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Re^2: Specialized data compression

by wanna_code_perl (Pilgrim)
on Sep 16, 2012 at 16:37 UTC ( #993930=note: print w/replies, xml ) Need Help??

in reply to Re: Specialized data compression
in thread Specialized data compression

These suggestions were helpful. Thank you! Using deltas for x,y,z did help quite a bit.

The time delta derivative approach was interesting to think about, but would basically break the lossless compression I have going. At the moment, at least, I need to be able to reconstruct the original input verbatim, and the only way to do that is with fixed point arithmetic.

The one concession I was able to safely (verifiably) make is quantizing the time deltas that are close to the sensor frequency. The clock has a large (+/- 15%!) but predictable jitter pattern I was able to isolate and then basically RLE the result.

With the latest optimizations, I'm sitting at about 9:1 compression, which is acceptable. I was shooting for 10:1, but that last 33 KiB won't come easy.

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[Corion]: Ouch. I just learned something about Chrome - the "version numbers" are not really feature numbers... Chrome 62 still gets new features even though Chrome 64 is out and Chrome 65 is the dev version
[erix]: why ouch? Something to be said for that ,surely?
LanX is a dev version
[marto]: That reminds me, I made some notes somewhere with regard W::M::C, I'll get round to a PR when I've time to flesh it out
[Corion]: erix: But that makes for fun bug hunting. "What version of Chrome are you running?" "v62". "I also run v62 and it works on my machine". :-(
[Corion]: marto: Great, looking forward to the PR!

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