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• Python script doesn't work properly when ran through terminal, but works fine in Jupyter and Visual Studio

  21 octobre 2018, par Ivan Novikov

  I have a script to extract the audio from all video files in a folder.

  The folder with videos is located at : /Users/MyName/Downloads/Video_Audio_files

  When I try to run it through terminal and I’m prompted for the folder path folder = input("Path to folder:"), I drag and drop it there (which is how I got the above path), but the script doesn’t seem to be working (stuck at 0 out of 7 and no output files).

  When I input exactly the same path when prompted in Jupyter Notebook or in Visual Studio it works perfectly !

  Edit : I think I have found the issue, when I drag and drop the folder, there is an extra space (’Downloads/folder ’ instead of ’Downloads/folder’).

  pbar = ProgressBar()
  
  files = []
  
  extensions = []
  
  folder = input("Path to folder:")
  
  #folder = 'Video_Audio_files'
  
  pathlist = Path(folder).glob('**/*.mp4')
  
  for path in pathlist:
  
      path_in_str = str(path)
  
      name = path_in_str.split("/")[1]
  
      files.append(path_in_str.split(".")[0])
  
      extensions.append(path_in_str.split(".")[1])
  
  
  
  os.system('cd ' + folder)
  
  
  
  for i in pbar(range(len(files))):
  
      video_format = extensions[i]
  
      video_name = files[i]
  
      output_format = 'flac'
  
      output_name = video_name + '_audio'
  
  
  
      bashCommand = 'ffmpeg -i ' + video_name + '.'   + video_format + ' -f ' + output_format + ' -ab 192000 -vn ' + output_name + '.' + output_format
  
  #should be of this format: bashCommand = 'ffmpeg -i Video.mp4 -f flac -ab 192000 -vn ExtractedAudio.flac'
  
  
  
      os.system(bashCommand)

• Decoding with FFMPEG on Visual Studio 2010

  20 décembre 2018, par user2439801

  I just started using FFMPEG with C++ and try to code an audio decoder then write the decoded audio into a file.

  However i’m not sure about which data to write to the output file. As far as i know from looking at the sample codes it seems to be the AVFrame -> data[0].
  But when i try to print it on the consoles, i get some random numbers that are different each time i run the program. And when i try to write this AVFrame->data[0] into a file i keep getting an error.

  So my question is how can I write the decoded audio after I call the function av_codec_decode_audio4 ?

  Below I attached my code and I pass the argument "C :\02.mp3" which is a path for a valid mp3 file on my PC.

  Thank you for your help.

  // TestFFMPEG.cpp : Audio Decoder
  
  //
  
  
  
  #include "stdafx.h"
  
  
  
  #include <iostream>
  
  #include <fstream>
  
  #include <sstream>
  
  
  
  extern "C" {
  
      #include 
  
      #include 
  
      #include 
  
  
  
  }
  
  
  
  using namespace std;
  
  
  
  
  
  int main(int argc, char* argv[])
  
  {
  
  int audioStream = -1;
  
  
  
  AVCodec         *aCodec;
  
  AVPacket        avPkt;
  
  AVFrame         *decode_frame = avcodec_alloc_frame();
  
  
  
  AVCodecContext  *aCodecCtxt;
  
  AVFormatContext *pFormatCtxt = NULL;
  
  
  
  if(argc != 2) {     // Checking  whether there is enough argument
  
      return -1; 
  
  }
  
  
  
  av_register_all();  //Initialize CODEC
  
  avformat_network_init();
  
  av_init_packet (&amp;avPkt);
  
  
  
  
  
   if (avformat_open_input (&amp;pFormatCtxt, argv[1],NULL,NULL)!= 0 ){ //Opening File
  
       return -2;
  
   }
  
  
  
   if(avformat_find_stream_info (pFormatCtxt,NULL) &lt; 0){ //Get Streams Info 
  
       return -3; 
  
   }
  
  
  
   AVStream *stream = NULL;
  
   //av_read_play (pFormatCtxt); //open streams
  
  
  
  
  
   for (int i = 0;  i &lt; pFormatCtxt->nb_streams ; i++) { //Find Audio Stream
  
       if (pFormatCtxt->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO){
  
           audioStream =i;
  
       }
  
   }
  
  
  
   aCodecCtxt = pFormatCtxt ->streams [audioStream]->codec; // opening decoder   
  
   aCodec = avcodec_find_decoder( pFormatCtxt->streams [audioStream] ->codec->codec_id);
  
  
  
   if (!aCodec) {
  
       return -8;
  
   }
  
  
  
   if (avcodec_open2(aCodecCtxt,aCodec,NULL)!=0) {
  
       return -9; 
  
   } 
  
  
  
  int cnt = 0;
  
  
  
  while(av_read_frame(pFormatCtxt,&amp;avPkt) >= 0 ){
  
  
  
      if (avPkt.stream_index == audioStream){
  
          int check = 0; 
  
          int result = avcodec_decode_audio4 (aCodecCtxt,decode_frame,&amp;check, &amp;avPkt);
  
          cout &lt;&lt; "Decoded : "&lt;&lt; (int) decode_frame->data[0] &lt;&lt;", "&lt;&lt; "Check : " &lt;&lt; check &lt;&lt; ", Format :" &lt;&lt; decode_frame->format &lt;&lt;" " &lt;&lt; decode_frame->linesize[0]&lt;&lt; " "&lt;<cnt return="return" acodec="acodec">id;  
  
  } 
  
  </cnt></sstream></fstream></iostream>

• Adding FFmpeg library as dependency in Visual studio project to get rid of LNK2019 error

  13 mars 2019, par MSD Paul

  While compiling a project on Microsoft visual studio (to generate dll), I am getting the following linking errors (LNK2019)

  Severity Code Description Project File Line Suppression State
  Error LNK2019 unresolved external symbol av_strerror referenced in function "private : void __cdecl DecoderFFmpeg::printErrorMsg(int)" (?printErrorMsg@DecoderFFmpeg@@AEAAXH@Z)
  Severity Code Description Project File Line Suppression State
  Error LNK2019 unresolved external symbol av_get_channel_layout_nb_channels referenced in function "private : int __cdecl DecoderFFmpeg::initSwrContext(void)"

  several other functions like av_dict_set, av_dict_free, avcodec_decode2 which is related to the ffmpeg libraries. Can anyone please tell me how to properly add "ffmpeg" as dependenciesto this project and link it properly ?