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• 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 ?

  


• 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 in Android not rendering Arabic characters

  14 octobre 2024, par Henry Smith

  I have an Android app that uses FFMPEG to add text overlays onto a mp4 video files.

  


  It works fine with a Latin alphabet, but when I try and add Arabic characters as an overlay on the .mp4 file, the output video displays rectangles (assuming unrecognised characters).

  


  FFMPEG command example is :
-y -i video-in.mp4 -preset ultrafast -vf "[in]drawtext=text='نقطة البداية قلا':enable='between(t, 0,5)':fontcolor=White:fontsize=20:box=1:boxcolor=black@0.5:boxborderw=5:x=(w-text_w)/2:y=(h-text_h)/2,drawtext=text='وصلات مزاحجة كبيرة الإزاحة (من ١٢ إلى ٤)':enable='between(t, 15,20)':fontcolor=White:fontsize=20:box=1:boxcolor=black@0.5:boxborderw=5:x=(w-text_w)/2:y=(h-text_h)/2[out]" -r 24 "video-out.mp4"

  


  Output mp4 video comes out a below :
enter image description here

  


  Using Android SDK Version 13, FFMPEG plugin : com.arthenica:mobile-ffmpeg-full-gpl:4.4

  


  Class example code :

  


  import com.arthenica.mobileffmpeg.ExecuteCallback
import com.arthenica.mobileffmpeg.FFmpeg

class VideoUtils() {

    fun addTextOverlay(inputFile: String, outputFile: String, text: String) {
        // create video filter for overlay text between 0 - 5 seconds, centre aligned, white font and black box
        val tempTextString =
            "drawtext=text='$text:enable='between(t, 0,5)':fontcolor=White:fontsize=20:box=1:boxcolor=black@0.5:boxborderw=5:x=(w-text_w)/2:y=(h-text_h)/2"

        // create FFMPEG command
        val cmd =
            "-y -i $inputFile -preset ultrafast -vf \"[in]$tempTextString[out]\" -r 24 \"$outputFile\""

        FFmpeg.execute(cmd)
    }
}