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• Python librosa NoBackendError even though ffmpeg is installed

  11 avril 2020, par Slavko Kovačević

  I recently installed librosa (package I've been using for a while on different PC) on my new PC with Windows 10 running. After that I've downloaded latest static version of ffmpeg and copied it to C: and added it to the Path. Tested ffmpeg and it works like a charm ! For python I am using Anaconda environment and after starting Jupyter Notebook and running librosa.load(path, sr = None) I've got

  



   in <module>&#xA;----> 1 audio = librosa.load(pathToJson)&#xA;&#xA;~\anaconda3\envs\tf_gpu\lib\site-packages\librosa\core\audio.py in load(path, sr, mono, offset, duration, dtype, res_type)&#xA;    117 &#xA;    118     y = []&#xA;--> 119     with audioread.audio_open(os.path.realpath(path)) as input_file:&#xA;    120         sr_native = input_file.samplerate&#xA;    121         n_channels = input_file.channels&#xA;&#xA;~\anaconda3\envs\tf_gpu\lib\site-packages\audioread\__init__.py in audio_open(path, backends)&#xA;    114 &#xA;    115     # All backends failed!&#xA;--> 116     raise NoBackendError()&#xA;&#xA;NoBackendError:&#xA;</module>

  



  strange isn't it ? Then I went all over the internet, doing whatnot trying to fix it and then I've got an idea to run my line of code inside anaconda command interface and it WORKS ?? How is this possible ? It is the same environment.

  



  python
Python 3.7.7 (default, Mar 23 2020, 23:19:08) [MSC v.1916 64 bit (AMD64)] :: Anaconda, Inc. on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import librosa
>>> librosa.load('test.wav')
(array([-0.00027   , -0.00039953, -0.0003659 , ..., -0.16393574,
       -0.17814247,  0.        ], dtype=float32), 22050)


  



  I did a lot of testing and I really prefer my Jupyter so any help would be appreciated. I tried the following : I've added C:\ffmpeg\bin and C:\ffmpeg to my Path for both User and System Variables. After that I've made specific variables for ffmpeg and ffmpeg_bin for both User and System Variables. No luck. After that I've tried installing ffmpeg using conda, without success. The last thing I've tested is this :

  



  import audioread
audioread.ffdec.FFmpegAudioFile('test.wav')


  



  and that works. Thanks

  


• Using ffmepg wrapper to convert images to movie file

  24 mai 2020, par reborn

  I have recently been using the ffmpeg wrapper by Vitaliy Fedorchenko called NReco.VideoConverter. It's pretty great and I have managed to write another application with it that I hope to release soon after some testing and I purchase the license for the wrapper (it's a cool watermarker for videos).

  



  I am now trying to use that same wrapper to encode a video from still images, but sadly there is very little documentation available and I am feeling my way int he dark a little. I am hopeful that someone familiar with the wrapper might be able to help.

  



  I collect the images using the fileOpenDialogue and picking images to populate a listView. When I am ready, I then take these images to build an array and create the movie.

  



  application picture

  



      void ConvertToMovie()
    {
        if(listImages.Items.Count > 1)
        {
            var ffMpeg = new NReco.VideoConverter.FFMpegConverter();

            NReco.VideoConverter.FFMpegInput[] ffMpegInputs = new NReco.VideoConverter.FFMpegInput[listImages.Items.Count]; 

            for (int i = 0; i < listImages.Items.Count; i++)
            {
                var SSAImage = new NReco.VideoConverter.FFMpegInput(listImages.Items[i].SubItems[2].Text.ToString());
                ffMpegInputs[i] = SSAImage;
            }


            ConvertSettings csettings = new ConvertSettings();
            csettings.SetVideoFrameSize((int)MovieWidth.Value, (int)MovieHeight.Value);
            csettings.VideoFrameCount = listImages.Items.Count;
            csettings.VideoFrameRate = (int)FPS.Value;

            /*
            string argument = " -profile:v high ";
            csettings.CustomOutputArgs = argument;
            */

            if (FormatChooser.SelectedIndex == 0)
            {
                //This just takes the first picture and converts that single frame into a movie.
                ffMpeg.ConvertMedia(ffMpegInputs, @"Converted.avi", Format.avi, csettings);
                //ffMpeg.ConvertMedia(listImages.Items[0].SubItems[2].Text.ToString(), ffMpegInput.Format, @"Converted.avi", Format.avi, csettings);
            }
        }
        else
        {
            MessageBox.Show("You need at least two images to make a movie.", Title);
        }
    }


  



  Passing the images as an array to the function seems logical. At list of the methods are here : https://www.nrecosite.com/doc/NReco.VideoConverter/

  



  However, the only method that allows you to pass an array of the inputs is here :
https://www.nrecosite.com/doc/NReco.VideoConverter/html/M_NReco_VideoConverter_FFMpegConverter_ConvertMedia.htm

  



  So this makes sense to me that it would be the one to use.

  



  This does generate a .avi file, but the movie only contains the first frame from the array.

  



  I saw someone else had the same issue here : Nreco video converter make video from image sequence

  



  However, the responses seemed to suggest using a different method that allows you to pass a single image file only, then somehow the ffmpeg.exe will sequence the rest of them ? I couldn't get that to work at all.

  



  At this stage the only way I can see of making it work is creating a single frame movie file for each frame, and then concating all of the movie files together using :

  



  https://www.nrecosite.com/doc/NReco.VideoConverter/?topic=html/M_NReco_VideoConverter_FFMpegConverter_ConcatMedia.htm

  



  That's a pretty ridiculous notion though.

  


• 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 ?