导入FFMPEG动态库，视频解码实现

上一篇文章我们讲过了ffmpeg的编译，这一次我们讲一下在使用ffmpeg的时候遇到的问题

1.打开AndroidStudio创建一个C++项目，选择C++11
注意：新版本的AS把CMakeLists文件放在了cpp目录下，我们需要把这个文件放到src同级别目录下，同时修改一下app下的build.gradle 引用CMakeLists的配置

build.gradle配置

apply plugin: 'com.android.application'

android {
   
    compileSdkVersion 29
    buildToolsVersion "29.0.3"
    defaultConfig {
   
        applicationId "com.xxxx.ffmepg"
        minSdkVersion 21
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
   
            cmake {
   
                cppFlags "-std=c++11 -frtti -fexceptions"
                abiFilters 'x86_64'//这里因为是mac电脑模拟器的cpu架构选的是x86_64
            }
        }
    }
    buildTypes {
   
        release {
   
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
   
        cmake {
   
            path "CMakeLists.txt"//这个地方要修改默认生成的src/main/cpp/CMakeLists.txt
            version "3.6.0"//将默认的高版本调低，避免日志乱码
        }
    }
    sourceSets{
   
        main{
   
            jniLibs.srcDirs = ["src/main/jniLibs"]
        }
    }

}

将上一篇ffmpeg中编译出得x86_64和include文件分别放到cpp和jniLibs目录下

配置CMakeList.txt

# 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.


#remove some build warnings
#set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-deprecated-declarations ")


#FFMpeg配置
#FFmpeg配置目录
#这里就是为啥要将CMakeList放到src同级目录下的原因，使用便捷
set(lib_src_DIR ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI})
#配置编译的头文件
include_directories(${CMAKE_SOURCE_DIR}/src/main/cpp/include)


# 编解码(最重要的库)
add_library(
        avcodec-57
        SHARED
        IMPORTED)
set_target_properties(
        avcodec-57
        PROPERTIES IMPORTED_LOCATION
        ${lib_src_DIR}/libavcodec-57.so)


# 滤镜特效处理库
add_library(
        avfilter-6
        SHARED
        IMPORTED)
set_target_properties(
        avfilter-6
        PROPERTIES IMPORTED_LOCATION
        ${lib_src_DIR}/libavfilter-6.so)

# 封装格式处理库
add_library(
        avformat-57
        SHARED
        IMPORTED)
set_target_properties(
        avformat-57
        PROPERTIES IMPORTED_LOCATION
        ${lib_src_DIR}/libavformat-57.so)

# 工具库(大部分库都需要这个库的支持)
add_library(
        avutil-55
        SHARED
        IMPORTED)
set_target_properties(
        avutil-55
        PROPERTIES IMPORTED_LOCATION
        ${lib_src_DIR}/libavutil-55.so)

# 音频采样数据格式转换库
add_library(
        swresample-2
        SHARED
        IMPORTED)
set_target_properties(
        swresample-2
        PROPERTIES IMPORTED_LOCATION
        ${lib_src_DIR}/libswresample-2.so)

# 视频像素数据格式转换
add_library(
        swscale-4
        SHARED
        IMPORTED)
set_target_properties(
        swscale-4
        PROPERTIES IMPORTED_LOCATION
        ${lib_src_DIR}/libswscale-4.so)

#设置编译忽略过时方法使用导致的编译不通过
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11 -Wno-deprecated-declarations")
#判断编译器类型,如果是gcc编译器,则在编译选项中加入c++11支持
#if(CMAKE_COMPILER_IS_GNUCXX)
#    set(CMAKE_CXX_FLAGS "-std=c++11 ${CMAKE_CXX_FLAGS}")
#    message(STATUS "optional:-std=c++11")
#endif(CMAKE_COMPILER_IS_GNUCXX)

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).
        ${CMAKE_SOURCE_DIR}/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 )