Question

尝试了很多方法来解决问题，但没有运气。这是我的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)

在jni文件夹中，有与makefile上的.cpp文件相关的所有头文件.hpp文件，还有所有静态.a库和＆＃34; include＆＃34;所有与静态库相关的头文件所在的文件夹。我使用的是ndk9c版本。以下是错误日志的一部分：

[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，现在-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'

请帮忙。提前致谢

Answer 1

确保在libavcodec和swscale标头的包含周围添加了extern "C"块，例如：像这样：

extern "C" {
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
}

有关解释此问题的文档，请参阅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。

编辑：另外，你确定预建的libavcodec.a适用于你正在构建的相同架构（armeabi-v7a）吗？如果要为多个体系结构（armeabi-v7a，x86等）构建共享库，则还需要具有多个相应版本的预构建库。

Answer 2

尝试ndk-build V=1查看链接库的实际命令。你想最终得到

-lavformat -lavcodec -lavfilter -lavutil -lswscale

按此顺序（作为 here ），但我不确定avresample swresample x264应该适合哪个地方。相应地重新排列 LOCAL_STATIC_LIBRARIES 。

未定义的引用错误，无法创建共享库

2 个答案: