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• Is it possible to adjust position of gdigrab recording region during recording ?

  30 novembre 2020, par adelima

  I'm using ffmpeg for recording video from defined desktop region by starting ffmpeg.exe as process with arguments like so :

  


      public static void StartRecording(Video v) {
        string outPath = Path.Combine(Application.StartupPath, "rec", $"{v.FileName}.mkv");
        v.FFMPEG = new Process {
            StartInfo = new ProcessStartInfo() {
                Arguments = $"-hide_banner -y -thread_queue_size 512 -f gdigrab -offset_x {v.Bounds.X} -offset_y {v.Bounds.Y} -video_size {v.Bounds.Width}x{v.Bounds.Height} -show_region 0 -i desktop -vf \"scale=trunc(iw/2)*2:trunc(ih/2)*2\" -c:v libx264 -preset ultrafast -crf 18 -pix_fmt yuv420p \"{outPath}\"",
                WindowStyle = ProcessWindowStyle.Hidden,
                CreateNoWindow = true,
                UseShellExecute = false,
                FileName = Path.Combine(Application.StartupPath, "bin", "ffmpeg.exe"),
                RedirectStandardOutput = true,
                RedirectStandardInput = true,
                RedirectStandardError = true,
            }
        };
        v.FFMPEG.Start();

        new Thread(() => {
            using(StreamReader sr = v.FFMPEG.StandardError) {
                while(!sr.EndOfStream) {
                    Debug.WriteLine(sr.ReadLine());
                }
            }
        }).Start();
    }

    public static void StopRecording(Video v) {
        using(StreamWriter sw = v.FFMPEG.StandardInput) {
            sw.WriteLine("q\n");
        }
        v.FFMPEG.WaitForExit();
        v.FFMPEG.Dispose();
    }


  


  Is it possible to make changes to the -offset_x and -offset_y arguments during recording ? I'm drawing the recording region bounds with directx and want to add a titlebar to it which can be dragged to move the recording region, but I'm not sure how I would let ffmpeg know that I want these offsets changed or whether it's even possible.

  


• How to use PHP FFMPEG to alter audio binary header bytes offset

  27 mai 2019, par SomniusX

  I use the following method to create a WNB file that is flashable to my Electric Unicycle Ninebot Z10

  First audacity to make the file raw pcm 16khz 16bit mono littleendian
  Then wnb-slicer golang app to convert that raw file into wnb.

  Today i did the same with ffmpeg

  ffmpeg -i $1 -acodec pcm_s16le -f s16le -ac 1 -ar 16000 -acodec pcm_s16le $1.raw
  
  ../wnb-slicer-master/wnb-slicer -file-name $1.raw

  where $1 is the original file

  About an hour ago i did the ffmpeg part with php-ffmpeg but i can’t have golang run on a webserver.

  So i thought if ffmpeg does bytes manipulation like the golang app does here

  Thank you in advance !

  p.s. this project will help all electric unicycle owners of the Z series wheels to change audio voices/sounds on their wheels !!

• video streaming using recent frames only

  30 juillet 2019, par Max Paython

  I am trying to create a live video chat application, I am dealing with latency problems but these problems are not produced by encoding or overhead, rather from the definition of streaming itself.

  For example if I start the client program 15 seconds after the server program (start listening the port 15 seconds late), the client tries the play the 15 second old stream. (and fails because of the lack of I-frames introduced by x264 zero-latency, but this is not important)

  But I am trying to make it live. Old frames should be discarded and and the most recent frame should be showing (to a 1 second buffer maybe). I failed at doing this so I wanted to wait streaming until the peer is connected, but my goal is actually the first one.

  I am using ffmpeg for streaming. Can ffmpeg wait streaming until a single client starts listening (or connects) the port.

  How does applications like Skype or Hangouts handle this ? In these applications, if a user suddenly stops listening to the port (internet error for example) for 5 seconds, the chat will continue regularly after the connections is restored, and that user will not see the 5 second old frame but the new one. However I was not able to achieve this.