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• c# using pipes to get output stream

  1er janvier 2017, par lilscarecrow

  I am trying to pipe youtube-dl output to ffmpeg as input, but cannot seem to get the piping part to work. In normal cmd, I can do something like

   C:\YT\youtube-dl.exe -o - https://www.youtube.com/watch?v=L4aLQ0ki9Tk | ffmpeg -i pipe:0 -f asf pipe:1 

  but in c# this doesn’t work. Currently, I have c# create 2 processes :

  one for youtube-dl

  C:\YT\youtube-dl.exe -o - https://www.youtube.com/watch?v=L4aLQ0ki9Tk

  and another for ffmpeg

  ffmpeg  -i {yt.StandardOutput} -f s16le -ar 48000 -ac 2 pipe:1

  The problem is with the {yt.StandardOutput} (where yt is the process name of the youtube-dl process and -i specifies the input file/stream). Using pipe:0 doesn’t work either and I am not sure how to link the piped output of the first to the input of the second.

• Reading encoded videos produces different result [closed]

  10 août 2024, par Mike

  I'm attempting to losslessly encode video using ffmpeg, using the x265 parameter lossless=1. I pipe the input mp4 in rawvideo format, and pipe it back to std write, so hypothetically the same video with the same RGB values should then be encoded in this output video. However, when I pipe my output video and read each frame's values, they are oftentimes significantly different. Why is this happening ? Is this just a result of the compression even though I'm specifying lossless=1 ? Sometimes the values can differ significantly, e.g. by .04.

  


• 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.