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• ffmpeg watermark transparent background

  6 mai 2013, par ionutvmi

  I'm trying to add a watermark to a video file but i'm having problems with the background of the watermark because i want it to be transparent.

  My approach is like this : i make a png file the size of the video with transparent background like this

  $im = imagecreatetruecolor($width, $height); 
  
  $almostblack = imagecolorallocate($im,254,254,254); 
  
  imagefill($im,0,0,$almostblack); 
  
  $black = imagecolorallocate($im,0,0,0); 
  
  imagecolortransparent($im,$almostblack); 
  
  
  
  $textcolor = imagecolorallocate($im, 255, 0, 0);
  
  
  
  // Write the string at the top left
  
  imagestring($im, 5, 0, 0, 'Hello world!', $textcolor);
  
  
  
  imagepng($im, $img);
  
  imagedestroy($im);

  and then i add it to the video like this

  exec("/usr/bin/ffmpeg -y -i '$file->path' -sameq -vf 'movie=$img [logo]; [in][logo] overlay=main_w-overlay_w:main_h-overlay_h [out]' '$new_path'");

  the watermark is added but it's background is not transparent.

  Any idea what i'm doing wrong ?

  UPDATE : it turns out it works just fine for other png images so the problem must be in the way i build the png file any ideas why it doesn't work that way ?

• Ideal bitrates for different video resolutions

  15 octobre 2018, par Ramesh Navi

  I am building a Video-on-demand service for a closed community. I using FFMPEG for video processing and dash.js for adaptive bitrate player with custom resolution selector. Can somebody please suggest what ideal bitrates should I use while video/audio transcoding ?

  I am talking about -b:v and -ab option

  ffmpeg -i vid.mp4 -c:v libvpx-vp9 -keyint_min 150 \
  
  -g 150 -tile-columns 4 -frame-parallel 1  -f webm -dash 1 \
  
  -an -vf scale=144:-1 -b:v 120k -dash 1 video_1.webm \
  
  -an -vf scale=240:-1 -b:v 250k -dash 1 video_2.webm \
  
  -an -vf scale=360:-1 -b:v 500k -dash 1 video_3.webm \
  
  -an -vf scale=480:-1 -b:v 750k -dash 1 video_4.webm \
  
  -an -vf scale=720:-1 -b:v 1500k -dash 1 video_5.webm

  And

  ffmpeg -i vid.mp4 -vn -acodec libvorbis -ab 96k -dash 1 audio_96k.webm

  Any suggestions/hacks or examples to tackle real-world network situations are appreciated.

• How play AVI with sound by OpenCV on Win32

  4 janvier 2015, par Andrei Shumilov

  I need play AVI by OpenCV and any sound player (vfw/ffmpeg...) on Win32. It seems to me this is very secret or useless thing ’cos I found only one sample in the world : Audio output with video processing with opencv

  Mr. Karl Phillip wrote there :
  "On my Mac I compiled it with :
  g++ ffmpeg_snd.cpp -o ffmpeg_snd -D_GNU_SOURCE=1 -D_THREAD_SAFE -I/usr/local/include/opencv -I/usr/local/include -I/usr/local/include/SDL -Wl,-framework,Cocoa ...."

  But I must use MSVS2010 (I have working project). Ok, I installed mingw to try, but still don’t know what could replace "framework,Cocoa".

  Give me please links to WORKING examples OpenCV+anysoundplayer on Win32 or help me port Karl’s example at least.