Android Studio中使用FFMPEG（CMake）

逃离我推掉我的手 2022-06-17 10:44 273阅读 0赞

**本文是转载的，不过根据我当前的例子做了下调整**

1.下载 FFmpeg 源码  
git clone [https://git.ffmpeg.org/ffmpeg.git][https_git.ffmpeg.org_ffmpeg.git]  
这一步可能会花比较长的时间，我是在Mac电脑下编译的，Windows下编译我不是很清楚。

2.编译 FFmpeg for Android  
2.1.修改 FFmpeg 的 configure  
由于FFMPEG默认编译出来的动态库文件名的版本号在.so之后（例如“libavcodec.so.5.100.1”），但是android平台不能识别这样文件名，所以我们需要修改FFMPEG生成的动态库的文件名。

打开 configure 文件，找到：

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)'

修改为

SLIBNAME_WITH_MAJOR='$(SLIBPREF)$(FULLNAME)-$(LIBMAJOR)$(SLIBSUF)'  
    LIB_INSTALL_EXTRA_CMD='$$(RANLIB)"$(LIBDIR)/$(LIBNAME)"'  
    SLIB_INSTALL_NAME='$(SLIBNAME_WITH_MAJOR)'  
    SLIB_INSTALL_LINKS='$(SLIBNAME)'

2.2.编写 Android 编译脚本

*  注意这个脚本网上非常多，而且ffmpeg的版本也不一样（我使用3.3版本就编译出来的不是.so文件），所以你会发现也不一样，这个脚本也不是很懂照葫芦画瓢而已，有问题的话还是学学脚本吧。具体的编译文档请参考文章后面的连接。

#!/bin/sh
    NDK=/Users/Shared/Development/android_sdk/ndk-bundle
    SYSROOT=$NDK/platforms/android-21/arch-arm
    TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64
    function build_one
    {
    ./configure \
    --prefix=$PREFIX \ --enable-shared \ --disable-static \ --disable-doc \ --disable-ffmpeg \ --disable-ffplay \ --disable-ffprobe \ --disable-ffserver \ --disable-avdevice \ --disable-doc \ --disable-symver \ --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \ --target-os=linux \ --arch=arm \ --enable-cross-compile \ --sysroot=$SYSROOT \ --extra-cflags="-Os -fpic $ADDI_CFLAGS" \ --extra-ldflags="$ADDI_LDFLAGS" \ $ADDITIONAL_CONFIGURE_FLAG
    make clean
    make
    make install
    }
    CPU=arm
    PREFIX=$(pwd)/android/$CPU
    ADDI_CFLAGS="-marm"
    build_one

2.3.编译  
执行上面的脚本编译出我们需要的动态库

./build\_android.sh  
进入android/$CPU目录可以看到生成的动态库和我们需要的头文件

复制代码  
.  
└── arm  
├── include  
│ ├── libavcodec  
│ ├── libavfilter  
│ ├── libavformat  
│ ├── libavutil  
│ ├── libswresample  
│ └── libswscale  
└── lib  
├── libavcodec-57.so  
├── libavcodec.so -> libavcodec-57.so  
├── libavfilter-6.so  
├── libavfilter.so -> libavfilter-6.so  
├── libavformat-57.so  
├── libavformat.so -> libavformat-57.so  
├── libavutil-55.so  
├── libavutil.so -> libavutil-55.so  
├── libswresample-2.so  
├── libswresample.so -> libswresample-2.so  
├── libswscale-4.so  
├── libswscale.so -> libswscale-4.so  
└── pkgconfig  
复制代码  
3.将上一步生成的头文件和库文件导入到Android Studio工程中  
首先新建一个工程，并且勾选 Include C++ Support 即可得到一个基于CMake的模板工程。目录结构如下所示

