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• record Linux Wayland/DRM screen using ffmpeg's kmsgrab device with superimposed webcam

  7 février 2020, par nrdxp

  Setup is Linux, ffmpeg using kabylake iGPU.

  I am capturing a running sway instance using the kmsgrab device, which requires the use of a hardware backend to coherently process the image on my hardware. Only VA API fits this bill. I want to overlay the webcam in the bottom right corner during encoding. However, attempts at manipulating the filter graph to accomplish this have been unsuccessful. This is ultimately for Twitch/Tube stream.

  Right now, I am actually capturing the webcam to an sdl window, and simply recording the screen using separate instances of ffmpeg. This doesn’t actually solve my problem since the window is easily disguised by workspace switching or other windows.

  This is the workaround :

  #!/usr/bin/env zsh
  
  
  
  # record webcam and open it in sdl window
  
  ffmpeg -v quiet -hide_banner \
  
    -re -video_size 640X480 -hwaccel vaapi -vaapi_device /dev/dri/renderD128 -i /dev/video0 \
  
    -vf 'format=nv12,hwupload' -c:v hevc_vaapi -f hevc - \
  
    | ffmpeg -v quiet -i - -f sdl2 - &
  
  
  
  # wait for webcam window to open
  
  until swaymsg -t get_tree | grep 'pipe:' &>/dev/null; do
  
    sleep 0.5
  
  done
  
  
  
  # position webcam in the bottom right corner of screen using sway
  
  swaymsg floating enable
  
  swaymsg resize set width 320 height 240
  
  swaymsg move position 1580 795
  
  swaymsg focus tiling
  
  
  
  #screencast
  
  ffmpeg -format bgra -framerate 60 -f kmsgrab -thread_queue_size 1024 -i - \
  
    -f alsa -ac 2 -thread_queue_size 1024 -i hw:0 \
  
    -vf 'hwmap=derive_device=vaapi,scale_vaapi=w=1920:h=1080:format=nv12' \
  
    -c:v h264_vaapi -g 120 -b:v 3M -maxrate 3M -pix_fmt vaapi_vld -c:a aac -ab 96k -threads $(nproc) \
  
    output.mkv
  
  
  
  kill %1

• Record stream using SDP file & ffmpeg

  27 avril 2023, par john

  I have a stream created using ffmpeg using the following command :

  



  ffmpeg -re -thread_queue_size 4 -i video.mp4 -strict -2 -vcodec copy -an -f rtp rtp://127.0.0.1:51372 -sdp_file test.sdp


  



  This creates a .sdp file while streaming the local video file over RTP.

  



  The SDP file :

  



  v=0
o=- 0 0 IN IP4 127.0.0.1
s=Serenity - HD DVD Trailer
c=IN IP4 127.0.0.1
t=0 0
a=tool:libavformat 58.29.100
m=video 51372 RTP/AVP 96
b=AS:4674
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1; sprop-parameter-sets=Z2QAKaw05QFAFuhAAZdOwExLQCPGDEWA,aO68sA==; profile-level-id=640029


  



  Now I want to use another ffmpeg instance to record this stream and save to a file (assuming its another machine in the network).

  



  I tried the following command but it is giving an error.

  



  ffmpeg -i test.sdp -c copy -flags +global_header -f segment -segment_time 60 -protocol_whitelist file,udp,rtp -segment_format_options movflags=+faststart -reset_timestamps 1 test.mp4


  



  The error :

  



  Protocol 'rtp' not on whitelist 'file,crypto'!
custom.sdp: Invalid data found when processing input


  


• ffmpeg blackdetect, start_black value to mkv chapter ?

  2 décembre 2019, par stackoverflowknitter

  I’m trying to do automatic detect chapter with blackdetect with ffmpeg.

  When I use blackdetect I get result but what is the result ? Its not frames ? Also. Is it possible to do a script/bat-file (for windows 10, powershell or cmd) to convert the result to a "mkv xml-file" so It can be imported with mkvtoolnix ?

  ffmpeg -i "movie.mp4" -vf blackdetect=d=0.232:pix_th=0.1 -an -f null - 2>&1 | findstr black_duration > output.txt

  result :

   black_start:2457.04 black_end:2460.04 black_duration:3
  
   black_start:3149.46 black_end:3152.88 black_duration:3.41667
  
   black_start:3265.62 black_end:3268.83 black_duration:3.20833
  
   black_start:3381.42 black_end:3381.92 black_duration:0.5
  
   black_start:3386.88 black_end:3387.38 black_duration:0.5
  
   black_start:3390.83 black_end:3391.33 black_duration:0.5
  
   black_start:3824.29 black_end:3824.58 black_duration:0.291667
  
   black_start:3832.71 black_end:3833.08 black_duration:0.375
  
   black_start:3916.29 black_end:3920.29 black_duration:4