使用最新的FFmpeg库和NDK在Android中编译简单库的错误

Question

I'm trying to get FFmpeg working in Android , and after successfuly compiled it on Ubuntu 64bit , and created the Android.mk under source/ffmpeg-3.4.2/android/arm folder and also the Android.mk in my own Android project ! i'm unable to compile a simple program and create the .so file ! By the way i've searched over the net and in Stackoverflow for 2 days now without luck ! here is the code Android.mk

LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE    := MyLibrary
LOCAL_SRC_FILES := MyNativeFunctions.c
LOCAL_LDLIBS := -lz -llog
LOCAL_STATIC_LIBRARIES := libavformat_static libavcodec_static libavutil_static
include $(BUILD_SHARED_LIBRARY)

$(call import-module,ffmpeg-3.2.4/android/arm)

The native functions

    #include <libavformat/avformat.h>
    #include <libavcodec/avcodec.h>
    #include <libavutil/avutil.h>

    #include <android/log.h>
    #define LOG_TAG "mylib"
    #define LOGI(...)  __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)
    #define LOGE(...)  __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)
    jint Java_com_example_home_hellondk_MyNativeFunctions_TestNdk(JNIEnv * env, jobject this, jstring filename)
    {
         av_register_all();

return 0;
}

when i use NDK-BUILD here is the error i got :

/home/home/Android/Sdk/ndk-bundle/sources/ffmpeg-3.2.4/android/arm/lib/libavformat.a: error adding symbols: File in wrong format
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [obj/local/arm64-v8a/libMyLibrary.so] Error 1

[EDIT] Build_android.sh

#!/bin/bash
NDK=/home/home/Android/Sdk/ndk-bundle
SYSROOT=$NDK/platforms/android-24/arch-arm/
TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64
 function build_one
{
./configure \
--prefix=$PREFIX \
--disable-shared \
--enable-static \
--disable-doc \
--disable-ffmpeg \
--disable-ffplay \
--disable-ffprobe \
--disable-ffserver \
--disable-avdevice \
--disable-doc \
--disable-symver \
--cross-prefix=$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

[EDIT] The problem has been solved by adding the missing library in LOCAL_STATIC_LIBRARIES := libavformat_static libavcodec_static libswscale_static libavutil_static libswresample_static and for all users of Android Studio do not forget to add this line to your gradle otherwise it won't work.

sourceSets.main {
        jni.srcDirs = []
        jniLibs.srcDir 'src/main/libs'
    }

Best regards

Answer 1

You're only building ffmpeg for arm32 but you're building your app for all ABIs.

Here in your ffmpeg build script you're targeting arm specifically:

SYSROOT=$NDK/platforms/android-24/arch-arm/

And from the error output you can see it was building arm64:

make: *** [obj/local/arm64-v8a/libMyLibrary.so] Error 1

Either limit your ndk-build to building only arm32 ( APP_ABI := armeabi-v7a in your Application.mk ) or build ffmpeg for the other architectures as well.

By the way, you'll have an easier time building autoconf projects with the NDK if you use https://developer.android.com/ndk/guides/standalone_toolchain.html