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Comment by petercooper | Hacker News Reader

I've been working on a pure Ruby JPEG encoder and a bug led me to an effect I wanted. The output looked just like the "crunchy" JPEGs my 2000-era Kodak digital camera used to put out, but it turns out the encoder wasn't following the zig-zag pattern properly but just going in raster order. I'm now on a quest to figure out if some early digital cameras had similar encoding bugs because their JPEG output was often horrendous compared to what you'd expect for the filesize.

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Quite a lot of hardware devices have broken encoders. I noticed just how inconsistent it is if software will tolerate invalid files or work around it.

Seems these days a there’s more of a preference to outright refuse invalid files since they could be exploit attempts.

The interesting thing about the situation I mentioned is that while the encoding algorithm was wrong, the actual output was valid JPEG that simply didn't look quite visually correct. But you're right, invalid encoding can be a problem too, and I have noticed during testing that a lot of decoders are quite forgiving of it.

Ah yeah that is an interesting case. In my situation, a thermal camera I got was inserting an invalid frame at the start which likely got used by their proprietary program to store data. VLC would view it but most of Mac/iOS would refuse to play the video until I used ffmpeg to delete the invalid frame.

Can you post a screenshot comparison? I'm curious what these "crunchy jpegs" look like

Yes. The size is slightly different here to show it off better, but compare left and right in https://peterc.org/misc/queen.png (both are the same "quality" and file size but the right hand one has incorrect quantization ordering)

Also it turns out it wasn't a Kodak camera, but a Casio QV 10 I had much earlier. You can sorta see what I meant here: https://medium.com/people-gadgets/the-gadget-we-miss-the-cas... .. though the resolution is far lower too. The weird blocky color aberrations aren't just JPEG artefacts but related to the same quantization ordering issue I think.

Oh yes I've seen lots of old images that have that sort of feel. I always assumed it was because of poor sensor quality or something

My assumption also, but once this thing spat out those images by accident, I started to wonder if maybe broken code ended up in the firmware of these cameras and just.. stayed there :-D Might be a fun project one day if I can get hold of one and rip out the firmware!

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