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• How to create effect same video with FFmpeg

  29 juin 2023, par Sang Vo

  How to make a video from an image with a drag effect like this one in FFmpeg :

  


  https://www.youtube.com/watch?v=zC6qbpe3FyE&ab_channel=CloudMood


  


  I tried to zoom in zoom out effects but not the same with video

  


   ffmpeg -loop 1 -i photo.jpg -vf "zoompan=z='min(zoom+0.001,1.2)':x='if(gte(zoom,1.2),x+2,x-1)':y='if(gte(zoom,1.2),y+2,y-1)':d=10*25,framerate=25,scale=1920:1080" -c:v libx264 -t 10 -pix_fmt yuv420p -s 1920x1080 output.mp4


  


• FFmpeg avutil.lib unresolved external symbol

  2 août 2022, par Sere

  i'm trying to use FFmpeg with visual sudio 2022 .NET 6 through an MSVC project.
I followed this tutorial : https://www.youtube.com/watch?v=qMNr1Su-nR8&ab_channel=HakanSoyalp.
I mean I have configureg Include (.h) file, library (.lib) files and dynamic (.dll) file copied into bin folder.
If I call for example the avformat_alloc_context() method inside the avformat.lib all work rightly, if I call for example av_file_map(...) inside the avutil.lib the compiler give me an error :
LNK2019 unresolved external symbol "int __cdecl av_file_map ...
But the avutil.lib is linked !!!
The same happen if I call other methods inside avutil.lib module.

  


  Thanks for help...

  


  Code :

  


  extern "C"&#xA;{&#xA;    #include <libavformat></libavformat>avformat.h>&#xA;    #include <libavutil></libavutil>file.h> // av_file_map&#xA;}&#xA;&#xA;int ConvertJPEGtoNALs(int argc, char* argv[])&#xA;{&#xA;    AVFormatContext* fmt_ctx = NULL;&#xA;    AVIOContext* avio_ctx = NULL;&#xA;    uint8_t* buffer = NULL, * avio_ctx_buffer = NULL;&#xA;    size_t buffer_size, avio_ctx_buffer_size = 4096;&#xA;    char* input_filename = NULL;&#xA;    int ret = 0;&#xA;    struct buffer_data bd = { 0 };&#xA;    if (argc != 2) {&#xA;        fprintf(stderr, "usage: %s input_file\n"&#xA;            "API example program to show how to read from a custom buffer "&#xA;            "accessed through AVIOContext.\n", argv[0]);&#xA;        return 1;&#xA;    }&#xA;    input_filename = argv[1];&#xA;    /* register codecs and formats and other lavf/lavc components*/&#xA;    //av_register_all();    //!deprecated&#xA;    /* slurp file content into buffer */&#xA;    ret = av_file_map(input_filename, &amp;buffer, &amp;buffer_size, 0, NULL);&#xA;    /* fill opaque structure used by the AVIOContext read callback */&#xA;    bd.ptr = buffer;&#xA;    bd.size = buffer_size; ???&#xA;    if (!(fmt_ctx = avformat_alloc_context())) {&#xA;        ret = AVERROR(ENOMEM);&#xA;        goto end;&#xA;    }&#xA;    //... to be continue ...&#xA;}&#xA;

  


• OpenCV Python, reading video from named-pipe

  29 février 2020, par BlueNut

  I am trying to achieve results as shown on the video (Method 3 using netcat) https://www.youtube.com/watch?v=sYGdge3T30o
  It is to stream video from raspberry pi to PC and process it using openCV and python.

  I use command

  raspivid -vf -n -w 640 -h 480 -o - -t 0 -b 2000000 | nc 192.168.1.137 8000

  to stream the video to my PC and then on the PC I created name pipe ’fifo’ and redirected the output

  nc -l -p 8000 -v > fifo

  then i am trying to read the pipe and display the result in the python script

  import cv2
  
  import subprocess as sp
  
  import numpy
  
  
  
  FFMPEG_BIN = "ffmpeg.exe"
  
  command = [ FFMPEG_BIN,
  
          '-i', 'fifo',             # fifo is the named pipe
  
          '-pix_fmt', 'bgr24',      # opencv requires bgr24 pixel format.
  
          '-vcodec', 'rawvideo',
  
          '-an','-sn',              # we want to disable audio processing (there is no audio)
  
          '-f', 'image2pipe', '-']    
  
  pipe = sp.Popen(command, stdout = sp.PIPE, bufsize=10**8)
  
  
  
  while True:
  
      # Capture frame-by-frame
  
      raw_image = pipe.stdout.read(640*480*3)
  
      # transform the byte read into a numpy array
  
      image =  numpy.frombuffer(raw_image, dtype='uint8')
  
      image = image.reshape((480,640,3))          # Notice how height is specified first and then width
  
      if image is not None:
  
          cv2.imshow('Video', image)
  
  
  
      if cv2.waitKey(1) & 0xFF == ord('q'):
  
          break
  
      pipe.stdout.flush()
  
  
  
  cv2.destroyAllWindows()

  But I got this error :

  Traceback (most recent call last):
  
    File "C:\Users\Nick\Desktop\python video stream\stream.py", line 19, in <module>
  
      image = image.reshape((480,640,3))          # Notice how height is specified first and then width
  
  ValueError: cannot reshape array of size 0 into shape (480,640,3)
  
  </module>

  It seems that the numpy array is empty, so any ideas to fix this ?