Recherche avancée

Sur d’autres sites (6635)

• Problems about c# uses the VideoWriter class in dynamic link libraries(c++ and opencv) [closed]

  11 mai 2023, par Paul_Dx

  error : (-5:Bad argument) CAP_IMAGES : can't find starting number (in the name of file) : in function 'cv::icvExtractPattern'.

  


  I used c++ and opencv to implement the video recording function, and then generated the code to dynamically link libraries for c# to call.But when I run the code, I get an error.

  


  I have a general understanding that opencv calls the ffmpeg package(because of the videowriter class), so I import opencv_videoio_ffmpeg470_64.dll into the project.But the problem was not solved.




  


• ffmpeg continuous live streaming of dynamic files from directory

  4 septembre 2022, par user72261

  So I have been using ffmpeg to create a live stream from files stored in a folder using concat list.

  


  This works perfectly for local, static content but I have a security system in my warehouse that uploads .mp4 files to my server in the office.

  


  This system doesn't have any live stream functionality so I would like to set up a live stream myself using ffmpeg to continually read the latest files from the folder.

  


  I tried setting up a script to read all files in the directory and sort them based on the file name that is a UNIX timestamp of the date/time the video was taken. Then had the script select the latest segments after that last used segment and create a new concat list such as below

  


  file '00000.mpd'
file '00001.mp4'
file '00002.mp4'
file '00003.mp4'
file '00004.mp4'


  


  After doing some reading I found out to make it loop that file you could reference its self in the list like so

  


  file '00000.mpd'
file '00001.mp4'
file '00002.mp4'
file '00003.mp4'
file '00004.mp4'
file 'concat.txt'


  


  This seemed to work ok until I started getting the error impossible to open concat.txt. This file doesn't exist, which I can only guess is because ffmpeg is trying to open the file as its being updated by the script.

  


  Has anyone come across this before or know another way to do it ?

  


• Fastest way to extract moving dynamic crop from video using ffmpeg

  5 avril 2024, par NateW

  I'm working on an AI project that involves object detection and action recognition on roughly 30 minute videos.

  


  My pipeline is the following :

  


  

  • determine crops using object detection model

  


  • extract crops using Python and write them to disk as individual images for each frame.

  


  • use action recognition model by inputting a series of the crops.

  


  


  The models are fast but actual writing of the crops to disk is slow. Sure, using an SSD would speed it up but I'm sure ffmpeg would greatly speed it up.

  


  Some of the challenges with the crops :

  


  

  • the output size is always 128x128

  


  • the input size is variable

  


  • the crop moves on every frame

  


  


  My process for extracting crops is simple using cv2.imwrite(output_crop_path, crop) in a for loop.

  


  I've done experiments trying to use sndcommand and filter_complex. I tried this https://stackoverflow.com/a/67508233/4447761 but it outputs an image with black below the crop and the image gets wrapped around on the x axis.