[移动开发]Android集成FFmpeg

Android集成FFmpeg

参考：https://www.jianshu.com/p/2c9918546edc

上一篇文章我们在mac下编译出了供Android平台使用的FFmpeg产物，这篇文章继续讲怎么在Android平台上集成FFmepg。

本文是参考别的文章写的，出处已在文首和文末处说明。之所以说只参考，而不是转载，一是我对原文进行了精简，二是因为我在自己尝试时发现了两个问题，并解决了这两个问题，可以说是一种补充吧。

实现步骤

一、新建工程

在Android Studio中选择新建Native C++功能，我的Android Studio版本是4.1.2

二、导入FFmepg文件

1. 在main下新建nativeLibs/armeabi-v7a目录，将上篇文章的so导入

   为什么是nativeLibs而不是jniLibs，是因为我按原文新建jniLibs后编译报错。后经搜索发现在AS升级4.0.1后会有报Android Studio带C++项目提示More than one file was found with OS independent path问题

   详见：https://blog.k-res.net/archives/2592.html

2. 导入头文件

   在cpp文件夹下新建ffmpeg/include目录在其中导入上篇文章中的include文件下的所有文件夹

3. 修改CMakeList.txt

   注意so文件的目录，本文是nativeLibs

   # 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 3.10.2)
   
   # 支持gnu++11
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")
   
   # 1. 定义so库和头文件所在目录，方面后面使用，注意！！是nativeLibs
   set(ffmpeg_lib_dir ${CMAKE_SOURCE_DIR}/../nativeLibs/${ANDROID_ABI})
   set(ffmpeg_head_dir ${CMAKE_SOURCE_DIR}/ffmpeg)
   
   # 2. 添加头文件目录
   include_directories(${ffmpeg_head_dir}/include)
   
   # 3. 添加ffmpeg相关的so库
   add_library( avutil
           SHARED
           IMPORTED )
   set_target_properties( avutil
           PROPERTIES IMPORTED_LOCATION
           ${ffmpeg_lib_dir}/libavutil.so )
   
   add_library( swresample
           SHARED
           IMPORTED )
   set_target_properties( swresample
           PROPERTIES IMPORTED_LOCATION
           ${ffmpeg_lib_dir}/libswresample.so )
   
   add_library( avcodec
           SHARED
           IMPORTED )
   set_target_properties( avcodec
           PROPERTIES IMPORTED_LOCATION
           ${ffmpeg_lib_dir}/libavcodec.so )
   
   add_library( avfilter
           SHARED
           IMPORTED)
   set_target_properties( avfilter
           PROPERTIES IMPORTED_LOCATION
           ${ffmpeg_lib_dir}/libavfilter.so )
   
   add_library( swscale
           SHARED
           IMPORTED)
   set_target_properties( swscale
           PROPERTIES IMPORTED_LOCATION
           ${ffmpeg_lib_dir}/libswscale.so )
   
   add_library( avformat
           SHARED
           IMPORTED)
   set_target_properties( avformat
           PROPERTIES IMPORTED_LOCATION
           ${ffmpeg_lib_dir}/libavformat.so )
   
   add_library( avdevice
           SHARED
           IMPORTED)
   set_target_properties( avdevice
           PROPERTIES IMPORTED_LOCATION
           ${ffmpeg_lib_dir}/libavdevice.so )
   
   # 查找代码中使用到的系统库
   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 )
   
   # 配置目标so库编译信息
   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).
           native-lib.cpp
           )
   
   # 指定编译目标库时，cmake要链接的库
   target_link_libraries(
   
           # 指定目标库，native-lib 是在上面 add_library 中配置的目标库
           native-lib
   
           # 4. 连接 FFmpeg 相关的库
           avutil
           swresample
           avcodec
           avfilter
           swscale
           avformat
           avdevice
   
           # Links the target library to the log library
           # included in the NDK.
           ${log-lib} )
   

4. 新建测试方法

   在nateive-lib.cpp中添加测试方法

   这里是我遇到的第二个问题，原文中使用的方法av_codec_next在我这个环境中已经失效了，于是搜索后，找到解决方案：https://www.coder.work/article/1988131

   #include <jni.h>
   #include <string>
   #include <unistd.h>
   
   extern "C" {
   #include <libavcodec/avcodec.h>
   #include <libavformat/avformat.h>
   #include <libavfilter/avfilter.h>
   #include <libavcodec/jni.h>
   
   JNIEXPORT jstring JNICALL
   Java_com_hdym_myapplication_MainActivity_ffmpegInfo(JNIEnv *env, jobject  /* this */) {
   
       char info[40000] = {0};
       const AVCodec *c_temp = nullptr;
       void *i = 0;
   
       while ((c_temp = av_codec_iterate(&i))) {
           if (c_temp->decode != NULL) {
               sprintf(info, "%sdecode:", info);
               switch (c_temp->type) {
                   case AVMEDIA_TYPE_VIDEO:
                       sprintf(info, "%s(video):", info);
                       break;
                   case AVMEDIA_TYPE_AUDIO:
                       sprintf(info, "%s(audio):", info);
                       break;
                   default:
                       sprintf(info, "%s(other):", info);
                       break;
               }
               sprintf(info, "%s[%10s]\n", info, c_temp->name);
           } else {
               sprintf(info, "%sencode:", info);
           }
       }
       return env->NewStringUTF(info);
   }
   }
   

5. 测试使用

   import android.os.Bundle
   import android.widget.TextView
   import androidx.appcompat.app.AppCompatActivity
   
   class MainActivity : AppCompatActivity() {
       companion object {
           // Used to load the 'native-lib' library on application startup.
           init {
               System.loadLibrary("native-lib")
           }
       }
   
       override fun onCreate(savedInstanceState: Bundle?) {
           super.onCreate(savedInstanceState)
           setContentView(R.layout.activity_main)
   
           // Example of a call to a native method
           val tv = findViewById<TextView>(R.id.sample_text)
           tv.text = ffmpegInfo()
       }
       private external fun ffmpegInfo(): String
   }
   

6. 运行结果
   

以上

参考：https://www.jianshu.com/p/2c9918546edc