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• FFmpeg How disable video output ?

  29 août 2022, par NoonanRosenblum

  With ffmpeg 4.3.1, I want to use the "blackframe" filter.

  


  This filter outputs text results in the console each time a black frame is detected in the input video.

  


  ffmpeg -i Input.avi -filter_complex "blackframe" Output.mkv
> [Parsed_blackframe_1 @ 0x7ff48c607a80] frame:206 pblack:100 ...


  


  I do not need to create the Output.mkv video, as console result is enough.

  


  Unfortunately I am not able to find in the documentation how disable output video and still run the filter. From the main options section https://www.ffmpeg.org/ffmpeg.html#Main-options and examples elsewhere I tried :

  


  

  • -f null

  


  • or -y NULoption in the -pass option example of the doc

  


  


  But none of these commands works :

  


  ffmpeg -i Video.avi -filter_complex "black frame" -f null
> Filter blackframe has an unconnected output

ffmpeg -i Video.avi -filter_complex "black frame" -y NUL
> [NULL @ 0x7ffbe7026200] Unable to find a suitable output format for 'NUL'
> NUL: Invalid argument


  


  How can I disable video output ?

  


  Where is it explain in the documentation ?

  


• ffmpeg convert white color to alpha

  11 janvier 2021, par tony

  Hello i took a picture with my camera :a drawing of a square frame on a white paper ; i'm trying to convert the white to transparent and keep the black color frame.

  


  So i started making 1 palette with only 2 colors to make the colors uniform and 1 palette to add the transparency

  


  ffmpeg -f lavfi -i "color=color=white:100x100" -f lavfi -i "color=color=black:100x100" -filter_complex "[0][1]hstack" -frames:v 1 blackwhite.png`
ffmpeg -i blackwhite.png -filter_complex "[0]split[a][b];[a]palettegen[pal1];[b]palettegen=reserve_transparent=on:transparency_color=white[pal2]" -map [pal1] palette1.png -map [pal2] palette2.png


  


  then i mapped the image png of the frame to convert the white to transparent and overlayed the result to a red background

  


  ffmpeg -i image.png -i palette1.png -i palette2.png -i background.png -filter_complex "[0:v][1:v]paletteuse=dither=bayer[a],[a]split[a1][a2];[a1][2:v]paletteuse=alpha_threshold=128[c];[3:v][c]overlay[d]" -map [a2] -c:v png out.png -map [d] -c:v png out1.png


  


  the png mapped to the first palette (as a test) comes as it should be, pure black and white,the second comes with no transparency at all and covers the background
what am i doing wrong ?

  


• DeckLink 4K Extreme capture videos

  15 avril 2015, par tomas kedden

  I have DeckLink 4K extreme Capture card from Black Magic and i want to capture videos from HDMI input from my SET-Top-Box that it output format yuv4:2:2 on HDMI.

  I set’up the bmdtool to capture frame and ffmpeg 2.6 to convert captured frames from yuv422 to mpg file (obtain video files - i want mpg or mp4)

  I use this command for :

  ./bmdcapture -m 8 -V 3 -C 1 -F nut -f pipe:1 | ffmpeg -re -s 1920x1080 -pix_fmt yuv422p -i - -r 30 -f mpeg2videio -b:v 5M -y videoCaptured.mpg

  Videos format : 1920x1080-30

  But i always obtain a corrupted bmp file but when i use MediaExpress Black Magic SOtware it can display the result correctly whith capture file format as - AVI 10bit YUV.

  So can you help me on that.