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• FFMPEG waveform transparent, background solid color

  11 mai 2016, par user1152226

  I am trying to generate a waveform with ffmpeg, I want the background to be a solid color, and the actual waveform to be transparent. The following achieves partially what i want, except that in has a black background. I would like to be able to change this to any color, but have the waveform be transparent. How can i achieve this with ffmepg ?

  ffmpeg -i input.mp3 -filter_complex \
  
  "[0:a]aformat=channel_layouts=mono,\
  
  compand=gain=-6, \
  
  showwavespic=s=600x120, \
  
  colorchannelmixer=rr=1:gg=0:bb=0:aa=1,\
  
  drawbox=x=(iw-w)/2:y=(ih-h)/2:w=iw:h=1:color=red,\
  
  format=rgba,\
  
  colorkey=#ff0000" \
  
  -vframes 1 output.png

  This generates this waveform : the background is black, the waveform itself is transparent. How do I change the background color to a different color, while still keeping the waveform transparent ?

  

• There is a problem with converting ffmpeg video from hev1 to hvc1

  18 septembre 2024, par sixawnstar

  ffmpeg -i in.mp4 -c:v copy -c:a copy -tag:v hvc1 out.mp4

  


  I used ffmpeg to transcode the videos, but some of the transcoded videos were black screens with audio but no visuals.

  


  enter image description hereenter image description here

  


  By using ffmpeg -i video.mp4 to view the video information, it was found that the information for both videos is consistent. However, the screen in Figure 1 displays a black screen after transcoding, whereas Figure 2 functions normally after transcoding.

  


• ffmpeg - when scaling, how to keep shapes of people's heads

  19 janvier 2017, par Dave

  Ok, I’m quite familiar with FFMPEG utility in general, and have used it for
  years to cut short snippets from videos, etc. But it’s only in the last
  month that and I decided to learn to use it to transcode with video-filters
  etc. (Before that, I was using other tools such as ’Handbrake’ and ’FreeMake’
  and VLC, etc.)

  For my ffmpeg transcodes, my target output resolution will always be constant, from one transcode run to the next. But the resolution and display aspect-ratio of the input file, from one transcode run to the next, will vary...could be almost any values.
  The input files will never already have black-bars when displayed.

  So, the relevant portion [ i.e. the video-filter(s) part) of my cmd line ] presently is as follows :

  ffmpeg ... -vf "scale=720:406,setsar=1,pad=720:506:0:40:Black" ...

  Also note : I do NOT use the "-aspect" option in the cmd-line. (Maybe I’ll
  need to (???) to solve my issue, but I’m unsure about how that interacts
  with scaling.)

  ( EDIT : Oh, I happen to have chosen that resolution value of 720x406, for
  the image-area (i.e. inside the top/bottom black bars) because it
  has an aspect ratio of 16:9 (Of course, 16:9 ratio is common these days. )

  My cmd always executes cleanly and produces an output file (a WebM, tho I doubt
  that container types and/or vcodec choices matter at all to scaling algorithm issues).

  So the issue/problem that I’m trying to solve is how to prevent any stretching
  in either direction. In other words, a round soccer ball in the input file
  must yield a round ball in the output file ! (NOT oval-shaped in either axis).

  ( Edit #2 : Oh, I forgot to mention that I’m not have the same amount of stretching from one ffmpeg output file to the next. Sometimes there is
  no stretch in my output file, and with some other input file, the
  people are too tall in the output, and some other output file will have
  people are too wide. I’m assuming
  there is some single cmd that will always work for each randomly sized
  input file, WITHOUT having to resort to examining meta-data of each
  input and then having to adjust portions of the needed ffmpeg cmd.
  I assume this because I have used a tool called "FreeMake" that needs
  no such adjustment. When you do a ’scale’ with that program, it asks
  you to choose one of four adjustment-algorithms labeled "original"
  "stretched", "zoom..." and "auto". If I recall correctly, it was the
  "auto" choice that prevented any stretching.)

  The goal of that last filter (i.e. the "pad=720:506:0:40:Black" phrase) is to
  add a black bar of 40 pixels to the top and 60 pixels to the bottom.
  (That filter IS producing the black-bands, as desired. I mention it,
  because I’m unsure whether it could be having any effect on the altered
  shape of the ’round soccer ball’). If the "pad" filter IS part of the
  issue, then maybe I’ll need to make multiple ffmpeg cmds to achieve
  my overall goal (!?!?). [I’d LIKE to be able to do everything in just
  one ffmpeg cmd, as shown.]

  OK ?

  So are there any image-processing and ffmpeg gurus out there that
  know how to fix my problem ?

  TIA...

  Dave