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• How can I transform a sequence of images into a playable video using LibVLCSharp ?

  9 février 2021, par adamasan

  I have a sequence of images that I was able to extract from a video using LibVLCSharp. This sample to be more specific. I'm creating a small video library manager for learning purposes, and I would like to extract frames and create thumbnails to play when the user hovers the mouse over the previewer.

  


  Using the aforementioned sample I was able to create a WPF UI around the same loging and extract the frames from a video file. However what I want now is to convert these extracted frames into a video file, using them as preview for the video, just like happens on YouTube.

  


  I wasn't able, however, to find out how to achieve this using LibVLCSharp or just LibVLC. Using this answer on Super User I was able to achieve my goal and put those frames together into a video using ffmpeg.

  


  I haven't taken the time yet to study FFmpeg.Autogen, so I don't know if I would be able to extract the frames from the video files in the same way I can do with LibVLCSharp, but I don't see with good eyes using both libraries on my application, one to export the frames and one to generate these frames into a video.

  


  So, is there a way to get the output frames and convert them into a playable video using LibVLCSharp (or libvlc) itself ?

  


• FFMPEG is really slow at extracting subtitles

  3 mars 2021, par Gustav P Svensson

  I'm trying to extract the subtitles from a 1080P video, around 40min long. I'm currently using this command (using fluent-ffmpeg in node, but the translated command is this) :

  


  ffmpeg -threads 3  -map 0: -c copy 


  


  This command takes about 20-30 min to complete. I've searched quite a lot on how to speed up this process, if I look at my task manager I can see that ffmpeg is using 0.1% of the CPU which makes me think that it's possible to speed up this process.

  


  I'm not sure if the -threads option is actually doing anything when extracting subtitles but I don't think it should make it slower atleast ?

  


  So my question is, is it possible to speed up this process ? I appriciate any help.

  


  Full FFMPEG log:
fmpeg version 3.4.8-0ubuntu0.2 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.5.0-3ubuntu1~18.04)
  configuration: --prefix=/usr --extra-version=0ubuntu0.2 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
Input #0, matroska,webm, from '/home/test.mkv:
  Metadata:
    encoder         : libebml v1.3.6 + libmatroska v1.4.9
    creation_time   : 2019-03-14T16:46:55.000000Z
  Duration: 00:41:20.29, start: 0.000000, bitrate: 6430 kb/s
    Stream #0:0: Video: h264 (Main), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
    Metadata:
      BPS-eng         : 5788926
      DURATION-eng    : 00:41:20.020000000
      NUMBER_OF_FRAMES-eng: 59461
      NUMBER_OF_BYTES-eng: 1794581562
      _STATISTICS_WRITING_APP-eng: mkvmerge v31.0.0 ('Dolores In A Shoestand') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2019-03-14 16:46:55
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:1(eng): Audio: eac3, 48000 Hz, 5.1(side), fltp, 640 kb/s (default)
    Metadata:
      title           : English
      BPS-eng         : 640000
      DURATION-eng    : 00:41:20.288000000
      NUMBER_OF_FRAMES-eng: 77509
      NUMBER_OF_BYTES-eng: 198423040
      _STATISTICS_WRITING_APP-eng: mkvmerge v31.0.0 ('Dolores In A Shoestand') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2019-03-14 16:46:55
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:2(eng): Subtitle: subrip
    Metadata:
      BPS-eng         : 80
      DURATION-eng    : 00:40:22.295000000
      NUMBER_OF_FRAMES-eng: 645
      NUMBER_OF_BYTES-eng: 24473
      _STATISTICS_WRITING_APP-eng: mkvmerge v31.0.0 ('Dolores In A Shoestand') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2019-03-14 16:46:55
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:3(eng): Subtitle: subrip
    Metadata:
      title           : SDH
      BPS-eng         : 86
      DURATION-eng    : 00:40:31.012000000
      NUMBER_OF_FRAMES-eng: 709
      NUMBER_OF_BYTES-eng: 26142
      _STATISTICS_WRITING_APP-eng: mkvmerge v31.0.0 ('Dolores In A Shoestand') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2019-03-14 16:46:55
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
Output #0, srt, to 'test6.srt':
  Metadata:
    encoder         : Lavf57.83.100
    Stream #0:0(eng): Subtitle: subrip
    Metadata:
      BPS-eng         : 80
      DURATION-eng    : 00:40:22.295000000
      NUMBER_OF_FRAMES-eng: 645
      NUMBER_OF_BYTES-eng: 24473
      _STATISTICS_WRITING_APP-eng: mkvmerge v31.0.0 ('Dolores In A Shoestand') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2019-03-14 16:46:55
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
Stream mapping:
  Stream #0:2 -> #0:0 (copy)
Press [q] to stop, [?] for help
size=      46kB time=00:40:36.68 bitrate=   0.2kbits/s speed=11.6x    
video:0kB audio:0kB subtitle:24kB other streams:0kB global headers:0kB muxing overhead: 94.438766%


  


• FFmpeg Process Priority at screenrecording

  24 avril 2021, par Andrew

  I made formula for screenrecording via FFmpeg, and it works with Counter-Strike and Dota 2.
But it doesn't work with World of Tanks. So I faced with troubles. World of Tanks crashs after few minutes. And speed of recording is less then 1x (about 0.87x and it become slower and slower). So I think that I need to raise up the priority process of FFmpeg.
Look for test of it on my Youtube Channel : my test of ffmpeg screen recording

  


  So I would like to set 'High' or 'Realtime' priority for this process automatically !