.  
├── app  
│ ├── app.iml  
│ ├── build  
│ │ ├── generated  
│ │ │ ├── res  
│ │ │ └── source  
│ │ ├── intermediates  
│ │ │ ├── blame  
│ │ │ ├── incremental  
│ │ │ ├── manifest  
│ │ │ ├── manifests  
│ │ │ ├── res  
│ │ │ ├── rs  
│ │ │ └── symbols  
│ │ └── outputs  
│ │ └── logs  
│ ├── build.gradle  
│ ├── CMakeLists.txt  
│ ├── CMakeLists.txt~  
│ ├── libs  
│ │ ├── armeabi  
│ │ │ ├── libavcodec-57.so  
│ │ │ ├── libavfilter-6.so  
│ │ │ ├── libavformat-57.so  
│ │ │ ├── libavutil-55.so  
│ │ │ ├── libswresample-2.so  
│ │ │ └── libswscale-4.so  
│ │ └── include  
│ │ ├── libavcodec  
│ │ ├── libavfilter  
│ │ ├── libavformat  
│ │ ├── libavutil  
│ │ ├── libswresample  
│ │ └── libswscale  
│ ├── proguard-rules.pro  
│ └── src  
│ ├── androidTest  
│ │ └── java  
│ ├── main  
│ │ ├── AndroidManifest.xml  
│ │ ├── cpp  
│ │ ├── java  
│ │ └── res  
│ └── test  
│ └── java  
├── build  
│ ├── android-profile  
│ │ └── profile-2017-03-31-23-04-31-347.rawproto  
│ └── generated  
│ └── mockable-android-25.jar  
├── build.gradle  
├── FFMPEGTest.iml  
├── gradle  
│ └── wrapper  
│ ├── gradle-wrapper.jar  
│ └── gradle-wrapper.properties  
├── gradle.properties  
├── gradlew  
├── gradlew.bat  
├── local.properties  
└── settings.gradle

然后将上面编译FFMPEG生成的头文件和动态库拷贝到app/libs目录下，拷贝完后的目录结构如下所示

├── app  
│ ├── libs  
│ │ ├── armeabi  
│ │ │ ├── libavcodec-57.so  
│ │ │ ├── libavfilter-6.so  
│ │ │ ├── libavformat-57.so  
│ │ │ ├── libavutil-55.so  
│ │ │ ├── libswresample-2.so  
│ │ │ └── libswscale-4.so  
│ │ └── include  
│ │ ├── libavcodec  
│ │ ├── libavfilter  
│ │ ├── libavformat  
│ │ ├── libavutil  
│ │ ├── libswresample  
│ │ └── libswscale  
│ ├── proguard-rules.pro  
│ └── src  
这样还没完，我当时就是这样直接去编译，然后就踩了一个大坑，APP启动之后一直crash，原因就是没有找到我们在java文件里load的动态库。为什么呢？原因是在编译的时候，我们根本没有将我们的动态库打包到APP中，我们还需要修改app/build.gradle将我们放在libs目录下的动态库打包到APP中去

apply plugin: 'com.android.application'
    
    android {
        compileSdkVersion 25
        buildToolsVersion "25.0.2"
        defaultConfig {
            applicationId "com.arshowbaby.ffmpeg"
            minSdkVersion 21
            targetSdkVersion 25
            versionCode 1
            versionName "1.0"
            testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
            externalNativeBuild {
                cmake {
                    cppFlags "-frtti -fexceptions"
                }
                ndk {
                    abiFilters "armeabi"
                }
            }
        }
        buildTypes {
            release {
                minifyEnabled false
                proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            }
        }
        externalNativeBuild {
            cmake {
                path "CMakeLists.txt"
            }
        }
    
        sourceSets {
            main {
                jniLibs.srcDirs = ["libs"]
            }
        }
    }
    
    dependencies {
        compile fileTree(dir: 'libs', include: ['*.jar'])
        androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
            exclude group: 'com.android.support', module: 'support-annotations'
        })
        compile 'com.android.support:appcompat-v7:25.3.1'
        compile 'com.android.support.constraint:constraint-layout:1.0.2'
        compile 'com.android.support:design:25.3.1'
        testCompile 'junit:junit:4.12'
    }

紧接着就是来编写我们的CMakeLists.txt文件来编译我们的动态库和native源文件了

# 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 )
    
    # 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.
    
    set(distribution_DIR ../../../../libs)
    
    add_library( avcodec-57
                 SHARED
                 IMPORTED)
    set_target_properties( avcodec-57
                           PROPERTIES IMPORTED_LOCATION
                           ${distribution_DIR}/armeabi/libavcodec-57.so)
    
    add_library( avfilter-6
                 SHARED
                 IMPORTED)
    set_target_properties( avfilter-6
                           PROPERTIES IMPORTED_LOCATION
                           ${distribution_DIR}/armeabi/libavfilter-6.so)
    
    add_library( avformat-57
                 SHARED
                 IMPORTED)
    set_target_properties( avformat-57
                           PROPERTIES IMPORTED_LOCATION
                           ${distribution_DIR}/armeabi/libavformat-57.so)
    
    add_library( avutil-55
                 SHARED
                 IMPORTED)
    set_target_properties( avutil-55
                           PROPERTIES IMPORTED_LOCATION
                           ${distribution_DIR}/armeabi/libavutil-55.so)
    
    add_library( swresample-2
                 SHARED
                 IMPORTED)
    set_target_properties( swresample-2
                           PROPERTIES IMPORTED_LOCATION
                           ${distribution_DIR}/armeabi/libswresample-2.so)
    
    add_library( swscale-4
                 SHARED
                 IMPORTED)
    set_target_properties( swscale-4
                           PROPERTIES IMPORTED_LOCATION
                           ${distribution_DIR}/armeabi/libswscale-4.so)
    
    include_directories(libs/include)
    
