FFmpeg 编译的so和include在android studio中的使用

上一篇博客讲了如何编译ffmpeg，产生适合在android上调用的so库文件和include头文件，下面讲讲如何在android studio中使用这些库文件来进行ndk开发

1、新建android 项目**，

注意勾选支持c/c++，然后将编译好的文件拷贝到libs目录下：

2、拷贝带版本号的库文件到libs/armeabi目录**（没有就新建）

3、 gradle将jni目录设置到libs****

      //     如果将so文件放在libs文件夹下得加上下面几句
        sourceSets {
        main {
        jniLibs.srcDirs = ['libs']
        }
    }

4.gradle设置 cpp文件目录 ，设置cpu编译库**

        externalNativeBuild {
            cmake {
                cppFlags ""
            }
            ndk{
            abiFilters "armeabi"
        }
        }

这里给出完整的gradle：

apply plugin: 'com.android.application'

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "com.example.lammy.ffmpegdemo"
        minSdkVersion 21
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags ""
            }
            ndk{
            abiFilters "armeabi"
        }
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    //     如果将so文件放在libs文件夹下得加上下面几句
    sourceSets {
        main {
            jniLibs.srcDirs = ['libs']
        }
    }

    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }

    }



}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:27.1.1'
    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'
}

5、配置CMakeLists.txt文件**

• 1、将libs/include导入
• 2、将so各个库添加进来（add_library 和 set_target_properties）

这里直接贴出来：

# 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.

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 )

include_directories(libs/include)
#设置so的路径
set(ffmpeg_DIR ${CMAKE_SOURCE_DIR}/libs)
add_library( avcodec-57
             SHARED
             IMPORTED)
set_target_properties( avcodec-57
                       PROPERTIES IMPORTED_LOCATION
                       ${ffmpeg_DIR}/armeabi/libavcodec-57.so)


add_library( avfilter-6
             SHARED
             IMPORTED)
set_target_properties( avfilter-6
                       PROPERTIES IMPORTED_LOCATION
                       ${ffmpeg_DIR}/armeabi/libavfilter-6.so)

add_library( avformat-57
             SHARED
             IMPORTED)
set_target_properties( avformat-57
                       PROPERTIES IMPORTED_LOCATION
                       ${ffmpeg_DIR}/armeabi/libavformat-57.so)

add_library( avutil-55
             SHARED
             IMPORTED)
set_target_properties( avutil-55
                       PROPERTIES IMPORTED_LOCATION
                       ${ffmpeg_DIR}/armeabi/libavutil-55.so)

add_library( swresample-2
             SHARED
             IMPORTED)
set_target_properties( swresample-2
                       PROPERTIES IMPORTED_LOCATION
                       ${ffmpeg_DIR}/armeabi/libswresample-2.so)

add_library( swscale-4
             SHARED
             IMPORTED)
set_target_properties( swscale-4
                       PROPERTIES IMPORTED_LOCATION
                       ${ffmpeg_DIR}/armeabi/libswscale-4.so)



# 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-57
                       avfilter-6
                       avformat-57
                       avutil-55
                       swresample-2
                       swscale-4
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )

6、编写jni文件和java文件

public class MainActivity extends AppCompatActivity {


    private int permissionRequestCode = 1;
    private String inputFilePath = new File(Environment.getExternalStorageDirectory()+
             "/a-lammytest/","test.mp4").getAbsolutePath();
    private String outputFilePath = new File(Environment.getExternalStorageDirectory()+
         "/a-lammytest/","output_yuv420p.yuv").getAbsolutePath();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        requestPermissions();

    }

    private String permissions[] = new String[]{
            Manifest.permission.WRITE_EXTERNAL_STORAGE,
            Manifest.permission.READ_EXTERNAL_STORAGE,

    };


    private void requestPermissions(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            for(int i =0; i < permissions.length ; i ++) {
                if( checkSelfPermission(permissions[0]) == PackageManager.PERMISSION_DENIED){
                    requestPermissions(permissions ,permissionRequestCode );
                    return;
     //         Toast.makeText(this , "请打开"+permissions[0]+"权限",Toast.LENGTH_LONG).show();
                }
            }
            decode(inputFilePath, outputFilePath);
        }else{
            decode(inputFilePath, outputFilePath);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, 
    @NonNull int[] grantResults) {

        if(requestCode ==permissionRequestCode ){

            for(int result:grantResults){
                if(result == PackageManager.PERMISSION_DENIED){
                    return;
                }
            }

            decode(inputFilePath, outputFilePath);

        }
    }
}

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

    public native static void decode(String input,String output);

}

jni中解码demo参考：https://www.cnblogs.com/CoderTian/p/6651343.html

extern "C" {
//编码
#include "libavcodec/avcodec.h"
//封装格式处理
#include "libavformat/avformat.h"
//像素处理
#include "libswscale/swscale.h"
}
#define FFLOGI(FORMAT,...) __android_log_print(ANDROID_LOG_INFO,"ffmpeg",FORMAT,##__VA_ARGS__);
#define FFLOGE(FORMAT,...) __android_log_print(ANDROID_LOG_ERROR,"ffmpeg",FORMAT,##__VA_ARGS__);

extern "C"
JNIEXPORT void JNICALL
Java_com_example_lammy_ffmpegdemo_FFmpegUtil_decode(JNIEnv *env, jclass type, jstring input_,
                                                  jstring output_) {
    const char *input = env->GetStringUTFChars(input_, 0);
    const char *output = env->GetStringUTFChars(output_, 0);

    // TODO
    //1.注册所有组件
    av_register_all();

