This appears to be a regression, as I cannot reproduce with 1.5:
```
■ uname -srvmo
Linux 5.6.14-arch1-1 #1 SMP PREEMPT Wed, 20 May 2020 20:43:19 +0000 x86_64 GNU/Linux
■ LC_ALL=C ls -lh 1994.mkv
-rw-r--r-- 1 userx userx 11G May 17 14:50 1994.mkv
■ LC_ALL=C pacman -Qi imlib2 | grep Version
Version : 1.5.1-1
■ time imlib2_view 1994.mkv
Image format not available
real 0m0.011s
user 0m0.005s
sys 0m0.006s
■ sudo pacman --noconfirm -U /var/cache/pacman/pkg/imlib2-1.6.1-2-x86_64.pkg.tar.zst > /dev/null
■ time imlib2_view 1994.mkv
No loadable image
real 0m22.759s
user 0m0.012s
sys 0m4.716s
```
Thank you for maintaining imlib2. It powers my favorite image viewer (feh).