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• clang++ : error : linker command failed with exit code 1 (use -v to see invocation) [duplicate]

  1er avril 2020, par Pradeep Simba

  When I build ndk with ffmpeg it occurs error.

  



  

  



  Android.mk file

  



  LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_C_INCLUDES += ./include
LOCAL_MODULE     := native-lib
LOCAL_CFLAGS := -DSTDC_HEADERS -std=c99
LOCAL_CFLAGS := -Wno-pointer-sign
LOCAL_ARM_MODE := arm
APP_OPTIM := release
LOCAL_SRC_FILES  := \
./native-lib.cpp
LOCAL_LDLIBS := -llog
include $(BUILD_SHARED_LIBRARY)


  



  native-lib.cpp file

  



  #include &#xA;#include <string>&#xA;&#xA;extern "C"&#xA;{&#xA;#include "libavcodec/avcodec.h"&#xA;#include "libavformat/avformat.h"&#xA;#include "libavutil/opt.h"&#xA;}&#xA;&#xA;extern "C" JNIEXPORT jstring JNICALL&#xA;Java_com_example_m_MainActivity_stringFromJNI(&#xA;    JNIEnv* env,&#xA;    jobject /* this */) {&#xA;std::string hello = "Hello from C&#x2B;&#x2B;";&#xA;av_register_all();&#xA;return env->NewStringUTF(hello.c_str());&#xA;}&#xA;</string>

  



  When I build ndk this error occurs.

  



  

  



  D:\Github\n>ndk-build
Android NDK: APP_PLATFORM not set. Defaulting to minimum supported version android-16.
[arm64-v8a] Compile++      : native-lib <= native-lib.cpp
[arm64-v8a] SharedLibrary  : libnative-lib.so
./obj/local/arm64-v8a/objs/native-lib/./libmp3lame/native-lib.o: In function `Java_com_example_m_MainActivity_stringFromJNI':
D:\Github\n/jni/./libmp3lame/native-lib.cpp:16: undefined reference to `av_register_all'
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [D:/install/sdk/ndk/21.0.6113669/build//../build/core/build-binary.mk:725: obj/local/arm64-v8a/libnative-lib.so] Error 1

D:\Github\n>ndk-build -v
GNU Make 4.2.1
Built for x86_64-w64-mingw32
Copyright (C) 1988-2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later /gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

D:\Github\n>


  



  why it comes like this native-lib.cpp:16: undefined reference av_register_all ?

  



  I added all the required libs in my jni folder . but, why this error and this native-lib.cpp:16 : undefined reference av_register_all comes ?

  



  How can I solve this ?

  


• Efficient and Perfect way to extract frames from a large size video using python or ffmpeg according the timecode given

  5 avril 2020, par Yong En

  let's say I have a video from youtube with at least 600 MB. The video is used for annotation where I have the annotated information in another text file. The annotation file has the timecode in millisecond (SSSS.ss). What I am trying to do is going into the timecode on the video and getting out the frames within the this period (TWO timecodes). There are TWO approaches that I used with different tools, one is using openCV in python and FFmpeg in bash script :

  



  I would stick with few variables here,

  



  

  • fps = 25

  


  • timecode (after convert into second) = 333.44 to 334.00 take note that I am dealing with time period that might less than a second.

  


  



  openCV

  



  

  1. Using openCV in python, I read the video into frame by frame. Ends up with a numpy array.

  


  2. Using the fps from video, eg. fps = 25. I can estimate where does the frames that fall under this time period which give me what I want.

  


  3. Problem here is I will missed out some frames here due to the video fps is not really 25 as given by the video misinformation, it could 24.xx. Any solutions ?

  


  



  ffmpeg

  



  

  1. What I did, every time I want to get the frames, I run the script.

  


  2. Problem here is I need to read the video 100 times if I have 100 time periods. Any ways to overcome this ?

  


  



  Thanks for reading it.

  


• clang++ : error : linker command failed with exit code 1 (use -v to see invocation) in cpp with ffmpeg

  6 avril 2020, par Pradeep Simba

  clang++: error: linker command failed with exit code 1 (use -v to see invocation)


  



  I saw this link and link2. But, it not done.

  



  My jni folder :

  



  

  



  Android.mk file

  



  LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_C_INCLUDES += ./include
LOCAL_MODULE     := native-lib
LOCAL_CFLAGS := -DSTDC_HEADERS -std=c99
LOCAL_CFLAGS := -Wno-pointer-sign
LOCAL_ARM_MODE := arm
APP_OPTIM := release
LOCAL_SRC_FILES  := \
./native-lib.cpp
LOCAL_LDLIBS := -llog
include $(BUILD_SHARED_LIBRARY)


  



  native-lib.cpp file

  



  #include &#xA;#include <string>&#xA;&#xA;extern "C"&#xA;{&#xA;#include "libavcodec/avcodec.h"&#xA;#include "libavformat/avformat.h"&#xA;#include "libavutil/opt.h"&#xA;}&#xA;&#xA;extern "C" JNIEXPORT jstring JNICALL&#xA;Java_com_example_m_MainActivity_stringFromJNI(&#xA;JNIEnv* env,&#xA;jobject /* this */) {&#xA;std::string hello = "Hello from C&#x2B;&#x2B;";&#xA;av_register_all();&#xA;return env->NewStringUTF(hello.c_str());&#xA;}&#xA;</string>

  



  When I build ndk this error occurs.

  



  D:\Github\n>ndk-build
Android NDK: APP_PLATFORM not set. Defaulting to minimum supported version android-16.
[arm64-v8a] Compile++      : native-lib <= native-lib.cpp
[arm64-v8a] SharedLibrary  : libnative-lib.so
./obj/local/arm64-v8a/objs/native-lib/./libmp3lame/native-lib.o: In function `Java_com_example_m_MainActivity_stringFromJNI':
D:\Github\n/jni/./libmp3lame/native-lib.cpp:16: undefined reference to `av_register_all'
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [D:/install/sdk/ndk/21.0.6113669/build//../build/core/build-binary.mk:725: obj/local/arm64-v8a/libnative-lib.so] Error 1

D:\Github\n>ndk-build -v
GNU Make 4.2.1
Built for x86_64-w64-mingw32
Copyright (C) 1988-2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later /gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

D:\Github\n>


  



  why it comes like this native-lib.cpp:16: undefined reference av_register_all ?

  



  I added all the required libs in my jni folder but, why this error and this native-lib.cpp:16: undefined reference av_register_all comes ?
How can I solve this ?