    //封装格式上下文，统领全局的结构体，保存了视频文件封装格式的相关信息
    AVFormatContext *pFormatCtx = avformat_alloc_context();

    //2.打开输入视频文件
    if (avformat_open_input(&pFormatCtx, input, NULL, NULL) != 0)
    {
        FFLOGE("%s","无法打开输入视频文件");
        return;
    }

    //3.获取视频文件信息
    if (avformat_find_stream_info(pFormatCtx,NULL) < 0)
    {
        FFLOGE("%s","无法获取视频文件信息");
        return;
    }

    //获取视频流的索引位置
    //遍历所有类型的流（音频流、视频流、字幕流），找到视频流
    int v_stream_idx = -1;
    int i = 0;
    //number of streams
    for (; i < pFormatCtx->nb_streams; i++)
    {
        //流的类型
        if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
        {
            v_stream_idx = i;
            break;
        }
    }

    if (v_stream_idx == -1)
    {
        FFLOGE("%s","找不到视频流\n");
        return;
    }

    //只有知道视频的编码方式，才能够根据编码方式去找到解码器
    //获取视频流中的编解码上下文
    AVCodecContext *pCodecCtx = pFormatCtx->streams[v_stream_idx]->codec;
    //4.根据编解码上下文中的编码id查找对应的解码
    AVCodec *pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    if (pCodec == NULL)
    {
        FFLOGE("%s","找不到解码器\n");
        return;
    }

    //5.打开解码器
    if (avcodec_open2(pCodecCtx,pCodec,NULL)<0)
    {
        FFLOGE("%s","解码器无法打开\n");
        return;
    }

    //输出视频信息
    FFLOGI("视频的文件格式：%s",pFormatCtx->iformat->name);
    FFLOGI("视频时长：%d", (pFormatCtx->duration)/1000000);
    FFLOGI("视频的宽高：%d,%d",pCodecCtx->width,pCodecCtx->height);
    FFLOGI("解码器的名称：%s",pCodec->name);

    //准备读取
    //AVPacket用于存储一帧一帧的压缩数据（H264）
    //缓冲区，开辟空间
    AVPacket *packet = (AVPacket*)av_malloc(sizeof(AVPacket));

    //AVFrame用于存储解码后的像素数据(YUV)
    //内存分配
    AVFrame *pFrame = av_frame_alloc();
    //YUV420
    AVFrame *pFrameYUV = av_frame_alloc();
    //只有指定了AVFrame的像素格式、画面大小才能真正分配内存
    //缓冲区分配内存
    uint8_t *out_buffer = (uint8_t *)av_malloc(avpicture_get_size(AV_PIX_FMT_YUV420P, pCodecCtx->width,
     pCodecCtx->height));
    //初始化缓冲区
    avpicture_fill((AVPicture *)pFrameYUV, out_buffer, AV_PIX_FMT_YUV420P, pCodecCtx->width, 
    pCodecCtx->height);

    //用于转码（缩放）的参数，转之前的宽高，转之后的宽高，格式等
    struct SwsContext *sws_ctx = sws_getContext(pCodecCtx->width,pCodecCtx->height,pCodecCtx->pix_fmt,
                                                pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P，
                                                SWS_BICUBIC, NULL, NULL, NULL);
    int got_picture, ret;

    FILE *fp_yuv = fopen(output, "wb+");

    int frame_count = 0;

    //6.一帧一帧的读取压缩数据
    while (av_read_frame(pFormatCtx, packet) >= 0)
    {
        //只要视频压缩数据（根据流的索引位置判断）
        if (packet->stream_index == v_stream_idx)
        {
            //7.解码一帧视频压缩数据，得到视频像素数据
            ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
            if (ret < 0)
            {
                FFLOGE("%s","解码错误");
                return;
            }

            //为0说明解码完成，非0正在解码
            if (got_picture)
            {
                //AVFrame转为像素格式YUV420，宽高
                //2 6输入、输出数据
                //3 7输入、输出画面一行的数据的大小 AVFrame 转换是一行一行转换的
                //4 输入数据第一列要转码的位置 从0开始
                //5 输入画面的高度
                sws_scale(sws_ctx, pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
                          pFrameYUV->data, pFrameYUV->linesize);

                //输出到YUV文件
                //AVFrame像素帧写入文件
                //data解码后的图像像素数据（音频采样数据）
                //Y 亮度 UV 色度（压缩了） 人对亮度更加敏感
                //U V 个数是Y的1/4
                int y_size = pCodecCtx->width * pCodecCtx->height;
                fwrite(pFrameYUV->data[0], 1, y_size, fp_yuv);
                fwrite(pFrameYUV->data[1], 1, y_size / 4, fp_yuv);
                fwrite(pFrameYUV->data[2], 1, y_size / 4, fp_yuv);

                frame_count++;
                FFLOGI("解码第%d帧",frame_count);
            }
        }

        //释放资源
        av_free_packet(packet);
    }

    fclose(fp_yuv);

    av_frame_free(&pFrame);

    avcodec_close(pCodecCtx);

    avformat_free_context(pFormatCtx);



    env->ReleaseStringUTFChars(input_, input);
    env->ReleaseStringUTFChars(output_, output);
}

最后注意添加内存卡的访问权限：

    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

运行的结果是将mp4格式的视频 解码后编码为 YUV420格式的视频，yuv播发器打开，并且设置号视频参数
1、yuv播发器：YUV Player Deluxe打开：

2、设置参数为：

代码：这里给出完整代码，欢迎各位老铁去下载。