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• FFmpeg h264_v4l2m2m encoder changing aspect ratio from 16:9 to 1:1 with black bars

  8 janvier, par LycoReco2007

  When switching from libx264 to h264_v4l2m2m encoder in FFmpeg for YouTube streaming, the output video's aspect ratio changes from 16:9 to 1:1 with black bars on the sides, despite keeping the same resolution settings.

  


  Original working command (with libx264) :

  


  ffmpeg -f v4l2 \
    -input_format yuyv422 \
    -video_size 1280x720 \
    -framerate 30 \
    -i /dev/video0 \
    -f lavfi \
    -i anullsrc=r=44100:cl=stereo \
    -c:v libx264 \
    -preset ultrafast \
    -tune zerolatency \
    -b:v 2500k \
    -c:a aac \
    -b:a 128k \
    -ar 44100 \
    -f flv rtmp://a.rtmp.youtube.com/live2/[STREAM-KEY]


  


  When I replaced libx264 with h264_v4lm2m, it always produce a square resolution, and it automatically adds black bars to the top and the bottom of the sides of the camera. I currently using a Rasberry Pi 4 model B, with a webcam that I believe supports the 16:9 ratio (I've verified using v4l2-ctl --list-formats-ext -d /dev/video0 command)

  


  I've tried the follows :

  


  

  • Adding -aspect 16:9 parameter in the ffmpeg command

  


  • Adding video filters such as -vf "scale=1280:720:force_original_aspect_ratio=decrease,pad=1280:720:(ow-iw)/2:(oh-ih)/2,setsar=1"
None of these give me the correct aspect ratio.

  


  


  How can I make the h264_v4l2m2m encoder maintain the original 16:9 aspect ratio without adding black bars ? Is this a known limitation of the encoder, or am I missing some required parameters ?

  


• Is ffmpeg's chromakey filter broken when matching black/white ?

  7 janvier 2023, par Taylor Brown

  I have a file, colors.png. It looks like this :

  



  Let's say I want to make the red square transparent. When I run ffmpeg -i colors.png -filter_complex "[0]chromakey=0xff0000:similarity=0.1:blend=0.0[out]" -map "[out]" colors-rm-red.png (notice I use similarity=0.1 to make this work), I get exactly that :

  



  How about making the blue square transparent ? ffmpeg -i colors.png -filter_complex "[0]chromakey=0x0000ff:similarity=0.1:blend=0.0[out]" -map "[out]" colors-rm-blue.png works too !

  



  But what about replacing black ? ffmpeg -i colors.png -filter_complex "[0]chromakey=0x000000:similarity=0.1:blend=0.0[out]" -map "[out]" colors-rm-black.png gives me this :

  



  And likewise, replacing white with ffmpeg -i colors.png -filter_complex "[0]chromakey=0xffffff:similarity=0.1:blend=0.0[out]" -map "[out]" colors-rm-white.png gives me the same result :

  



  Why is this ? Even if I use similarity=0.01, which according to the docs "matches only the exact key color", this still doesn't work when I'm trying to make black/white transparent. Is ffmpeg broken, or am I misunderstanding the chromakey filter ?

  


• FFMPEG - Add black frames about 10 seconds at the end of .MP4 video with text

  26 août 2015, par Muhammad Jabbar

  I want to add black frames with text at the end of the someVideo.MP4 video using FFMPEG. The input and output video format will be someVideo.MP4

  Last 10 seconds of the video should be like below screen :
  

  Please guide, is it possible to do ? If yes, please guide me with an example code ?

  Many thanks !