    
    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}
                           )

这样基本上就大功告成了。

4.使用FFMPEG  
下面我们将通过一个小例子来看一下怎样使用FFMPEG。使用FFMPEG进行视频解码（音频和视频很相似）的一般流程如下图所示

首先需要在JAVA文件中加载我们需要的动态库

//MainActivity.java
    public class MainActivity extends AppCompatActivity { 
    
        // 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");
        }
    
        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
            setSupportActionBar(toolbar);
    
            FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
            fab.setOnClickListener(new View.OnClickListener()
            {
                @Override
                public void onClick(View view)
                {
                    File inputFile = new File(Environment.getExternalStorageDirectory(), "mv.mp4");
                    if (!inputFile.exists())
                    {
                        Snackbar.make(view, "文件不存在", Snackbar.LENGTH_LONG).setAction("Action", null)
                                .show();
                        return;
                    }
                    File outputFile = new File(Environment.getExternalStorageDirectory(),
                            "output_mv.yuv");
                    decode(inputFile.getAbsolutePath(), outputFile.getAbsolutePath());
                }
            });
    
            // Example of a call to a native method
            TextView tv = (TextView) findViewById(R.id.sample_text);
            tv.setText(stringFromJNI());
        }
    
        @Override
        public boolean onCreateOptionsMenu(Menu menu)
        {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.menu_main, menu);
            return true;
        }
    
        @Override
        public boolean onOptionsItemSelected(MenuItem item)
        {
            // Handle action bar item clicks here. The action bar will
            // automatically handle clicks on the Home/Up button, so long
            // as you specify a parent activity in AndroidManifest.xml.
            int id = item.getItemId();
    
            //noinspection SimplifiableIfStatement
            if (id == R.id.action_settings)
            {
                return true;
            }
    
            return super.onOptionsItemSelected(item);
        }
    
        /** * A native method that is implemented by the 'native-lib' native library, * which is packaged with this application. */
        public native String stringFromJNI();
    
        public native void decode(String input, String output);
    }

然后在native代码中实现主要逻辑

#include <jni.h>
    #include <string>
    #include <android/log.h>
    
    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 jstring JNICALL
    Java_com_arshowbaby_ffmpeg_MainActivity_stringFromJNI(
            JNIEnv *env,
            jobject /* this */) {
        std::string hello = "Hello from C++";
        return env->NewStringUTF(hello.c_str());
    }
    
    extern "C"
    JNIEXPORT void JNICALL
    Java_com_arshowbaby_ffmpeg_MainActivity_decode(JNIEnv *env, jclass type, jstring input_,
                                                         jstring output_) {
        //获取输入输出文件名
        const char *input = env->GetStringUTFChars(input_, 0);
        const char *output = env->GetStringUTFChars(output_, 0);
    
        //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);
    }

记得在Manifest文件中添加需要的权限

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

**但是，我使用我的例子运行后无法打开视频，不知道为什么打不开**。最后简单了解一下FFMPEG中使用的几个主要数据结构的作用：

![这里写图片描述][SouthEast]

最后感谢无私的分享，有你们我们才能进步。  
AndroidStudio 中使用FFMPEG：[http://www.cnblogs.com/CoderTian/p/6651343.html\#undefined][http_www.cnblogs.com_CoderTian_p_6651343.html_undefined]  
手把手图文并茂教你用Android Studio编译FFmpeg库并移植：[http://blog.csdn.net/hejjunlin/article/details/52661331][http_blog.csdn.net_hejjunlin_article_details_52661331]

附上示例地址：[https://github.com/Xanthuim/FFmpegSample][https_github.com_Xanthuim_FFmpegSample]

[https_git.ffmpeg.org_ffmpeg.git]: https://git.ffmpeg.org/ffmpeg.git
[SouthEast]: /images/20220617/7fb68c06a16c446daa85719b4d5116c3.png
[http_www.cnblogs.com_CoderTian_p_6651343.html_undefined]: http://www.cnblogs.com/CoderTian/p/6651343.html#undefined
[http_blog.csdn.net_hejjunlin_article_details_52661331]: http://blog.csdn.net/hejjunlin/article/details/52661331
[https_github.com_Xanthuim_FFmpegSample]: https://github.com/Xanthuim/FFmpegSample