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• FFMPEG : Combine "Create video from images" + scale to x + add audio + overlay logo

  7 janvier 2020, par Thomas Wild

  I´m working on a webcam-project. It is for generating timelapse videos of sunset/sundown.

  I´m using a raspberrypi to generate them with gphoto2 + DSLR.

  At the end of the day the images should get to an video, with audio and an overlay logo.
  And it should be scaled to 1920 pixel.
  I got a nice solution an it worked.

  1. Producing the timelapse video an scale it :

     ffmpeg -y -framerate 25 -start_number 0000001 -i /var/www/html/webcam/2020-01-05_bilder/%7d.jpg -vf scale=1920:-1 -pix_fmt yuv420p /var/www/html/webcam/2020-01-05-tag-output-1920.mp4

  2. Taking the output of (1) and add an overlay-logo, add audio

     ffmpeg -y -i '/var/www/html/webcam/2020-01-05-tag-output-1920.mp4'
-i '/var/www/html/webcam-scripts/graphics/logo.png'
-i '/var/www/html/webcam-scripts/sounds/chill_time_5.mp3'
-shortest -filter_complex '[1][0]scale2ref=h=ow/mdar:w=iw/6[#A logo][liebfrauen]; [#A logo]format=argb,colorchannelmixer=aa=0.95[#B logo transparent]; [liebfrauen][#B logo transparent] overlay=(main_w-w)-(main_w*0.05):(main_h-h)-(main_h*0.01)'
-c:v libx264 -crf 18 -preset slow -pix_fmt yuv420p -c:a aac -strict -2
'/var/www/html/webcam/2020-01-05-tag-1920.mp4

  I tried to combine both actions, but I get an error :

  ffmpeg -y -framerate 25 -start_number 0000001 -i '/var/www/html/webcam/2020-01-05_bilder/%7d.jpg' -vf scale=1920:-1 -pix_fmt yuv420p -i '/var/www/html/webcam-scripts/graphics/logo.png' -i '/var/www/html/webcam-scripts/sounds/chill_time_5.mp3' -shortest -filter_complex '[1][0]scale2ref=h=ow/mdar:w=iw/6[#A logo][liebfrauen]; [#A logo]format=argb,colorchannelmixer=aa=0.95[#B logo transparent]; [liebfrauen][#B logo transparent] overlay=(main_w-w)-(main_w*0.05):(main_h-h)-(main_h*0.01)' -c:v libx264 -crf 18 -preset slow -pix_fmt yuv420p -c:a aac -strict -2 '/var/www/html/webcam/2020-01-05-tag-1920.mp4'

  Error : Filtergraph ’scale=720 :-1’ was specified through the -vf/-af/-filter option for output stream 0:0, which is fed from a complex filtergraph.
   vf/-af/-filter and -filter_complex cannot be used together for the same stream.

  Isn`t it possible to combine these inputs and scale it ? Or ... Where is my misunderstanding ?

• Clip long video segment quickly

  30 janvier 2020, par PRMan

  Let’s say I have a video called Concert.mp4. I want to extract a performance from it quickly with minimal reencoding. I want to do the equivalent of this, but faster :

  ffmpeg -i "Concert.mp4" -ss 00:11:45 -to 00:18:15  -preset veryfast -y artist.mp4

  This takes 17 seconds, which is way too long for our needs.

  Now, it turns out that 11:45 and 18:15 don’t fall on iframes, so if you try this you will get a 3 second delay at the beginning before the video shows :

  ffmpeg -i "Concert.mp4" -ss 00:11:45 -to 00:18:15 -c copy -y artist.mp4

  Running this command, we can see where we need to cut :

  ffprobe -read_intervals "11:00%19:00" -v error -skip_frame nokey -show_entries frame=pkt_pts_time -select_streams v -of csv=p=0 "Concert.mp4" > frames.txt

  So what we need to do is encode the first 3.708 seconds, copy the middle, and then encode the last 5.912 seconds.

  I can get the 3 segments to all look perfect (by themselves) like this :

  ffmpeg -ss 698.698 -i "Concert.mp4" -ss 6.302 -t 3.708 -c:v libx264 -c:a copy -c:s copy -y clipbegin.mp4
  
  
  
  ffmpeg -ss 708.708 -to 1089.088 -i "Concert.mp4" -c copy -y clipmiddle.mp4
  
  
  
  ffmpeg -ss 1089.088 -i "Concert.mp4" -t 5.912 -c:v libx264 -c:a copy -c:s copy -y clipend.mp4
  
  
  
  ffmpeg -f concat -i segments.txt -c copy -y artist.mp4

  segments.txt of course contains the following :

  file 'clipbegin.mkv'
  
  file 'clipmiddle.mkv'
  
  file 'clipend.mkv'

  I saw this solution presented here, but no amount of tweaking gets it to work for me :

  https://superuser.com/a/1039134/73272

  As far as I can tell, this method doesn’t work at all. It crashes VLC pretty hard no matter what I try.

  The combined video keeps glitching after the 3 seconds, probably because the PTS times are different or something (using some options, I have seen warning messages to this effect). Is there anything I can add to the commands above to get this to work ? The only requirement is that the middle command must not re-encode the video, but must do a fast copy.

  Thanks in advance.

• FFmpeg : Add alpha channel to a video using a PNG mask

  7 avril 2016, par Rodrigo Polo

  I saw that FFmpeg can merge/blend two videos with alpha channel and can encode video with alpha channel using the qtrle codec, but, It is possible to apply a PNG file mask, either a black and white or a PNG with an alpha channel to a video in order to have a video with the alpha channel of the PNG applied ?

  Here is the concept in images

  Original video :
  

  PNG file with alpha channel, the "mask" :
  

  And the result :
  

  Or even a black and white image as a mask for alpha channel :
  

  Any help would be appreciated, thank you !