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Perceptual Image Compression at Flickr

code.flickr.net

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Re: Perceptual Image Compression at Flickr

#2

Post by brianshaler »

What they did was super impressive, and is a fascinating way to figure out the optimal global compression settings. However, I got my hopes up that perceptual image compression might be about computer vision. At scale, analyzing every image would obviously be prohibitively expensive, but it would be amazing to analyze the detail/edges or color usage (e.g. how much red) in a photo, and tune the q & chroma values accordingly. That, or compress with multiple settings and analyze the resulting images for noise introduced by artifacts.

Re: Perceptual Image Compression at Flickr

#3

Post by __alexs »

> 15% fewer bytes per image makes for a much more responsive experience.

I wonder how they measured this. Seems like perceived speed gains would be sub-linear with file sizes to me. Particularly as actual transfer speed is often too once you factor in network latency patterns.

Re: Perceptual Image Compression at Flickr

#4

Post by Rifu »

Excellent writeup! I'm amazed people signed up to play their test game. Does anyone know if the points you get translate to any sort of other reward, or is a place on the leaderboard more than enough of an incentive to keep playing?

Personally though, I think the linked article about on-the-fly resizing[0] was a more interesting "technical" read.

[0] http://code.flickr.net/2015/06/25/real-time-resizing-of-flic...

Re: Perceptual Image Compression at Flickr

#5

Post by jsjohnst »

Rifu wrote: post #4

Excellent writeup! I'm amazed people signed up to play their test game. Does anyone know if the points you get translate to any sort of other reward, or is a place on the leaderboard more than enough of an incentive to keep playing? Personally though, I think the linked article about on-the-fly resizing[0] was a more interesting "technical" read. [0] http://code.flickr.net/2015/06/25/real-time-resizing-of-flic...

As someone who participated in an earlier iteration of this, I can answer that there was no "prize" (I don't think there was even a leaderboard on the first iteration of this). I can't speak for everyone, but I participated mainly for two reasons, 1) to make sure a crappy compression didn't eventually effect my images I posted there 2) the geek challenge of finding which image was compressed

Re: Perceptual Image Compression at Flickr

#6

Post by brianshaler »

__alexs wrote: post #3

> 15% fewer bytes per image makes for a much more responsive experience. I wonder how they measured this. Seems like perceived speed gains would be sub-linear with file sizes to me. Particularly as actual transfer speed is often too once you factor in network latency patterns.

I agree that with mobile, latency is usually a far bigger factor than throughput when it comes to perceived speed. I would also wonder if, once the image is downloaded, what the performance cost or benefit would be of more compressed images. Are they faster due to a smaller footprint? Or are they more costly to the CPU to decompress? (I would assume the former for JPG, while the latter is often the case with video)
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