user12276: I have seen this and this post explaining how to crop and stack videos using ffmpeg.
My question is - is there an easy (preferably one step) way to turn a horizontally stacked video into a vertically stacked one?
And is there a Linux-way to re-encode given 3D video formats into others?
Edit:
with Mulvyas help I wrote a script which does the converting stuff and creates a text file with meta information needed by the Gear VR video player.
Note: you need a recent version of ffmpeg for the vstack filter - version 2.6 which is installed with Fedora 22 is too old. Version 2.8.3 has vstack available.

user1871: Just integrate all filtering into one command:
ffmpeg -i input.mp4 \
-filter_complex "[0:v]crop=in_w/2:in_h:0:0 [top]; \ 
[0:v]crop=in_w/2:in_h:in_w/2:0[bottom]; \
[top][bottom]vstack[outv]" \
-map "[outv]" -map 0:a -c:a copy output_3dv.mp4

Edit: this command below scales and pads the output to 2000x2000
ffmpeg -i input.mp4 \
-filter_complex "[0:v]crop=in_w/2:in_h:0:0 [top]; \
[0:v]crop=in_w/2:in_h:in_w/2:0[bottom]; \
[top][bottom]vstack,\
scale=iw*min(2000/iw\,2000/ih):ih*min(2000/iw\,2000/ih), \
pad=2000:2000:(ow-iw)/2:(oh-ih)/2[outv]" \
-map "[outv]" -map 0:a -c:a copy output_3dv.mp4


12276: <p>I have seen <a href="https://stackoverflow.com/a/33764934">this</a> and <a href="https://video.stackexchange.com/questions/4563/how-can-i-crop-a-video-with-ffmpeg?newreg=08cf71ca624344a09f50ef640118e6cd">this</a> post explaining how to crop and stack videos using <code>ffmpeg</code>.</p>

<p>My question is - is there an easy (preferably one step) way to turn a horizontally stacked video into a vertically stacked one?</p>

<p>And is there a Linux-way to re-encode given 3D video formats into others?</p>

<p><strong>Edit:</strong></p>

<p>with Mulvyas help I wrote a <a href="https://github.com/frans-fuerst/magic/raw/master/LR2TB.py" rel="nofollow noreferrer">script</a> which does the converting stuff and creates a text file with meta information needed by the Gear VR video player.</p>

<p>Note: you need a recent version of <code>ffmpeg</code> for the <code>vstack</code> filter - version 2.6 which is installed with Fedora 22 is too old. Version 2.8.3 has <code>vstack</code> available.</p>
 1871: <p>Just integrate all filtering into one command:</p>

<pre><code>ffmpeg -i input.mp4 \
-filter_complex "[0:v]crop=in_w/2:in_h:0:0 [top]; \ 
[0:v]crop=in_w/2:in_h:in_w/2:0[bottom]; \
[top][bottom]vstack[outv]" \
-map "[outv]" -map 0:a -c:a copy output_3dv.mp4
</code></pre>

<p>Edit: this command below scales and pads the output to 2000x2000</p>

<pre><code>ffmpeg -i input.mp4 \
-filter_complex "[0:v]crop=in_w/2:in_h:0:0 [top]; \
[0:v]crop=in_w/2:in_h:in_w/2:0[bottom]; \
[top][bottom]vstack,\
scale=iw*min(2000/iw\,2000/ih):ih*min(2000/iw\,2000/ih), \
pad=2000:2000:(ow-iw)/2:(oh-ih)/2[outv]" \
-map "[outv]" -map 0:a -c:a copy output_3dv.mp4
</code></pre>
