1.ffmpeg默认使用gcc编译，在android上无法使用，否则各种报错，所以要用ndk的clang编译

2.下载ffmpeg源码
修改configure文件，增加命令 cross_prefix_clang
修改以下命令

cc_default="${cross_prefix}${cc_default}"
cxx_default="${cross_prefix}${cxx_default}"

修改后

cc_default="${cross_prefix_clang}${cc_default}"
cxx_default="${cross_prefix_clang}${cxx_default}"

3.新建脚本文件，ffmpeg目录下执行脚本文件即可。
编译32位，则ARCH改为arm，CPU改为armv7-a，TARGET改为armv7a-linux-androideabi
注意，r25版本的ndk移除了交叉编译工具，改成了llvm，所以要把交叉编译工具路径指向llvm的路径

#!/bin/bash
set -x
# 目标Android版本
API=21
ARCH=arm64
CPU=armv8-a
TARGET=aarch64-linux-android
#so库输出目录
OUTPUT=/root/Desktop/compile/ffmpeg/build_$CPU
#NDK路径
NDK=/root/Desktop/compile/ndk/android-ndk-r25c
#NDK=/root/Desktop/compile/ndk/android-ndk-r20b
# 编译工具链路径
TOOLCHAIN=$NDK/toolchains/llvm/prebuilt/linux-x86_64
# 编译环境
SYSROOT=$TOOLCHAIN/sysroot#OPTIMIZE_CFLAGS="-mfloat-abi=softfp -mfpu=vfp -marm -march=$CPU -DBIONIC_IOCTL_NO_SIGNEDNESS_OVERLOAD"#point build to llvm 
ln -s $TOOLCHAIN/bin/llvm-ar $TOOLCHAIN/bin/$TARGET-ar
ln -s $TOOLCHAIN/bin/llvm-nm $TOOLCHAIN/bin/$TARGET-nm
ln -s $TOOLCHAIN/bin/llvm-ranlib $TOOLCHAIN/bin/$TARGET-ranlib
ln -s $TOOLCHAIN/bin/llvm-strip $TOOLCHAIN/bin/$TARGET-stripfunction build
{./configure \--prefix=$OUTPUT \--target-os=android \--arch=$ARCH \--cpu=$CPU \--enable-cross-compile \--enable-shared \--disable-static \--disable-vulkan \--sysroot=$SYSROOT \--cross-prefix=$TOOLCHAIN/bin/$TARGET- \--cross-prefix-clang=$TOOLCHAIN/bin/$TARGET$API- \make clean allmake install
}build

4.android studio 导入
5.cmake配置

cmake_minimum_required(VERSION 3.22.1)# Declares and names the project.project("teskndk")# 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.#set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")
#include_directories(${CMAKE_CURRENT_SOURCE_DIR}/include)
#set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -L${CMAKE_CURRENT_SOURCE_DIR}/../../../libs/")add_library( # Sets the name of the library.teskndk# Sets the library as a shared library.SHARED# Provides a relative path to your source file(s).native-lib.cpp)add_library(avcodec SHARED IMPORTED)
set_target_properties(avcodec PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../../../libs/${ANDROID_ABI}/libavcodec.so)add_library(avdevice SHARED IMPORTED)
set_target_properties(avdevice PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../../../libs/${ANDROID_ABI}/libavdevice.so)add_library(avfilter SHARED IMPORTED)
set_target_properties(avfilter PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../../../libs/${ANDROID_ABI}/libavfilter.so)add_library(avformat SHARED IMPORTED)
set_target_properties(avformat PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../../../libs/${ANDROID_ABI}/libavformat.so)add_library(avutil SHARED IMPORTED)
set_target_properties(avutil PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../../../libs/${ANDROID_ABI}/libavutil.so)add_library(swresample SHARED IMPORTED)
set_target_properties(swresample PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../../../libs/${ANDROID_ABI}/libswresample.so)add_library(swscale SHARED IMPORTED)
set_target_properties(swscale PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../../../libs/${ANDROID_ABI}/libswscale.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.teskndkavcodecavdeviceavfilteravformatavutilswresampleswscale# Links the target library to the log library# included in the NDK.${log-lib})

成功运行