`zune-jpeg` 2x slower than `image` crate on my M1 MacBook

[emilk]

I am really intrigued by zune-image based on its compilation time and boasted speed, but my first impression is that it is much slower than the image crate.

I am decoding 1440 × 1920 RGB JPEGs. image takes around 17 ms to decode a 1440 × 1920 RGB JPEG, while zune-jpeg takes around 33ms. I am NOT using the jpeg_rayon feature of image.

Here is one of the images that decodes slowly:

(the image comes from saving frames of videos from https://github.com/google-research-datasets/Objectron)

[etemesi254]

hi it's because our idct is not vectorized but jpeg decoder contains one, there was some effort to address that and there was a branch which achieved that , I was to manually merge it but time became an issue, and I don't have the hardware to test it

[etemesi254]

Merged neon optimized idct to dev branch which should improve decode times considerably for Arm Neon chips.

I can't really test by how much, but would love if you could report speeds on your side

[emilk]

I'm sorry, my original number were bad somehow. I've now done better measurements and I've found this:

• image: 15.6 ms per jpeg
• zune-jpeg 0.3.17: 10.3 ms per jpeg
• zune-jpeg dev branch: 8.2 ms per jpeg

I also measured in Firefox when compiling to WASM:

• image: 35 ms per jpeg
• zune-jpeg 0.3.17: 29 ms per jpeg
• zune-jpeg dev branch: 29 ms per jpeg

So: seems like I'm switching to zune-jpeg 🤘😃

[etemesi254]

good to hear that

WASM speeds can be improved with using wasm intrinsics, If I happen to have time I may implement it but no promises there :)