Tamas Nagy

In my field, systems biology, it’s pretty common to take time-lapse movies to get the dynamics of how the system behaves. And we like showing them off. This makes Google Slides¹ inability to embed videos (without uploading them to Youtube) pretty annoying and inconvenient. Slides does, on the other hand, have good support for embedding GIFs. I came up with the following pipeline (based on notedible’s comment on Stackoverflow). First, make sure to install libav and imagemagick. On Debian-based systems, you can run

sudo apt-get install libav-tools imagemagick

and on MacOS² the easiest way to install them is via homebrew. Then I use the following command to create the GIF:

cat some_movie.m4v | avconv -i pipe: -r 10 -f image2pipe -vcodec ppm - | convert -delay 5 -loop 0 - gif:- | convert -layers Optimize - output.gif

where some_movie.m4v is the video file. This creates an optimized GIF version called output.gif, which you can then upload to Google Slides. The last niggle is that the GIFs play continuously and sometimes it’s helpful to be able to stop/start the playback. Enter the Toggle Animated Gifs extension for Firefox (I’m sure there’s something comparable for Chrome), which lets you do just that.

Addendum 17-04-28

If you get an error that looks like the following with some weirdly formatted .mov files:

avconv version 12, Copyright (c) 2000-2016 the Libav developers
  built on Mar  6 2017 22:35:59 with Apple LLVM version 8.0.0 (clang-800.0.42.1)
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fc78b000000] stream 0, offset 0x30: partial file
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fc78b000000] Could not find codec parameters (Video: mpeg4 (Simple Profile) [mp4v / 0x7634706D]
      none, 1958 kb/s)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'pipe:':
  Metadata:
    major_brand     : qt
    minor_version   : 537199360
    compatible_brands: qt
    creation_time   : 2015-05-26 19:04:15
  Duration: 00:00:10.00, bitrate: N/A
    Stream #0:0(eng): Video: mpeg4 (Simple Profile) [mp4v / 0x7634706D]
      none, 1958 kb/s
      600 tbn (default)
    Metadata:
      creation_time   : 2015-05-26 19:04:15
      handler_name    : Apple Alias Data Handler
      encoder         : MPEG-4 Video
Output #0, image2pipe, to 'pipe:':
Output file #0 does not contain any stream
convert: no decode delegate for this image format `' @ error/constitute.c/ReadImage/509.
convert: no images defined `gif:-' @ error/convert.c/ConvertImageCommand/3254.
convert: no decode delegate for this image format `' @ error/constitute.c/ReadImage/509.
convert: no images defined `output.gif' @
error/convert.c/ConvertImageCommand/3254. 

Then installing the qtfaststart³ Python package via pip install qtfaststart and then running

qtfaststart bad_movie.mov good_movie.mov

should fix the problem and now you can use good_movie.mov with the previous commands to create all the gifs. So apparently what is happening is that some recording software puts the mdat block prior to the moov block (the structural metadata). This is more convenient for recording since the structure isn’t known till the recording is finished, however for playback it isn’t as nice. qtfaststart fixes this by swapping the two blocks:

$ qtfaststart -l bad_movie.mov
ftyp (32 bytes)
wide (8 bytes)
mdat (2448358 bytes)
moov (998 bytes)

while

qtfaststart -l good_movie.mov
ftyp (32 bytes)
moov (998 bytes)
wide (8 bytes)
mdat (2448358 bytes)