问题
Tried so many ways to solve problem but no luck. Here is my Android.mk:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := avcodec
LOCAL_SRC_FILES :=libavcodec.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := avutil
LOCAL_SRC_FILES :=libavutil.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := swscale
LOCAL_SRC_FILES :=libswscale.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := avformat
LOCAL_SRC_FILES :=libavformat.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := avresample
LOCAL_SRC_FILES :=libavresample.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := swresample
LOCAL_SRC_FILES :=libswresample.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := x264
LOCAL_SRC_FILES :=libx264.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
#------------------------------------------
LOCAL_C_INCLUDES := $(LOCAL_PATH)\
$(LOCAL_PATH)/include
LOCAL_MODULE := media
LOCAL_SRC_FILES := \
P_Decoding.cpp \
P_Encoding.cpp \
wrapper_for_ffmpeg.cpp
LOCAL_CPPFLAGS := -std=c++11 -pthread -frtti -fexceptions
LOCAL_ARM_MODE := arm
LOCAL_STATIC_LIBRARIES := avcodec avutil swscale avformat avresample swresample x264
LOCAL_LDLIBS := -llog -ljnigraphics -landroid -lz -lEGL
LOCAL_CPP_FEATURES := rtti exceptions
include $(BUILD_SHARED_LIBRARY)
In jni folder there are all header .hpp files related to .cpp files on makefile, also there are all static .a libraries and "include" folder where all header files related to static libraries are. I'm using ndk9c version. Here is part of error log:
[armeabi-v7a] Compile++ thumb: media <= P_Decoding.cpp
[armeabi-v7a] Compile++ thumb: media <= P_Encoding.cpp
[armeabi-v7a] Compile++ thumb: media <= wrapper_for_ffmpeg.cpp
/home/pro/android-ndk-r9c/toolchains/llvm-3.3/prebuilt/linux-x86/bin/clang++ -Wl,-soname,libmedia.so -shared --sysroot=/home/pro/android-ndk-r9c/platforms/android-9/arch-arm ./obj/local/armeabi/objs/media/P_Decoding.o ./obj/local/armeabi/objs/media/P_Encoding.o jni/libavformat.a jni/libavcodec.a jni/libavutil.a jni/libswscale.a -lgcc ./obj/local/armeabi/libgnustl_shared.so -gcc-toolchain /home/pro/android-ndk-r9c/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86 -no-canonical-prefixes -target armv5te-none-linux-androideabi -Wl,--no-undefined -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now -L/home/pro/android-ndk-r9c/platforms/android-9/arch-arm/usr/lib -llog -ljnigraphics -lz -ldl -lgcc /home/pro/android-ndk-r9c/sources/cxx-stl/gnu-libstdc++/4.8/libs/armeabi/libsupc++.a -lc -lm -o ./obj/local/armeabi/libmedia.so
jni/P_Decoding.cpp:10: error: undefined reference to 'avcodec_register_all'
jni/P_Decoding.cpp:17: error: undefined reference to 'avcodec_find_decoder'
jni/P_Decoding.cpp:14: error: undefined reference to 'avcodec_find_decoder_by_name'
jni/P_Decoding.cpp:24: error: undefined reference to 'avcodec_alloc_context3'
jni/P_Decoding.cpp:50: error: undefined reference to 'avcodec_open2'
jni/P_Decoding.cpp:56: error: undefined reference to 'avcodec_alloc_frame'
jni/P_Decoding.cpp:76: error: undefined reference to 'sws_getContext'
jni/P_Decoding.cpp:90: error: undefined reference to 'avcodec_decode_video2'
jni/P_Decoding.cpp:104: error: undefined reference to 'sws_scale'
jni/P_Decoding.cpp:118: error: undefined reference to 'avcodec_close'
Any help please. Thanks in advance
回答1:
Make sure you have added the extern "C" block around the include of the libavcodec and swscale headers, e.g. like this:
extern "C" {
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
}
See https://libav.org/faq.html#I_0027m-using-Libav-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e for documentation that explains this.
EDIT: Also, are you sure that the prebuilt libavcodec.a is for the same architecture (armeabi-v7a) as you're building? If you are building your shared library for multiple architectures (armeabi-v7a, x86, etc) you need to have multiple corresponding versions of the prebuilt libraries as well.
回答2:
Try ndk-build V=1 to see the actual command that links your library. You want to end up with
-lavformat -lavcodec -lavfilter -lavutil -lswscale
in that order (as here), but I am not sure where avresample swresample x264 should fit. Rearrange your LOCAL_STATIC_LIBRARIES accordingly.
来源：https://stackoverflow.com/questions/27519462/undefined-reference-error-can-not-create-shared-library