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• Most efficient way for ffmpeg to make thumbnails ? [Windows 10]

  26 janvier 2017, par gregm

  I normally use ThumbnailMe to make contact sheets of thumbnails. My default setting is 15 rows x 5 columns, so 75 images, in videos that are anywhere from 45 minutes to around 90 minutes. ThumbnailMe makes a contact sheet of this size virtually instantaneously. A recent requirement to make a LOT of contact sheets for a LOT of videos has me looking at a command line option so I can do these in batches. I’ve tried a couple different ways to make the thumbnails from the command line :

  ffmpeg -ss 300 -i myvideo.avi -vf fps=1/300 %d.jpg

  or

  ffmpeg -i myvideo.avi -vf fps=1/60 %d.jpg

  No matter which of these methods I use it takes roughly a minute to make just 16 screenshots (from there I would use ImageMagick to make the contact sheet). As I said above, ThumbnailMe can make a 15x5 grid of images at the mere press of a button. ThumbnailMe is built on an older command line program, Movie Thumbnailer, which I think used an old version of ffmpeg, or at least the codec libavcodec.

  If these other programs can create thumbnails so quickly why does it take ffmpeg so long to make them for me ? Even if I output the screenshots in a very small size, say 50x50, it still takes 2 secs for each image to be created.

• Adding the Transform video filter to ffmpeg

  1er août 2016, par aaeim

  first off I’m new to ffmpeg, and stackoverflow. so sorry If I’m doing something wrong.

  Earlier I commented on a post related to this but it got deleted because it was not an answer or something. So I’m asking my own question here.

  I followed this instructions https://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu

  up untill Unzipping the ffmpeg file. Then I followed the facebook instructions

  1. Checkout the source for ffmpeg
  2. Copy vf_transform.c to the libavfilter subdirectory in ffmpeg source
  3. Edit libavfilter/allfilters.c and register the filter by adding the line : REGISTER_FILTER(TRANSFORM, transform, vf) ; in the video filter registration section
  4. Edit libavfilter/Makefile and add the filter to adding the line : OBJS-$(CONFIG_TRANSFORM_FILTER) += vf_transform.o in the filter section
  5. Configure and build ffmpeg as usual

  and finally I ran the remaining instructions from the compilation guide.

  I did the whole process a couple times but The result is always the same when I try to test.

  ffmpeg version N-80901-gfebc862 Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  
    configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --mandir=/usr/share/man --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libfreetype --enable-gnutls --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvidstab
  
    libavutil      55. 28.100 / 55. 28.100
  
    libavcodec     57. 48.101 / 57. 48.101
  
    libavformat    57. 41.100 / 57. 41.100
  
    libavdevice    57.  0.102 / 57.  0.102
  
    libavfilter     6. 47.100 /  6. 47.100
  
    libavresample   3.  0.  0 /  3.  0.  0
  
    libswscale      4.  1.100 /  4.  1.100
  
    libswresample   2.  1.100 /  2.  1.100
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Unknown filter 'transform'.

  I’m on elementary OS.
  Thx and sorry if the post is all wrong.

• How to preserve transparency when using png to make video with ffmpeg

  27 septembre 2016, par Ryan James

  I have a series of png’s that have an alpha channel as a background. Each file is named like file_name.0001.png and so on, in subsequent order. I’d like to join these png’s into a video with ffmpeg and maintain the transparency.

  I’ve tried a couple of things but I suspect I’m running into a codec issue. When I run ffmpeg, the video is created but the background is black.

  If it makes a difference, I’m wanting to use the video in Microsoft Powerpoint. Thanks !

  Edit
  The suggested duplicate is very close to what I was looking for, thank you ! The only reason it’s not a complete solution is none of the options presented in the other thread work well with Microsoft Powerpoint. None of the codecs used in the suggested solution play well with Powerpoint. This is not the fault of ffmpeg, but of Powerpoint.

  Though ffmpeg doesn’t seem to be able to do what I need, I found that imagemagick did the trick. I was able to create a gif from the images and the alpha channel was preserved. I used the following :

  convert -dispose 3 -coalesce images.*.png gif_file_name.gif

  The -dispose 3 is critical as it tells imagemagick to clear the image prior to overlay, otherwise, you can see each image overlaid on each other (since they have the transparent background).