Lepton image compression: saving 22% losslessly from images at 15MB/s

We are pleased to announce the open source release of Lepton, our new streaming image compression format, under the Apache license.

Lepton achieves a 22% savings reduction for existing JPEG images, by predicting coefficients in JPEG blocks and feeding those predictions as context into an arithmetic coder. Lepton preserves the original file bit-for-bit perfectly. It compresses JPEG files at a rate of 5 megabytes per second and decodes them back to the original bits at 15 megabytes per second, securely, deterministically, and in under 24 megabytes of memory.

We have used Lepton to encode 16 billion images saved to Dropbox,

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Pocket watch: Verifying exabytes of data


There is nothing more important to Dropbox than the safety of our user data. When we set out to build Magic Pocket, our in-house multi-exabyte storage system, durability was the requirement that underscored all aspects of the design and implementation. In this post we’ll discuss the mechanisms we use to ensure that Magic Pocket constantly maintains its extremely high level of durability.

This post is the second in a multi-part series on the design and implementation of Magic Pocket. If you haven’t already read the Magic Pocket design overview go do so now;

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