之前一直在linux下編譯FFmpeg，最近換電腦了，嘗試了下在mac下編譯ffmpeg,特記錄之。
一. 准備工作
1. 下載FFmpeg。(http://ffmpeg.org/download.html#releases)，看了下最新的是4.1.4，我用的是3.4.6。
2. 下載mac上使用的NDK。(https://developer.android.google.cn/ndk/downloads/index.html), 我用的是android-ndk-r14b-darwin-x86_64.zip，不推薦使用ndk-bundle,有些頭文件在ndk-bundle里沒有，遇到過一次。
3. 修改FFmpeg3.4.6目錄下的configure文件。如果不修改的話之后編譯生成的版本號會加在so的后面，會導致android不能識別，切記。
修改的內容如下，將：
SLIBNAME_WITH_MAJOR='$(SLIBNAME).$(LIBMAJOR)' LIB_INSTALL_EXTRA_CMD='$$(RANLIB)"$(LIBDIR)/$(LIBNAME)"' SLIB_INSTALL_NAME='$(SLIBNAME_WITH_VERSION)' SLIB_INSTALL_LINKS='$(SLIBNAME_WITH_MAJOR)$(SLIBNAME)'
修改成：
SLIBNAME_WITH_MAJOR='$(SLIBPREF)$(FULLNAME)-$(LIBMAJOR)$(SLIBSUF)' LIB_INSTALL_EXTRA_CMD='$$(RANLIB)"$(LIBDIR)/$(LIBNAME)"' SLIB_INSTALL_NAME='$(SLIBNAME_WITH_MAJOR)' SLIB_INSTALL_LINKS='$(SLIBNAME)'
4. 編寫編譯用的腳本文件。這個網上有很多，我找到了兩個可以用的：
用於編譯 armeabi-v7a、arm64-v8a、x86_64版本的：
#!/bin/bash echo "進入FFmpeg編譯腳本" # NDK環境 export NDK=/Users/haiyuegao/Library/Android/android-ndk-r14b export SYSROOT=$NDK/platforms/android-21/arch-arm export TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64 PREFIX=android-build COMMON_OPTIONS="\ --prefix=android/ \ --target-os=android \ --enable-shared \ --enable-runtime-cpudetect \ --enable-small \ --disable-static \ --disable-debug \ --disable-ffmpeg \ --disable-ffplay \ --disable-ffprobe \ --disable-ffserver \ --disable-doc \ --disable-symver \ --disable-asm \ --disable-stripping \ --disable-armv5te \ " function build_android { echo "開始編譯FFmpeg..." # armeabi echo "開始編譯FFmpeg(armeabi)" ./configure \ --libdir=${PREFIX}/libs/armeabi \ --incdir=${PREFIX}/include/armeabi \ --pkgconfigdir=${PREFIX}/pkgconfig/armeabi \ --arch=arm \ --cpu=armv6 \ --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \ --sysroot=$SYSROOT \ --extra-ldexeflags=-pie \ ${COMMON_OPTIONS} make clean make -j8 && make install echo "結束編譯FFmpeg(armeabi)" # armeabi-v7a echo "開始編譯FFmpeg(armeabi-v7a)" ./configure \ --libdir=${PREFIX}/libs/armeabi-v7a \ --incdir=${PREFIX}/include/armeabi-v7a \ --pkgconfigdir=${PREFIX}/pkgconfig/armeabi-v7a \ --arch=arm \ --cpu=armv7-a \ --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \ --sysroot=$SYSROOT \ --extra-cflags="-march=armv7-a -mfloat-abi=softfp -mfpu=neon" \ --extra-ldexeflags=-pie \ ${COMMON_OPTIONS} make clean make -j8 && make install echo "結束編譯FFmpeg(armeabi-v7a)" # arm64-v8a echo "開始編譯FFmpeg(arm64-v8a)" ./configure \ --libdir=${PREFIX}/libs/arm64-v8a \ --incdir=${PREFIX}/include/arm64-v8a \ --pkgconfigdir=${PREFIX}/pkgconfig/arm64-v8a \ --arch=aarch64 \ --cpu=armv8-a \ --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \ --sysroot=$SYSROOT \ --extra-ldexeflags=-pie \ ${COMMON_OPTIONS} make clean make -j8 && make install echo "結束編譯FFmpeg(arm64-v8a)" # x86_64 echo "開始編譯FFmpeg(x86_64)" ./configure \ --libdir=${PREFIX}/libs/x86_64 \ --incdir=${PREFIX}/include/x86_64 \ --pkgconfigdir=${PREFIX}/pkgconfig/x86_64 \ --arch=x86_64 \ --cpu=x86_64 \ --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \ --sysroot=$SYSROOT \ --extra-ldexeflags=-pie \ ${COMMON_OPTIONS} make clean make -j8 && make install echo "結束編譯FFmpeg(x86_64)" echo "編譯結束" }; build_android
用於編譯x86版本的
