/code/include \
-                    $(LOCAL_PATH)/code/src/iamf_dec \
-                    $(LOCAL_PATH)/code/src/common \
-                    $(LOCAL_PATH)/code/dep_codecs/include \
-                    $(LOCAL_PATH)/code/dep_external/include
-
-include $(BUILD_STATIC_LIBRARY)