FFmpeg: mac下手动编译android上使用的FFmpeg(支持x86、armeabi-v7a、arm64-v8a）

之前一直在linux下编译FFmpeg，最近换电脑了，尝试了下在mac下编译ffmpeg,特记录之。

一. 准备工作

1. 下载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. 下载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，不推荐使用ndk-bundle,有些头文件在ndk-bundle里没有，遇到过一次。

3. 修改FFmpeg3.4.6目录下的configure文件。如果不修改的话之后编译生成的版本号会加在so的后面，会导致android不能识别，切记。

修改的内容如下，将：

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. 编写编译用的脚本文件。这个网上有很多，我找到了两个可以用的：

用于编译 armeabi-v7a、arm64-v8a、x86_64版本的：

#!/bin/bash

echo "进入FFmpeg编译脚本"

# NDK环境    
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 "开始编译FFmpeg..."

    # armeabi
    echo "开始编译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 "结束编译FFmpeg(armeabi)"

    # armeabi-v7a
    echo "开始编译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 "结束编译FFmpeg(armeabi-v7a)"

    # arm64-v8a
    echo "开始编译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 "结束编译FFmpeg(arm64-v8a)"

    # x86_64
    echo "开始编译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 "结束编译FFmpeg(x86_64)"

    echo "编译结束"

};
build_android

用于编译x86版本的

#!/bin/bash

echo "进入FFmpeg编译脚本"

# NDK环境    
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 "开始编译FFmpeg..."

    # x86
    echo "开始编译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 "结束编译FFmpeg(x86)"


    echo "编译结束"

};
build_android

需要注意的是：要根据自己电脑的实际环境修改下上面的NDK目录地址，我的NDK地址是：

5. 修改脚本的执行权限。将脚本放置到ffmpeg的根目录下，为其添加执行权限：

然后打开终端，cd到ffmpeg那级目录，分别执行以下两条命令（如果要编译x86版本，就把shell脚本的名字换成x86版本的那个）：

chmod 777 macos_build_android.sh 
./macos_build_android.sh

6. 开始编译。视电脑的配置不同编译的时间也不同，我电脑用了大约5分钟左右完成了编译。

等待编译完成，稍后ffmpeg那级目录会出现一个android-build文件夹，里面包含了我们会用到的库文件和头文件。

二. 集成FFmpeg到项目中

1. 新建一个支持C++的Android Studio 项目。

2. 拷贝ffmpeg库文件和头文件。将编译生成的libs文件夹和include文件夹分别拷贝到项目的app目录下：

3. 更新配置文件。

修改app目录下的build.gradle文件：

添加下列代码到gradle文件:

　　　　externalNativeBuild {
            cmake {
                cppFlags "-std=c++11"
            }
            ndk {
                abiFilters "armeabi-v7a","x86"
            }
        }
        sourceSets {
            main {
                jniLibs.srcDirs=['libs']
            }
        }

externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }

最终文件如下：

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目录下的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.


# 添加头文件路径
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/include/${ANDROID_ABI})


# 设置FFmpeg库所在路径
set(FF ${CMAKE_CURRENT_SOURCE_DIR}/libs/${ANDROID_ABI})

# 打印当前位置信息
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})

最终目录结构如下：

这里一定要注意CMakeLists.txt这个文件的位置，我在Windows下创建AS项目时这个文件在app目录下，在Mac上创建AS项目时这个文件却在app/src/main/cpp目录下，个人为了保持习惯，便将这个文件仍然移动到了app目录下，若使用Mac上默认的位置，则上述CMakeLists.txt和build.gradle中声明文件的位置部分也需要修改，切记。

4. 添加测试代码。打开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());
} 

由于FFmpeg是使用纯C编写的，因此在导入其头文件的时候要注意使用extern "C" 大括号包裹。

之后运行项目，如果能出现相关的配置信息就说明FFmpeg已经加载成功了。

三. 常见错误说明

1. Error computing CMake server result.

若编译出现

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

则打开Build的Toggle View按钮，根据Log分析出错的详细原因，看看是native-lib.cpp的文件找不到或者是其它问题。

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

这种错误一般是缺失了某个平台的库导致的，首先查看具体缺失的是哪个平台的so库，如果该平台的库不需要，可以在app下的build.gradle中声明不加载：

　　　　　ndk {
            // 声明只使用这两个版本的库,否则默认的可是4个平台
            abiFilters 'armeabi-v7a','arm64-v8a'
        }

或者是检查下CMakeLists.txt中FFmpeg库的路径声明是否正确：

比如我这里声明的库路径就是app/libs/具体的平台。

参考链接：

1.  FFmpeg编译For Android（Mac）

2. 在Mac中编译Android平台的FFmpeg（ arm和x86 ）