这里记录一下ffmpeg的编译过程并且在Andorid中使用的过程。

编译ffmpeg

这里拿的当前日期最新的release版本ffmpeg4.0.2，编译环境mac，下载mac版本的ffmepg后进行编译，编译脚本build.sh如下：

#!/bin/bash
export NDK=/Users/linchen/Library/Android/sdk/ndk-bundle
export SYSROOT=$NDK/platforms/android-19/arch-arm/
export TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64
export CPU=arm
export PREFIX=/Users/linchen/Desktop/arm #最终编译后的头文件以及so包的位置
export ADDI_CFLAGS="-marm"
function build_one
{
./configure \--prefix=$PREFIX \--cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \--arch=arm \--sysroot=$SYSROOT \--extra-cflags="-Os -fpic $ADDI_CFLAGS" \--extra-ldflags="$ADDI_LDFLAGS" \--cc=$TOOLCHAIN/bin/arm-linux-androideabi-gcc \--nm=$TOOLCHAIN/bin/arm-linux-androideabi-nm \--enable-shared \--enable-runtime-cpudetect \--enable-gpl \--enable-small \--target-os=android \--enable-cross-compile \--disable-debug \--disable-static \--disable-doc \--disable-asm \--disable-ffmpeg \--disable-ffplay \--disable-ffprobe \--enable-postproc \--enable-avdevice \--disable-symver \--disable-stripping \
$ADDITIONAL_CONFIGURE_FLAG
sed -i '' 's/HAVE_LRINT 0/HAVE_LRINT 1/g' config.h
sed -i '' 's/HAVE_LRINTF 0/HAVE_LRINTF 1/g' config.h
sed -i '' 's/HAVE_ROUND 0/HAVE_ROUND 1/g' config.h
sed -i '' 's/HAVE_ROUNDF 0/HAVE_ROUNDF 1/g' config.h
sed -i '' 's/HAVE_TRUNC 0/HAVE_TRUNC 1/g' config.h
sed -i '' 's/HAVE_TRUNCF 0/HAVE_TRUNCF 1/g' config.h
sed -i '' 's/HAVE_CBRT 0/HAVE_CBRT 1/g' config.h
sed -i '' 's/HAVE_RINT 0/HAVE_RINT 1/g' config.h
make clean
# 这里是定义用几个CPU编译
make -j4
make install
}
build_one

build.sh在ffmpeg4.0.2的根目录下，首先需要安装一些需要的编译环境如gcc等，由于我的机子中以前已经安装了，所以直接运行bash build.sh命令就可以了，编译后在我的桌面上会出现arm文件夹：

其中include文件夹是导出的头文件文件夹，lib中的so包是需要使用的，接下来新建一个支持c++的Android项目，在新建的时候选择support c++，Android Studio会自动帮我们配置好，接下添加编译好的文件到Android Studio中：

由于我的手机是arm64-v8a的cpu架构，又由于编译ffmpeg选择的架构，所以这里使用armeabi通用架构支持，因此文件夹就创建了armeabi，如果手机cpu架构不同，可以再编译ffmpeg的时候指定对应的架构，具体参考这篇文章。

接下来编写一下Cmake代码：

cmake_minimum_required(VERSION 3.4.1)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)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)set(distribution_DIR ${CMAKE_SOURCE_DIR}/src/main/jni/armeabi)
add_library( avutilSHAREDIMPORTED )
set_target_properties( avutilPROPERTIES IMPORTED_LOCATION${distribution_DIR}/libavutil.so)
add_library( swresampleSHAREDIMPORTED )
set_target_properties( swresamplePROPERTIES IMPORTED_LOCATION${distribution_DIR}/libswresample.so)
add_library( avcodecSHAREDIMPORTED )
set_target_properties( avcodecPROPERTIES IMPORTED_LOCATION${distribution_DIR}/libavcodec.so)
add_library( avfilterSHAREDIMPORTED )
set_target_properties( avfilterPROPERTIES IMPORTED_LOCATION${distribution_DIR}/libavfilter.so)
add_library( swscaleSHAREDIMPORTED )
set_target_properties( swscalePROPERTIES IMPORTED_LOCATION${distribution_DIR}/libswscale.so)
add_library( avdeviceSHAREDIMPORTED )
set_target_properties( avdevicePROPERTIES IMPORTED_LOCATION${distribution_DIR}/libavdevice.so)
add_library( avformatSHAREDIMPORTED )
set_target_properties( avformatPROPERTIES IMPORTED_LOCATION${distribution_DIR}/libavformat.so)
add_library( postprocSHAREDIMPORTED )
set_target_properties( postprocPROPERTIES IMPORTED_LOCATION${distribution_DIR}/libpostproc.so)
set(CMAKE_VERBOSE_MAKEFILE on)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")
include_directories(src/main/cpp)
include_directories(src/main/jni/include)target_link_libraries( # Specifies the target library.native-libavutil       #工具库(大部分需要)swresample    #音频采样数据格式转换avcodec      #编解码(重要)avfilter      #滤镜特效处理swscale       #视频像素数据格式转换avdevice     #各种设备的输入输出avformat     #封装格式处理postproc     #后加工# Links the target library to the log library# included in the NDK.${log-lib})

然后再MainActivity中使用so库：

public class MainActivity extends AppCompatActivity {// Used to load the 'native-lib' library on application startup.static {//加载so包是有序的一定要那么写，不过这里我是复制过来的，所以没出现问题System.loadLibrary("avutil");System.loadLibrary("swresample");System.loadLibrary("avcodec");System.loadLibrary("avfilter");System.loadLibrary("swscale");System.loadLibrary("avdevice");System.loadLibrary("avformat");System.loadLibrary("postproc");System.loadLibrary("native-lib");}@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);// Example of a call to a native methodTextView tv = (TextView) findViewById(R.id.sample_text);tv.setText(stringFromJNI());}/*** A native method that is implemented by the 'native-lib' native library,* which is packaged with this application.*/public native String stringFromJNI();
}

这里编译过程中遇到一个问题：

Build command failed. Error while executing process /Users/linchen/Library/Android/sdk/cmake/3.6.4111459/bin/cmake with arguments {--

...

../../../../src/main/jni/armeabi/libavutil.so: error adding symbols: File in wrong format clang++: error: linker command failed with exit code 1 (use -v to see invocation) ninja: build stopped: subcommand failed.

问题是jni文件夹下的架构包缺失，使用ndk abi过滤器过滤即可：

ndk {abiFilters 'armeabi'}

编译完成后运行项目发现直接奔溃了，说ffmpeg的so包找不到，解压apk一看还真是，最终发现设置sourceSets的路径不对，修改如下：

sourceSets{main{jniLibs.srcDirs = ['src/main/jni']}}

最终编译成功，项目正常启动，不过还没写代码验证，这里主要先记录一下配置的过程。

项目地址如下：

https://github.com/JerryChan123/FFmpegDemo

参考资料

https://www.jianshu.com/p/da64059799d5

https://www.jianshu.com/p/3b58174e89f1