#!/bin/bash echo "進入FFmpeg編譯腳本" # NDK環境 export NDK=/Users/haiyuegao/Library/Android/android-ndk-r14b export SYSROOT=$NDK/platforms/android-21/arch-x86 export TOOLCHAIN=$NDK/toolchains/x86-4.9/prebuilt/darwin-x86_64 PREFIX=android-build COMMON_OPTIONS="\ --prefix=android/ \ --target-os=android \ --enable-shared \ --enable-runtime-cpudetect \ --enable-small \ --disable-static \ --disable-debug \ --disable-ffmpeg \ --disable-ffplay \ --disable-ffprobe \ --disable-ffserver \ --disable-doc \ --disable-symver \ --disable-asm \ --disable-stripping \ --disable-armv5te \ " function build_android { echo "開始編譯FFmpeg..." # x86 echo "開始編譯FFmpeg(x86)" ./configure \ --libdir=${PREFIX}/libs/x86 \ --incdir=${PREFIX}/include/x86 \ --pkgconfigdir=${PREFIX}/pkgconfig/x86 \ --arch=x86 \ --cpu=i686 \ --cross-prefix=$TOOLCHAIN/bin/i686-linux-android- \ --sysroot=$SYSROOT \ --extra-cflags="-Os -fpic -march=i686 -mtune=intel -mssse3 -mfpmath=sse -m32" \ --extra-ldexeflags=-pie \ ${COMMON_OPTIONS} make clean make -j8 && make install echo "結束編譯FFmpeg(x86)" echo "編譯結束" }; build_android
需要注意的是：要根據自己電腦的實際環境修改下上面的NDK目錄地址，我的NDK地址是：
5. 修改腳本的執行權限。將腳本放置到ffmpeg的根目錄下，為其添加執行權限：
然后打開終端，cd到ffmpeg那級目錄，分別執行以下兩條命令（如果要編譯x86版本，就把shell腳本的名字換成x86版本的那個）：
chmod 777 macos_build_android.sh ./macos_build_android.sh
6. 開始編譯。視電腦的配置不同編譯的時間也不同，我電腦用了大約5分鍾左右完成了編譯。
等待編譯完成，稍后ffmpeg那級目錄會出現一個android-build文件夾，里面包含了我們會用到的庫文件和頭文件。
二. 集成FFmpeg到項目中
1. 新建一個支持C++的Android Studio 項目。
2. 拷貝ffmpeg庫文件和頭文件。將編譯生成的libs文件夾和include文件夾分別拷貝到項目的app目錄下：
3. 更新配置文件。
修改app目錄下的build.gradle文件：
添加下列代碼到gradle文件:
externalNativeBuild { cmake { cppFlags "-std=c++11" } ndk { abiFilters "armeabi-v7a","x86" } } sourceSets { main { jniLibs.srcDirs=['libs'] } }
externalNativeBuild { cmake { path "CMakeLists.txt" } }
最終文件如下：
apply plugin: 'com.android.application' android { compileSdkVersion 28 defaultConfig { applicationId "com.yongdaimi.android.ffapitest" minSdkVersion 19 targetSdkVersion 28 versionCode 1 versionName "1.0" testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner" externalNativeBuild { cmake { cppFlags "-std=c++11" } ndk { abiFilters "armeabi-v7a","x86" } } sourceSets { main { jniLibs.srcDirs=['libs'] } } } buildTypes { release { minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro' } } externalNativeBuild { cmake { path "CMakeLists.txt" } } } dependencies { implementation fileTree(dir: 'libs', include: ['*.jar']) implementation 'com.android.support:appcompat-v7:28.0.0' implementation 'com.android.support.constraint:constraint-layout:1.1.3' testImplementation 'junit:junit:4.12' androidTestImplementation 'com.android.support.test:runner:1.0.2' androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2' }
修改app目錄下的CMakeLists.txt文件：
# For more information about using CMake with Android Studio, read the # documentation: https://d.android.com/studio/projects/add-native-code.html # Sets the minimum version of CMake required to build the native library. cmake_minimum_required(VERSION 3.4.1) # Creates and names a library, sets it as either STATIC # or SHARED, and provides the relative paths to its source code. # You can define multiple libraries, and CMake builds them for you. # Gradle automatically packages shared libraries with your APK. # 添加頭文件路徑 include_directories(${CMAKE_CURRENT_SOURCE_DIR}/include/${ANDROID_ABI}) # 設置FFmpeg庫所在路徑 set(FF ${CMAKE_CURRENT_SOURCE_DIR}/libs/${ANDROID_ABI}) # 打印當前位置信息 message("Current souce file