Andriod项目导入FFMPEG动态库

上一篇文章介绍了如何在Mac平台下编译FFMPEG，这篇主要介绍如何将编译后的so文件导入Android项目中，

项目文件目录结构

WX20190619-162908.png
- src/main/cpp/include包下的文件可以从FFMPEG编译后的任意CPU架构目录下直接拷贝到cpp目录下即可
- src/main/jniLibs/包下的文件可以从FFMPEG编译后的对应的CPU架构Lib包下拷贝，只需要拷贝以带版本号的so文件即可，如：libavcodec-57.so
  
  WX20190619-163538@2x.png

配置项目的build.gradle文件

android {
  .....
    
    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }
  
    sourceSets{
        main{
            jniLibs.srcDirs = ["src/main/jniLibs"]
        }
    }
}

配置CMakeLists.txt文件

# Cmake版本号
cmake_minimum_required(VERSION 3.4.1)
#项目自动生成的代码
add_library(
        native-lib
        SHARED
        src/main/cpp/native-lib.cpp)

#复用NDK中一些基础的库，如输出log等
find_library(
        log-lib
        log)

#导入FFMPEG动态库：

#1.导入FFMEPG头文件夹路径
include_directories(src/main/cpp/include)
#2. 添加动态库: 库名 SHARED IMPORTED
add_library(avcodec-57 SHARED IMPORTED)
#3. 设置动态库路径：${CMAKE_SOURCE_DIR}表示CmakeList文件目录 ${ANDROID_ABI}表示系统CPU架构
set_target_properties(avcodec-57
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libavcodec-57.so)
#其他so文件按照第2、3步重复操作即可，只需要替换对应的so库名称即可
add_library( avdevice-57 SHARED IMPORTED)
set_target_properties( avdevice-57
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libavdevice-57.so)


add_library( avfilter-6 SHARED IMPORTED)
set_target_properties( avfilter-6
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libavfilter-6.so)


add_library( avformat-57 SHARED IMPORTED)
set_target_properties( avformat-57
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libavformat-57.so)


add_library( avutil-55 SHARED IMPORTED)
set_target_properties( avutil-55
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libavutil-55.so)

add_library( postproc-54 SHARED IMPORTED)
set_target_properties( postproc-54
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libpostproc-54.so)

add_library( swresample-2 SHARED IMPORTED)
set_target_properties( swresample-2
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libswresample-2.so)


add_library( swscale-4 SHARED IMPORTED)
set_target_properties( swscale-4
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libswscale-4.so)

#4. 链接动态库
target_link_libraries(
        native-lib
        ${log-lib}
        # FFMPEG相关的类库
        avcodec-57
        avdevice-57
        avfilter-6
        avformat-57
        avutil-55
        postproc-54
        swresample-2
        swscale-4)

编写C++测试代码：

#include <jni.h>
#include <string>
#include <android/log.h>

//由于调用时是用C语言写的，所以也要用extern声明是C，否则编译时会报错
extern "C"{
#include <libavformat/avformat.h>
}


//定义打印Log方法
#define LOGI(FORMAT,...) __android_log_print(ANDROID_LOG_INFO,"MyPlayer",FORMAT,##__VA_ARGS__);

extern "C" JNIEXPORT jstring JNICALL
Java_cn_rongrtc_mylibrary_Demo_stringFromJNI(
        JNIEnv *env,
        jobject /* this */) {
    //注册所有的解码器
    av_register_all();
    //获取所有的解码器
    AVCodec *c_temp = av_codec_next(NULL);
     //遍历解码器并打印解码器名称
    while (c_temp != NULL)
    {
        switch (c_temp->type)
        {
            case AVMEDIA_TYPE_VIDEO:
                LOGI("[Video]:%s", c_temp->name);
                break;
            case AVMEDIA_TYPE_AUDIO:
                LOGI("[Audio]:%s", c_temp->name);
                break;
            default:
                LOGI("[Other]:%s", c_temp->name);
                break;
        }
        c_temp = c_temp->next;
    }
    std::string hello = "Hello from Demo C++";
    return env->NewStringUTF(hello.c_str());
}

编写Java层代码

public class Demo {
    // Used to load the 'native-lib' library on application startup.
    static {
        System.loadLibrary("native-lib");
        System.loadLibrary("avcodec-57");
        System.loadLibrary("avdevice-57");
        System.loadLibrary("avfilter-6");
        System.loadLibrary("avformat-57");
        System.loadLibrary("avutil-55");
        System.loadLibrary("postproc-54");
        System.loadLibrary("swresample-2");
        System.loadLibrary("swscale-4");
    }

    /**
     * A native method that is implemented by the 'native-lib' native library,
     * which is packaged with this application.
     */
    public static native String stringFromJNI();
}

遇到的问题

同步代码或编译时如果有类似的报错:

Error while executing process /Users/www/Library/Android/sdk/cmake/3.10.2.4988404/bin/cmake with arguments {--build /Users/www/codeSamples/ffmpeg/MusicPlayer/mylibrary/.externalNativeBuild/cmake/debug/arm64-v8a --target native-lib}
ninja: error: '../../../../src/main/jniLibs/arm64-v8a/libavcodec-57.so', needed by '../../../../build/intermediates/cmake/debug/obj/arm64-v8a/libnative-lib.so', missing and no known rule to make it

如果出现类似报错则有可能是你的so库不支持你手机CPU架构，你需要编译一份对应的CPU架构so库并拷贝到jniLibs目录下即可。具体如何编译可以参考上一篇文章Mac平台下编译FFMPEG