FFmpeg 编译 for Android

FFmpeg 评论

环境 ：
macOS Mojave
ndk - android-ndk-r14b
ffmpeg - V3.3.9 

在实操的过程中发现，别的版本编译不成功，没有过多做深入的研究，找到了这个可以编译的版本使用。

编译产物和demo已经放到github ：
https://github.com/kongxs/ffmpegDemo

1. 编译

1. 替换configure 中的内容
    主要是为了修改编译完的产物和命名，以便于Android平台使用
 

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


2. 编写脚本文件

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	#!/bin/bash

make clean
# NDK的路径，根据自己的安装位置进行设置
export TMPDIR=替换为自己的一个路径
export NDK=替换为自己的ndk路径
export SYSROOT=$NDK/platforms/android-21/arch-arm/
export TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64
export CPU=arm
export PREFIX=$(pwd)/android/$CPU
export ADDI_CFLAGS="-marm"
function build_one
{
./configure \
    --prefix=$PREFIX \
    --target-os=linux \
    --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
    --arch=arm \
    --sysroot=$SYSROOT \
    --extra-cflags="-Os -fpic $ADDI_CFLAGS" \
    --extra-ldflags="$ADDI_LDFLAGS" \
    --cc=$TOOLCHAIN/bin/arm-linux-androideabi-gcc \
    --nm=$TOOLCHAIN/bin/arm-linux-androideabi-nm \
    --enable-shared \
    --enable-runtime-cpudetect \
    --enable-gpl \
    --enable-small \
    --enable-cross-compile \
    --disable-debug \
    --disable-static \
    --disable-doc \
    --disable-asm \
    --disable-ffmpeg \
    --disable-ffplay \
    --disable-ffprobe \
    --disable-ffserver \
    --enable-postproc \
    --enable-avdevice \
    --disable-symver \
    --disable-stripping \
$ADDITIONAL_CONFIGURE_FLAG
sed -i '' 's/HAVE_LRINT 0/HAVE_LRINT 1/g' config.h
sed -i '' 's/HAVE_LRINTF 0/HAVE_LRINTF 1/g' config.h
sed -i '' 's/HAVE_ROUND 0/HAVE_ROUND 1/g' config.h
sed -i '' 's/HAVE_ROUNDF 0/HAVE_ROUNDF 1/g' config.h
sed -i '' 's/HAVE_TRUNC 0/HAVE_TRUNC 1/g' config.h
sed -i '' 's/HAVE_TRUNCF 0/HAVE_TRUNCF 1/g' config.h
sed -i '' 's/HAVE_CBRT 0/HAVE_CBRT 1/g' config.h
sed -i '' 's/HAVE_RINT 0/HAVE_RINT 1/g' config.h
make clean
# 这里是定义用几个CPU编译，我用4个，一般在5分钟之内编译完成
make -j4
make install
}
build_one

其中： 
TMPDIR为编译生成的临时文件存放的目录
SYSROOT为so文件支持的最低Android版本的平台目录
CPU为指定so文件支持的平台
PREFIX为生成的so文件存放目录
TOOLCHAIN为编译所使用的工具链目录
cross-prefix为编译所使用的工具链文件
enable和disable指定了需要编译的项
target-os为目标操作系统；

3. 执行脚本 
./build_android.sh 

等待执行结束会在  目录下生成编译产物 。  位于 android/arm 文件夹下
    include //  c语言头文件
    lib //	android可用的so

2. 引入Androidstudio开发环境

1. build.gradle 脚本配置 

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externalNativeBuild {
           cmake {
               cppFlags ""
           }
           ndk {
               abiFilters "armeabi-v7a"//添加平台过滤
           }
       }
       //指定libs文件夹
   sourceSets.main {
       jniLibs.srcDirs = ['libs']
       jni.srcDirs = []
   }
       
1. 添加依赖文件 
我们将第一步编译好的so放入libs文件夹，将 include文件中的头文件放到cpp文件夹 . 如下所示


2. CMakeLists.txt 文件编写 
    按照如下进行编写，将我们所有的so都在cmakelist文件中进行注册，联合编译

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	# 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
        src/main/cpp/Utils.c
        )

include_directories(${CMAKE_SOURCE_DIR}/src/main/cpp)

add_library(avcodec-57  # 库名字
            SHARED
            IMPORTED)
set_target_properties( avcodec-57
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/libs/armeabi-v7a/libavcodec-57.so)



add_library(libavdevice-57  # 库名字
        SHARED
        IMPORTED)
set_target_properties( libavdevice-57
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/libs/armeabi-v7a/libavdevice-57.so)



add_library(libavfilter-6  # 库名字
        SHARED
        IMPORTED)
set_target_properties( libavfilter-6
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/libs/armeabi-v7a/libavfilter-6.so)



add_library(libavformat-57  # 库名字
        SHARED
        IMPORTED)
set_target_properties( libavformat-57
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/libs/armeabi-v7a/libavformat-57.so)



add_library(libavutil-55  # 库名字
        SHARED
        IMPORTED)
set_target_properties( libavutil-55
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/libs/armeabi-v7a/libavutil-55.so)



add_library(libpostproc-54  # 库名字
        SHARED
        IMPORTED)
set_target_properties( libpostproc-54
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/libs/armeabi-v7a/libpostproc-54.so)



add_library(libswresample-2  # 库名字
        SHARED
        IMPORTED)
set_target_properties( libswresample-2
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/libs/armeabi-v7a/libswresample-2.so)



add_library(libswscale-4  # 库名字
        SHARED
        IMPORTED)
set_target_properties( libswscale-4
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/libs/armeabi-v7a/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
        libavdevice-57
        libavfilter-6
        libavformat-57
        libavutil-55
        libpostproc-54
        libswresample-2
        libswscale-4

                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )

3. 一些问题

1. 比如include 

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extern "C"
{
    #include "libavformat/avformat.h"
    #include "libavutil/log.h"
}

师学Android Developer

学而不思则罔，思而不学则殆。