Comment by kllrnohj

They ship with hardware jpeg decoders because they ship with hardware jpeg encoders for camera capture latency reasons and it turns out you can basically just run that hardware in reverse.

The SoCs aren't investing more than a token amount of effort into those jpeg decoders, and from experience some of them claim to exist but produce the shittiest looking output imaginable and more slowly than jpeg-turbo at that.

Also you can trivially find out if your Android phone is doing this or not, just run some perf call sampling while decoding jpegs. If all you see is AOSP libraries & libjpeg-turbo, well then they aren't doing hardware decodes :)