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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 ?

  


• How to add subtitles to PowerPoint presentation

  5 septembre 2018, par ppdlx

  Okay, to clear things up I will say that I’m posting here because I found the answer and want to help people in future who come upon the same problem. Since PowerPoint is not the right tool to title an presentation I will tell you my way of doing this. If you can do it in PowerPoint alone, super for you but I could not do it in PowerPoint alone, therefore this way. So what I did is the following, I simply recorded the presentation and made subtitles for it and in the final I hardcoded the subtitles into the video. Here is how I did it.

  How to add subtitles to your PowerPoint presentation

  First, I downloaded the latest SnagIt software from their official website. You can have a free trial there. Click here to download SnagIt. Then using SnagIt I recorded my whole screen and played the presentation. I made a video file of the presentation. Let’s call it presentation.mp4.

  Then I downloaded my subtitle making software, an awesome open source program called Subtitle Edit from it’s official website. It’s really simple to use it and it is awesome and user friendly. It doesn’t take too long to subtitle a three minute presentation. When you are satisfied with the subtitles save them as .srt and call them whatever you like. Now we have a video file and corresponding subtitles for it.

  Now we need to hardcode the subtitles into the video file, in other words to burn the subtitles to the video. I did this using another awesome open source software called ffmpeg. See the website and download it from official ffmpeg website. Extract it somewhere and for convinience put subtitle and video file to it’s bin directory. You can put it elsewhere if you like it that way. The first command I used is to transform .srt to .ass.

  ffmpeg -i subtitles.srt subtitles.ass

  Afterwards it’s easy to make a subtitled video file with the following command :

  ffmpeg -i presentation.mp4 -vf ass=subtitles.ass presentation_subtitled.mp4

  I am not sure for the command and can’t get now to see the correct command but if it fails you can seek help on this page.

  Now that we have our presentation_subtitled.mp4 we can now trim the video to our likings.

  ffmpeg -i presentation_subtitled.mp4 -ss 00:01:00 -to 00:02:00 -c copy presentation_final.mp4

  Of course, edit the -ss and -to option, it’s the start time and the end time of your video.

  That’s it ! Now you have your presentation_final.mp4 video file where you have your presentation with subtitles. Ffmpeg is awesome because you can convert it to any format you like.

  You have some help with hardcoding subtitles on Subtitle Edit web page, but one software gave me a virus, one software didn’t work, and after trial and error this is the way that worked for me and it’s really convinied due to great open source software - Subtitle Edit and ffmpeg.

• How to decrypt hls video content

  16 mai 2019, par SHAH MD MONIRUL ISLAM

  My requirement is to play the encrypted hls video files from local storage in android. I have used NanoHTTPD to create and run the local server. From there I am serving the .ts an .m3u8 files. To play this video ExoPlayer need a key to decrypt the files and thus I made a url : http://localhost:4990/dataKey.

  Here is my local server class :

  import android.os.Environment;
  
  import android.util.Log;
  
  
  
  import java.io.File;
  
  import java.io.FileInputStream;
  
  import java.io.FileNotFoundException;
  
  import java.util.Map;
  
  
  
  import fi.iki.elonen.NanoHTTPD;
  
  
  
  public class LocalStreamingServer extends NanoHTTPD{
  
      public LocalStreamingServer(int port){
  
          super(port);
  
  
  
      }
  
  
  
      @Override
  
      public Response serve(IHTTPSession session){
  
          Log.e("req", session.getUri());
  
  
  
          if(session.getUri().equalsIgnoreCase("/dataKey")){
  
  
  
              return newFixedLengthResponse(Response.Status.OK, "txt", "what is the key?");
  
          }
  
  
  
          if(session.getUri().contains("m3u8")){
  
              String path = Environment.getExternalStorageDirectory().toString() + "/s3" + session.getUri();
  
  
  
              FileInputStream fis = null;
  
              File f = new File(path);
  
              try {
  
                  fis = new FileInputStream(f);
  
              } catch (FileNotFoundException e) {
  
              }
  
              return newFixedLengthResponse(Response.Status.OK, "m3u8", fis, f.length());
  
          }
  
  
  
          if(session.getUri().endsWith("ts")){
  
              String path = Environment.getExternalStorageDirectory().toString() + "/s3" + session.getUri();
  
  
  
              FileInputStream fis = null;
  
              File f = new File(path);
  
              try {
  
                  fis = new FileInputStream(f);
  
              } catch (FileNotFoundException e) {
  
  
  
              }
  
              return newFixedLengthResponse(Response.Status.OK, "ts", fis, f.length());
  
          }
  
  
  
          String path = Environment.getExternalStorageDirectory().toString() + "/s3/master.m3u8";
  
  
  
          FileInputStream fis = null;
  
          File f = new File(path);
  
          try {
  
              fis = new FileInputStream(f);
  
          } catch (FileNotFoundException e) {
  
          }
  
          return newFixedLengthResponse(Response.Status.OK, "m3u8", fis, f.length());
  
      }
  
  }

  I have transcoded the video using ffmpeg. I need to know that which data or key need to be returned when the dataKey url is called. I have the encrypted the video using these key :

  key=617D8A125A284DF48E3C6B1866348A3F
  
  IV=5ff82ce11c7e73dcdf7e73cacd0ef98

  I can not understand which of them are need to be returned from the datakey url. Both of them are not working. Exoplayer is sending the error message :java.security.InvalidKeyException: Unsupported key size

  can Any one help me about this ?