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• Desktop recording with ffmpeg won't play in anything but VLC

  12 mai 2022, par Alex

  I'm creating a desktop application for fun/education. Its primary function is to record my PCs screen and have a pretty UI to play this back. I am recording with ffmpeg like so :

  


  ffmpeg -thread_queue_size 1024 -f gdigrab -framerate 50 -video_size 1920x1080 -i desktop -f dshow -i audio="virtual-audio-capturer" -r 50 -preset fast -c:v h264_nvenc -qp 23 "D:/vid.mp4"


  


  At first glance this seems fine, a file is created and playing it back in VLC media player also works fine.

  


  The problem is that I can't play this back in anything else. Windows apps (videos + media player) just freeze up/provide no clue as to the problem. My end goal is to embed this into a HTML5 player to fit with the electron/react framework I'm writing my application in. This also doesn't play in a similar fashion.

  


  I ran mediainfo on the file in WSL and got the following :

  


  General
Complete name                            : vid.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/avc1/mp41)
File size                                : 544 MiB
Duration                                 : 1 min 15 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 60.4 Mb/s
Writing application                      : Lavf59.10.100

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High 4:4:4 Predictive@L4.2
Format settings                          : 1 Ref Frames
Format settings, CABAC                   : No
Format settings, Reference frames        : 1 frame
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 1 min 15 s
Bit rate mode                            : Variable
Bit rate                                 : 60.3 Mb/s
Maximum bit rate                         : 2 000 kb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 50.000 FPS
Color space                              : RGB
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.581
Stream size                              : 543 MiB (100%)
Color range                              : Full
Matrix coefficients                      : Identity
Codec configuration box                  : avcC

Audio
ID                                       : 2
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : mp4a-40-2
Duration                                 : 1 min 15 s
Source duration                          : 1 min 15 s
Bit rate mode                            : Constant
Bit rate                                 : 132 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz


  


  I also saw this thread (ffmpeg created timelapse won’t play on other players than VLC) suggesting the bit rate may be the problem but having tried the suggestions there had no luck.

  


  At a glance I suspected the "Codec ID" field as with comparison to other MP4 files that windows does play it is slightly different, i.e. :

  


  isom (isom/iso2/avc1/mp41) vs mp42 (mp42/mp41/isom/avc1)

  


  However fiddling with the ffmpeg encoder settings I managed to vary this and still could not play the video back.

  


  Also including the ffprobe output :

  


  ffprobe version 4.2.4-1ubuntu0.1 Copyright (c) 2007-2020 the FFmpeg developers
  built with gcc 9 (Ubuntu 9.3.0-10ubuntu2)
  configuration: --prefix=/usr --extra-version=1ubuntu0.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-nvenc --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'vid.mp4:
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf59.10.100
  Duration: 00:01:15.50, start: 0.000000, bitrate: 60414 kb/s
    Stream #0:0(und): Video: h264 (High 4:4:4 Predictive) (avc1 / 0x31637661), gbrp(pc, gbr/unknown/unknown), 1920x1080 [SAR 1:1 DAR 16:9], 60277 kb/s, 50 fps, 50 tbr, 12800 tbn, 100 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 132 kb/s (default)
    Metadata:
      handler_name    : SoundHandler


  


• ffmpeg run from c# Process not closing when using '-i anullsrc'

  1er octobre 2022, par Brown Bear

  I am generating a large collection MP4 videos from an OpenGL source. This has worked perfectly so far but I recently noticed that some TV media player don't like video without audio, see here for more info.

  


  So far i hve been using the following code :

  


      private bool StartRecording()
    {
        _ffmpeg = new Process();
        _ffmpeg.StartInfo.FileName = "ffmpeg.exe";
        _ffmpeg.StartInfo.Arguments = $"-f rawvideo -pix_fmt rgba -s {RecordSize.Width}x{RecordSize.Height} -r 30 -i - -c libx264 -crf 17 -pix_fmt yuv420p -b:v 1024k -bufsize:v 1835008 {RecordFile} -tune animation";
        _ffmpeg.StartInfo.RedirectStandardInput = true;
        _ffmpeg.Start();

        if(_ffmpeg.HasExited)
        {
            IsRecording = false;
            return false;
        }
        return true;
    }

    private void RecordFrame(RenderUpdate update)
    {
        if (_ffmpeg == null)
            return;

        var frame = Project.RecordFrame(update);
        var data = new byte[frame.Length];
        var height = RecordSize.Height;
        var width = RecordSize.Width;

        for (var k = 0; k < height; k++)
        {
            var j = height - k - 1;
            Buffer.BlockCopy(
                frame, k * width * 4,
                data, j * width * 4,
                width * 4);
        }

        _ffmpeg.StandardInput.BaseStream.Write(data, 0, data.Length);
    }

    private void StopRecording()
    {
        Project.StopRecording();
        if (_ffmpeg == null)
            return;

        _ffmpeg.StandardInput.Flush();
        _ffmpeg.StandardInput.Close();
        _ffmpeg.Close();
        _ffmpeg.Dispose();
    }


  


  And it has worked perfectly until I modified the 'ffmpeg' cmd line arguments to include '-i anullsrc' for the audio.

  


    _ffmpeg.StartInfo.Arguments = $"-f rawvideo -pix_fmt rgba -s {RecordSize.Width}x{RecordSize.Height} -r 30 -i - -f lavfi -i anullsrc=channel_layout=mono:sample_rate=8k -c:v libx264 -crf 17 -pix_fmt yuv420p -b:v 1024k -bufsize:v 1835008 {RecordFile} -tune animation";


  


  The moment I add '-f lavfi -i anullsrc' to the cmd line the call to 'StopRecording()' has no effect and ffmpeg continues to run.

  


  I can manually stop it by closing the console window or even using ctrl-c, but the job needs to be automated so this is just not an option.

  


  Ultimately my question is Why is ffmpeg behaving this way ?

  


  I've come up with a couple of work arounds, but I don't like either :

  


  

  1. Post process the videos as per the link I mentioned earlier. Not practical. I need to generate 1000s of videos and a single batch of 350 takes around 6 hours. 50% of that time is consumed by ffmpeg encoding, so to re-encode them all just to add a null audio track would nearly double the time.

  


  2. Try to push a 'ctrl-c' through to the ffmpeg process as per this post. I did some quick tests with 'GenerateConsoleCtrlEvent' without sucess, and the idea of having to manually start and stop the Process via 'kernel32.dll' seems excessive not to mention old school.

  


  


  Any insight would be greatly appreciated.

  


• Lib x : display problem related to window pixel color changes with the mlx_put_pixel() function [closed]

  15 janvier 2023, par Jordan Riga

  I'm stuck on a project that I have to return for school.
I have to make a 3D game with the minilibx in C, the problem being that I try to make the graphic part work but it doesn't work (display pixels on the screen).
And all this same with the examples that I found of school 42 on the internet in that link https://harm-smits.github.io/42docs/libs/minilibx.
All configuration has been done.

  


  Could there be a possible configuration problem ? I'm working on Kali Linux (Even using a VM on Ubuntu it didn't work).

  


  In short my question is what can be the different reasons why the graphical part of minilibx independently of events, loops and etc does not work without errors ?