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• Is there a way to apply a curve bend in ffmpeg ?

  25 mars 2020, par stevendesu

  I have four cameras each feeding me a different portion of a basketball court. Due to the slight offset of the cameras physical locations and lens distortion around the edges of the camera, I cannot simply stitch the videos together without some kind of correction.

  I’ve looked into ffmpeg’s perspective filter, as well as the lenscorrection filter. In the former case it was only able to create a trapezoid, not the curved image I want. In the latter case using negative values to k1 and k2 seemed to be heading in the right direction, but it either disorted the top and bottom of the image to the point of being nonsensical noise, or it zoomed in to the image so much that I lost important details.

  For the sample picture below, ultimately I want the midcourt line (the blue vertical line on the right side) to be vertical, and I want the mess of wires on the white desk at the bottom to remain visible and identifiable.

  Given a video which looks like the following :

  

  I wish to produce something like the following :

  

  This image was made using the "Curve Bend" filter in GIMP, but I just eye-balled it - so it’s not perfect. Ideally once I get the exact parameters the midcourt line will be perfectly vertical

  When using the lenscorrection filter, no values for k1 and k2 seemed to get the effect I want :

  Negative k1, negative k2 :

  

  Negative k1, positive k2 :

  

  Positive k1, negative k2 :

  

  Positive k1, positive k2 :

  

  In general :

  • negative / negative distorted the image beyond recognition
  • negative / positive looked alright, but the midcourt line was off the screen and it wasn’t clear if any distortion had been applied
  • positive / negative looked the best, but while the top and bottom curved in the middle of the left and right actually bulged out, leaving the midcourt line distorted
  • positive / positive was the opposite of the desired effect

• Unity FFmpeg plugin gives "incomplete return type timespec" on xcode build

  22 septembre 2023, par Burak I.

  I am using this plugin in one of my unity project. Android build is working without an error but when I try build it on Ios, it gives errors :

  


  

  


  I couldn't find much information about this issue. I think the problem is caused by FFmpeg library on ios.

  


  How can I fix these errors ?

  


  I tried to delete libavutil library since I am not using it (I think). But resulted in much more errors in other packages.

  


  I found a suggestion to recompile the ffmpeg library but I don't know how to compile it for Unity.

  


  Edit : I found the solution. I know it is caused by libavutil library but I shouldn't delete libavutil from lib folder. I deleted libavutil folder from include. So if anybody encounter with this problem only delete "Assets\FFmpegUnityBind2\Plugins\IOS\include\libavutil" folder. DO NOT DELETE libavutil.a from "IOS\lib\libavutil". I only used FFmpeg for turning jpg sequence to mp4 so be aware if you are doing another process that uses libavutil library.

  


• Opencv VideoCapture not streaming RTSP link and returns "no frame !"

  6 septembre 2023, par Asadullah Naeem

  I am trying to stream my HikVision IP camera throough python. I am using cv2.VideoCapture("rtsp_link") which works fine on my Laptop but when I try to run the same python script with same Opencv and FFmpeg version it gives me following error :

  


  Error :

  


  [h264 @ 000002124c7f9a40] missing picture in access unit with size 47
[h264 @ 000002124c7f9a40] no frame!


  


  I have so far tried to run this script on 5 computer devices but it gives the same error. I am using the following python script and my Opencv version is 4.6.0.66 and ffmpeg version 2022-06-20-git-56419428a8-essentials_build-www.gyan.dev :

  


  Python Script :

  


  import cv2

# RTSP stream URL
rtsp_url = "rtsp://username:password@ip_address:port/Streaming/Channels/501"

# Open the RTSP stream
cap = cv2.VideoCapture(rtsp_url)

# Check if the stream was successfully opened
if not cap.isOpened():
    print("Failed to open RTSP stream.")
    exit()

# Read and display frames from the stream
while True:
    # Read a frame from the stream
    ret, frame = cap.read()

    # Check if the frame was successfully read
    if not ret:
        print("Failed to read frame from RTSP stream.")
        break

    # Display the frame
    cv2.imshow("RTSP Stream", frame)

    # Exit if 'q' is pressed
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# Release the resources
cap.release()
cv2.destroyAllWindows()



  


  Update :

  


  Code runs on a laptop on both wifi and mobile internet (4G) but on other devices rtsp link is accessible only with mobile internet (4G).