Delta Coding Joshua Joy Nagendra Akula Suresh Babu

Delta Coding Joshua Joy, Nagendra Akula Suresh Babu, Christine Kuo, Hiral Kapadia, Mario Gerla UCLA

Background: Deduplication Duplicate blocks, shown with the same colors, only need to be stored once

Problem: Deduplication Fails on Photos Original State of the art deduplication unable to dedup Black and white transformation

Problem - Unable to Deduce Transformations Original Crop Near duplicate detection locates similar images, though unable to deduce transformations to generate new images

Motivation • Reduce storage space for saving similar images on filesystems • Reduce number bytes transferred when sharing similar images on network

Contribution • Store the original image and calculate the required transformations • On-demand generation of transformed image using lineage from meta file • No loss of image quality

Graph Source Version 1 Version 2 1. 5 MB Receiver wishes to fetch version 2 Transformation 1 1024 bytes Version 1 Receiver can either fetch the slower version 2 or the smaller and faster transformation 1

Lineage Tree (1/2) • /ucla. edu/alice/avengers/image/1280 x 720/alicegalaxyii/2/1280 x 720/alicegalaxyii/1 • /mit. edu/bob/avengers/image/960 x 480/bobiphone 4 s/3/1280 x 720/alicegalaxyii/2 • /ucla. edu/alice/avengers/diff/1280 x 720/alicegalaxyii/2/1280 x 720/alicegalaxyii/1 • /mit. edu/bob/avengers/diff/960 x 480/bobiphone 4 s/3/1280 x 720/alicegalaxyii/2 • Structure o. Owner o. Data Set o. Content type o. Image Size o. Version (Device. Id, Version Number)

Lineage Tree (2/2) • Each node may have local copy of lineage due to network partitions • Merging lineage trees can be reconstructed in n log n time • Lineage tree enables node to decide which versions and transformations to request

Results Our solution stores the initial photo. Then for each similar photo generate a small metafile.

Results Our solution transfers only the metafile for similar images.

Future Work • Compose images from multiple users at an event

Related Work • HTTP delta compression o. Client-side differential patching of static resources o. VCDIFF Generic Differencing and Compression Data Format (rfc 3284) o. Shared Dictionary Compression over HTTP o. Doesn't work for photos!

References • http: //tools. ietf. org/html/rfc 3284 • http: //en. wikipedia. org/wiki/Shared_Dictionary_ Compression_Over_HTTP • https: //github. com/plotnikoff/connect-diffable • http: //www. blogs. zeenor. com/wpcontent/uploads/2011/01/Shared_Dictionary_C ompression_over_HTTP. pdf https: //code. google. com/p/diffable/ http: //www. stevesouders. com/blog/2010/07/09 • •