  


  But right now I can do it via 2 ways :

  


  

  1. via Task Manager ;

  


  2. via second PowerShell Window and second "copy-paste".

  


  


  But both methods require a time (5-20 seconds). It is no good.
I cannot to set Start-Process ffmpeg -NoNewWindow -Wait -ArgumentList for setting PriorityClass as here stackoverflow because my ArgumentList of FFmpeg is too huge.
And I cannot start-process pwsh -ArgumentList for new powershell window for setting PriorityClass. It write me about an error.
My tested formula for Youtube :

  


  ffmpeg -hide_banner -loglevel +repeat+level+info `
-f dshow -thread_queue_size 8192 -audio_buffer_size 100 -rtbufsize 2147M `
-i 'audio=@device_sw_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\{8E146464-DB61-4309-AFA1-3578E927E935}' `
-f dshow -thread_queue_size 8192 -audio_buffer_size 100 -rtbufsize 2147M `
-i 'audio=@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\wave_{472DBE92-04B3-48AB-A937-ED4CD6A85625}' `
-f gdigrab -hwaccel_device cuda -hwaccel cuda -hwaccel_output_format cuda -video_size 1920:1080 -thread_queue_size 8192 -draw_mouse 1 -show_region 0 -offset_x 0 -offset_y 0 -rtbufsize 2147M -probesize 500M -analyzeduration 500M -framerate 60 -i desktop `
-noautoscale -shortest `
-map '0:a:0' -c:a copy -f wav "FFmpeg_Screen_Recording_$(get-date -f yyyy-MM-dd_HH-mm-ss).wav" `
-map '1:a:0' -c:a copy -f wav "FFmpeg_WebCAM_Recording_$(get-date -f yyyy-MM-dd_HH-mm-ss).wav" `
-map '2:v:0' -c:v h264_nvenc -gpu 0 -vsync 1 -r 60 -video_size 1920x1080 -video_track_timescale 60 -copytb 0 -delay 0 -rc constqp -qp 0 -rc-lookahead 0 -zerolatency 1 -maxrate:v 512M -bufsize:v 512M -pix_fmt yuv444p -profile:v high444p -preset p1 -tune ull -level 6.2 -coder vlc -weighted_pred 0 `
-f mov "FFmpeg_Screen_Recording_$(get-date -f yyyy-MM-dd_HH-mm-ss).mov"


  


  My current formula for High priority - first tab :

  


  start-process pwsh -ArgumentList '-noexit' 
Get-Process -name 'pwsh' | foreach { $_.PriorityClass = "High" }
$startExe = ffmpeg -hide_banner -loglevel +repeat+level+info `
-f dshow -thread_queue_size 8192 -audio_buffer_size 100 -rtbufsize 2147M `
-i 'audio=@device_sw_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\{8E146464-DB61-4309-AFA1-3578E927E935}' `
-f dshow -thread_queue_size 8192 -audio_buffer_size 100 -rtbufsize 2147M `
-i 'audio=@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\wave_{472DBE92-04B3-48AB-A937-ED4CD6A85625}' `
-f gdigrab -hwaccel_device cuda -hwaccel cuda -hwaccel_output_format cuda -video_size 1920:1080 -thread_queue_size 8192 -draw_mouse 1 -show_region 0 -offset_x 0 -offset_y 0 -rtbufsize 2147M -probesize 500M -analyzeduration 500M -framerate 60 -i desktop `
-noautoscale -shortest `
-map '0:a:0' -c:a copy -f wav "FFmpeg_Screen_Recording_$(get-date -f yyyy-MM-dd_HH-mm-ss).wav" `
-map '1:a:0' -c:a copy -f wav "FFmpeg_WebCAM_Recording_$(get-date -f yyyy-MM-dd_HH-mm-ss).wav" `
-map '2:v:0' -c:v h264_nvenc -gpu 0 -vsync 1 -r 60 -video_size 1920x1080 -video_track_timescale 60 -copytb 0 -delay 0 -rc constqp -qp 0 -rc-lookahead 0 -zerolatency 1 -maxrate:v 512M -bufsize:v 512M -pix_fmt yuv444p -profile:v high444p -preset p1 -tune ull -level 6.2 -coder vlc -weighted_pred 0 `
-f mov "FFmpeg_Screen_Recording_$(get-date -f yyyy-MM-dd_HH-mm-ss).mov"


  


  Second tab (second copy-paste action) :

  


  Get-Process -name 'ffmpeg' | foreach { $_.PriorityClass = "High" }


  


  How can I do it in the only one action ?