user23324: I have a 30fps video that is 234 minutes long and want to shrink it down to 2 minutes.  1-(234-2)/234) gives me 0.0085 which I use 
ffmpeg -i source.mp4 -vf setpts=PTS*0.0085,palettegen palette.png 
followed by 
ffmpeg -i source.mp4 -i palette.png --filter_complex setpts=PTS*0.0085,paletteuse survey.gif
Actually making the gif is excruciatingly slow compared to extracting the desired frames into a massive directory of png's which I can then combine with convert into a gif.  Aside from my main question, it doesn't seem like ImageMagick's convert supports user supplied palette files.
I understand that PTS is just adjusting how long a single frame is shown in a video but setpts has felt like the only reliably precise way of cutting the source.mp4 down.  
I looked at framestep and it is much better for speed but I couldn't figure out an ideal value for framestep that wouldn't make the resulting gif step from one frame to the next like what I would get from using convert and a delay of 0.5 between frames.
Aside from above, these survey are meant to quickly scan through hours of video for various points of concern in a gif format able to be uploaded privately to imgur or giphy so others on my team could review them remotely and without ftp/dropbox/etc.

user1871: Assuming you want a 30 fps 2.5m GIF, use
ffmpeg -i source.mp4 -vf "select='not(mod(n,trunc(234/2.5)))',palettegen" palette.png

and
ffmpeg -i source.mp4 -i palette.png -filter_complex "[0]select='not(mod(n,trunc(234/2.5)))',setpts=N/30/TB[v];[v][1]paletteuse" survey.gif


23324: <p>I have a 30fps video that is 234 minutes long and want to shrink it down to 2 minutes.  <code>1-(234-2)/234)</code> gives me 0.0085 which I use </p>

<p><code>ffmpeg -i source.mp4 -vf setpts=PTS*0.0085,palettegen palette.png</code> </p>

<p>followed by </p>

<p><code>ffmpeg -i source.mp4 -i palette.png --filter_complex setpts=PTS*0.0085,paletteuse survey.gif</code></p>

<p>Actually making the gif is excruciatingly slow compared to extracting the desired frames into a massive directory of png's which I can then combine with <code>convert</code> into a gif.  Aside from my main question, it doesn't seem like ImageMagick's convert supports user supplied palette files.</p>

<p>I understand that PTS is just adjusting how long a single frame is shown in a video but setpts has felt like the only reliably precise way of cutting the source.mp4 down.  </p>

<p>I looked at <code>framestep</code> and it is much better for speed but I couldn't figure out an ideal value for <code>framestep</code> that wouldn't make the resulting gif step from one frame to the next like what I would get from using <code>convert</code> and a delay of 0.5 between frames.</p>

<p>Aside from above, these survey are meant to quickly scan through hours of video for various points of concern in a gif format able to be uploaded privately to imgur or giphy so others on my team could review them remotely and without ftp/dropbox/etc.</p>
 1871: <p>Assuming you want a 30 fps 2.5m GIF, use</p>

<pre><code>ffmpeg -i source.mp4 -vf "select='not(mod(n,trunc(234/2.5)))',palettegen" palette.png
</code></pre>

<p>and</p>

<pre><code>ffmpeg -i source.mp4 -i palette.png -filter_complex "[0]select='not(mod(n,trunc(234/2.5)))',setpts=N/30/TB[v];[v][1]paletteuse" survey.gif
</code></pre>
