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• Detect and crop image of a screen using Python

  19 janvier 2023, par brenodacosta

  I am trying to extract the image that is present in the screen of a TV (or a generic display). My first thought was to use YOLO, but this doesn't look very efficient, since YOLO detects a TV, but not the screen itself :

  


  I wanted to have the red bounding box, while YOLO can only give me the orange one :

  


  

  


  Is there way that do that using Python (or any framework that I could look for) ? I've searched for while, but I haven't found anything useful, I only get ambiguous results as how to detect objects in a given display, rather then how detect that a screen is present in an image

  


• 4K Screen Recording on 1080p Monitors [closed]

  10 avril, par Souhail Benlhachemi

  I have created a basic windows screen recording app (ffmpeg + GUI), but I noticed that the quality of the recording depends on the monitor used to record, the video recording quality when recorded using a full HD is different from he video recording quality when recorded using a 4k monitor (which is obvious).

  


  There is not much difference between the two when playing the recorded video with a scale of 100%, but when I zoom to 150% or more, we clearly can see the difference between the two recorded videos (1920x1080 VS the 4k).

  


  I did some research on how to do screen recording with a 4k quality on a full hd monitor, and here is what I found :

  


  I played with the windows duplicate API (AcquireNextFrame function which gives you the next frame on the swap chain), I successfully managed to convert the buffer to a PNG image and save it locally to my machine, but as you expect the quality was the same as a normal screenshot ! Because AcquireNextFrame return a frame after it is rasterized.

  


  Then I came across what’s called “Graphics pipeline”, I spent some time to understand the basics, and finally I came to a conclusion that I need to intercept somehow the pre-rasterize data (the data that comes before the Rasterizer Stage - Geometry shaders, etc...) and then duplicate this data and do an off-screen render on a new 4k render target, but the windows API don’t allow that, there is no way to do that ! The only option they have on docs is what’s called Stream Output Stage, but this is useful only if you want to render your own shaders, not the ones that my display is using. (I tried to use MinHook to intercept data but no luck).

  


  After that, I tried a different approach, I managed to create a virtual display as extended monitor with 4k resolution, and record it using ffmpeg, but as you know what I’m seeing on my main display on my monitor is different from the virtual display (only an empty desktop), what I need to do is drag and drop app windows using my mouse to that screen manually, but this will put us in a problem when recording, we are not seeing what we are recording xD.

  


  I found some YouTube videos that talk about DSR (Dynamic Super Resolution), I tried that on my nvidia control panel (manually with GUI) and it works. I managed to fake the system that I have a 4k monitor and the quality of the recording was crystal clear. But I didn’t find anyway to do that programmatically using NVAPI + there is no API for that on AMD.

  


  Has anyone worked on a similar project ? Or know a similar project that I can use as reference ?

  


  suggestions ?

  


• avdevice/x11grab : fix cursor drawing in multi-screen setup

  8 septembre 2014, par Antonio Ospite

  avdevice/x11grab : fix cursor drawing in multi-screen setup
  The code uses XFixes to retrieve the cursor coordinates, but XFixes
  
  gives no information of what screen the pointer is on ; this results in
  
  always drawing the cursor on the captured screen even if the mouse
  
  pointer was on another screen.
  For example, when capturing from screen 1 (i.e. -f x11grab -i ":0.1")
  
  the cursor was being drawn in the captured image even when the mouse
  
  pointer was actually on screen 0, which is wrong and visually confusing.
  Use XQueryPointer to check that the pointer is actually on the screen
  
  which is being captured.
  Signed-off-by : Antonio Ospite <ao2@ao2.it>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavdevice/x11grab.c