positon: " ${CMAKE_CURRENT_SOURCE_DIR}) # avcodec add_library(avcodec SHARED IMPORTED) set_target_properties(avcodec PROPERTIES IMPORTED_LOCATION ${FF}/libavcodec.so) add_library( # Sets the name of the library. native-lib # Sets the library as a shared library. SHARED # Provides a relative path to your source file(s). src/main/cpp/native-lib.cpp) # Searches for a specified prebuilt library and stores the path as a # variable. Because CMake includes system libraries in the search path by # default, you only need to specify the name of the public NDK library # you want to add. CMake verifies that the library exists before # completing its build. find_library( # Sets the name of the path variable. log-lib # Specifies the name of the NDK library that # you want CMake to locate. log) # Specifies libraries CMake should link to your target library. You # can link multiple libraries, such as libraries you define in this # build script, prebuilt third-party libraries, or system libraries. target_link_libraries( # Specifies the target library. native-lib avcodec # Links the target library to the log library # included in the NDK. ${log-lib})
最終目錄結構如下：
這里一定要注意CMakeLists.txt這個文件的位置，我在Windows下創建AS項目時這個文件在app目錄下，在Mac上創建AS項目時這個文件卻在app/src/main/cpp目錄下，個人為了保持習慣，便將這個文件仍然移動到了app目錄下，若使用Mac上默認的位置，則上述CMakeLists.txt和build.gradle中聲明文件的位置部分也需要修改，切記。
4. 添加測試代碼。打開native-lib.cpp,修改已有的JNI方法：
#include <jni.h> #include <string> extern "C" { #include <libavcodec/avcodec.h> } extern "C" JNIEXPORT jstring JNICALL Java_com_yongdaimi_android_ffapitest_MainActivity_stringFromJNI( JNIEnv *env, jobject /* this */) { std::string hello = "Hello from C++"; hello += avcodec_configuration(); return env->NewStringUTF(hello.c_str()); }
由於FFmpeg是使用純C編寫的，因此在導入其頭文件的時候要注意使用extern "C" 大括號包裹。
之后運行項目，如果能出現相關的配置信息就說明FFmpeg已經加載成功了。
三. 常見錯誤說明
1. Error computing CMake server result.
若編譯出現
Error computing CMake server result. Check for working C compiler: D:/sdk/sdk/ndk-bundle/toolchains/llvm/prebuilt/windows-x86_64/bin/clang.exe Check for working C compiler: D:/sdk/sdk/ndk-bundle/toolchains/llvm/prebuilt/windows-x86_64/bin/clang.exe -- works Detecting C compiler ABI info Detecting C compiler ABI info - done Detecting C compile features Detecting C compile features - done Check for working CXX compiler: D:/sdk/sdk/ndk-bundle/toolchains/llvm/prebuilt/windows-x86_64/bin/clang++.exe Check for working CXX compiler: D:/sdk/sdk/ndk-bundle/toolchains/llvm/prebuilt/windows-x86_64/bin/clang++.exe -- works Detecting CXX compiler ABI info Detecting CXX compiler ABI info - done Detecting CXX compile features Detecting CXX compile features - done Boost version: 1.70.0 Configuring for JNI Configuring done
則打開Build的Toggle View按鈕，根據Log分析出錯的詳細原因，看看是native-lib.cpp的文件找不到或者是其它問題。
2. ninja error needed by missing and no known rule to make it
Error:error: '../../../../src/main/jniLibs/x86/libstblur_preview_api.so',
needed by '../../../../build/intermediates/cmake/debug/obj/x86/libjnistblur_preview_api.so', missing and no known rule to make it
這種錯誤一般是缺失了某個平台的庫導致的，首先查看具體缺失的是哪個平台的so庫，如果該平台的庫不需要，可以在app下的build.gradle中聲明不加載：
ndk { // 聲明只使用這兩個版本的庫,否則默認的可是4個平台 abiFilters 'armeabi-v7a','arm64-v8a' }
或者是檢查下CMakeLists.txt中FFmpeg庫的路徑聲明是否正確：
比如我這里聲明的庫路徑就是app/libs/具體的平台。
參考鏈接：
2. 在Mac中編譯Android平台的FFmpeg（ arm和x86 ）