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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

• libFLAC : new function returns client_data from decoder

  4 décembre 2017, par Christophe DUMONT

  libFLAC : new function returns client_data from decoder
  Signed-off-by : Erik de Castro Lopo <erikd@mega-nerd.com>
  

  • [DH] src/libFLAC/include/protected/stream_decoder.h
  • [DH] src/libFLAC/stream_decoder.c

• How to make cropping when doing motion-tracking look super smooth ? (using cv2 and yolo v8)

  4 décembre 2024, par Thomas Lancer

  I'm using yolo to track a face in a video on a frame by frame basis, and then I'm using cv2 to crop the video (with some padding) around the speakers face so it creates a motion tracking type effect. (short example here : https://www.instagram.com/reel/DCIFkFEObkE/?hl=en)

  


  The problem I'm running into is my final crop looks "shaky". Like it's flickering a bit. I think this is because every frame yolo is updating the coordinates, and so there's a slight change in x, y and because of that it creates this shakiness/flickering effect. Here's what mine looks like compared to the example : https://drive.google.com/file/d/1MKHWK-5EH5abSq6i32r71GWld76tN1GP/view?usp=sharing

  


  You can see there's this "shakiness" type look to it. it's especially apparent when the speaker is relatively still.

  


  I've tried doing an exponential moving average and a few other averaging techniques but none have fixed it.

  


  Is my fundamental approach of doing a frame by frame crop wrong ? or is there just some smoothing algorithm or some dumb mistake that you think I may be making ? Any advice is mega appreciated !