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• 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 ?

  


• Stop termux on battery low [closed]

  9 août 2022, par Wouter van Dam

  TL ;DR BELOW

  


  I have a second phone who is converting some mkv files through ffmpeg in termux. But the phone can't get enough charging power from the charger because it uses to much power. So it state is always charging even if it isn't charging. No I want to run in termux a script that hits a kill command when the battery is low. So that it doesn't corrupt my files when shutting down because it just cant survive the night with my battery capacity. Any ideas of achieving this ?

  


  TL ;DR
How to run a termux command or script async with a event or looping function so that it kills the process when battery power is low.

  


• C# Video streaming FFMPEG delay [on hold]

  2 novembre 2014, par user3478490

  I try to develop a C# WinForm program that has mainForm that include the UI.
  on the mainForm is couples of PictureBoxs , each pb need to display a different video stream from web cam type basler.
  I have two problems :
  1) I creating instance of the mainForm for each screen monitor in my pc (For example if I have 2 monitors so 2 mainForm’s instance for each monitor) , the problem is when i using extended desktop and the video is displaying on both forms that cause a HUGE delay in the video thatI dont know how to avoid it, when I using my desktop on duplicate mode (seeing same desktop on 2 monitors) that not cause any delay at all with the video
  2) When I connect more than one camera (2+ , like I said I have couples of pb’s) that cause delay too on each camera also.
  Maybe someone can tell me how to avoid that delay ?
  I using FFMPEG dll’s to display video , record , etc.
  Must fix that delay problem , if some one can help me would be great
  thanks alot !