Change Active Storage’s video preview format from PNG to JPG

[javan]

PNG is not an ideal format for storing video previews for the same reason it’s not ideal for storing photos. We don’t need lossless compression or the associated extra bytes. Switching to JPG results in files that are ~90% smaller and have a negligible difference in image quality.

Before

$ ffmpeg -i beach.m4v -y -vcodec png -vf thumbnail -vframes 1 -f image2 beach.png

$ mediainfo beach.png
Format      : PNG
File size   : 1.78 MiB
Width       : 1 920 pixels
Height      : 1 080 pixels
Bit depth   : 24 bits
Compression : Lossless

After

$ ffmpeg -i beach.m4v -y -vframes 1 -f image2 beach.jpg

$ mediainfo beach.jpg
Format      : JPEG
File size   : 82.2 KiB
Width       : 1 920 pixels
Height      : 1 080 pixels
Bit depth   : 8 bits
Compression : Lossy

---

beach.m4v details

$ mediainfo beach.m4v
Format    : MPEG-4
Codec ID  : M4V  (M4V /M4A /mp42/isom)
File size : 37.4 MiB
Duration  : 20 s 860 ms
Width     : 1 920 pixels
Height    : 1 080 pixels