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• Simultaneously map video and data streams to one subprocess pipeline in real-time

  9 février 2023, par seabass1217

  I need to process the video stream and the klvdata streams simultaneously in real-time in OpenCV/Python. I'm using FFMPEG to read the file or stream as OpenCV does not retain the klvdata. I pass the data to OpenCV with the subprocess module.

  


  My problem is I cannot figure out how to map both the video and klvdata to the same subprocess pipe simultaneously ?

  


  My code :

  


  #!/usr/bin/env python3
import sys, json, klvdata;
from subprocess import PIPE
import subprocess as sp
import cv2
import numpy

command = ['ffmpeg',
    '-i', 'DayFlight.mpg',
    '-map', '0:0',
    '-map', '0:d',        
    '-pix_fmt', 'bgr24',
    '-c:v', 'rawvideo',      
    '-an','-sn',              
    '-f', 'image2pipe', '-',
    '-c:d', 'copy',
    '-f','data',
    ]

pipe = sp.Popen(command, stdin=sp.PIPE, stdout=sp.PIPE, stderr=sp.PIPE, bufsize=10**8)

while True:
   raw_image = pipe.stdout.read(1280*720*3)
   image =  numpy.fromstring(raw_image, dtype='uint8')
   image = image.reshape((720,1280,3))          
   if image is not None:
      cv2.imshow('Video', image)
   if cv2.waitKey(1) & 0xFF == ord('q'):
      break
   for packet in klvdata.StreamParser(pipe.stdout): 
      metadata = packet.MetadataList()
      print(metadata)
pipe.stdout.flush()
cv2.destroyAllWindows()



  


  Produces the below error :

  


  Traceback (most recent call last):&#xA;  File "test_cv.py", line 32, in <module>&#xA;    metadata = packet.MetadataList()&#xA;AttributeError: &#x27;UnknownElement&#x27; object has no attribute &#x27;MetadataList&#x27;&#xA;&#xA;</module>

  


  Any help is greatly appreciated.

  


• How can i crop part of a video while recording from desktop in real time using ffmpeg ? [on hold]

  28 juillet 2017, par daniel llee

  I’m using this line to record from the desktop to a video file :

  ffmpeg -f gdigrab -framerate 24 -i desktop -preset ultrafast -pix_fmt yuv420p out.mp4

  But this will record the whole desktop. Is there any way to record in real time only specific area/part of the desktop ?

  And this is how i’m using the ffmpeg with winforms :

  using System;  
  
  using System.Collections.Generic;  
  
  using System.Linq;  
  
  using System.Text;  
  
  using System.Threading.Tasks;  
  
  using System.IO;  
  
  using System.Diagnostics;  
  
  
  
  namespace Ffmpeg_App  
  
  {  
  
      class Ffmpeg  
  
      {  
  
          Process process;  
  
  
  
          public void Start(string FileName, int Framerate)  
  
          {  
  
              process = new System.Diagnostics.Process();  
  
              process.StartInfo.FileName = @"D:\ffmpegx86\ffmpeg.exe"; // Change the directory where ffmpeg.exe is.  
  
              process.EnableRaisingEvents = false;  
  
              process.StartInfo.WorkingDirectory = @"D:\ffmpegx86"; // The output directory  
  
              process.StartInfo.Arguments = @"-f gdigrab -framerate " + Framerate + " -i desktop -preset ultrafast -                                                                     pix_fmt yuv420p " + FileName;  
  
              process.Start();  
  
              process.StartInfo.UseShellExecute = false;  
  
              process.StartInfo.CreateNoWindow = false;  
  
              Close();  
  
          }  
  
  
  
          public void Close()  
  
          {  
  
              process.Close();  
  
          }  
  
      }  
  
  }  

• How video editor show real time preview of videos ? [closed]

  3 juin 2024, par SWIK

  I am trying to create a simple video editor that combine two video by layering one over another, i can easily do it with ffmpeg, but I am not sure how can I make a preview of it before making final video ? How video editor display preview without building them ? I am looking towards create a react application.