SH*T!
I had a 1h video, with about 400Mb…
My batch was taking HOURS (with a 8 core CPU) and creating a 5Gb mp4 file of the encoding….. wtf?

13442 www-data 22 2 1426m 361m 3884 R 614 4.5 2180:37 ffmpeg 
14462 www-data 22 2 1773m 966m 3660 R 100 12.1 293:07.12 ffmpeg

I had to run the command manually and figure out the issue.

 Metadata:
 creation_time : 2014-04-19 19:19:31
File 'video.mp4' already exists. Overwrite ? [y/N] y
[mp4 @ 0x26a8ae0] Frame rate very high for a muxer not efficiently supporting it.
Please consider specifying a lower framerate, a different muxer or -vsync 2
[libx264 @ 0x26c6ce0] using SAR=1/1
[libx264 @ 0x26c6ce0] MB rate (108000000) > level limit (2073600)

I had to add -vsync 2 to solve this.

/usr/bin/ffmpeg -i 14-18-14.mp4 -c:v libx264 -vsync 2 -threads 4 video.mp4