One of the issues people face when running a custom ROM is that whenever the latest updates are released it usually consists of a zip file 100 MB or larger. This might not be a problem if you are using your own Wi-Fi network at home but when you are on the go and there’s no fast mobile data available getting that update may be quite frustrating. Several things could go wrong such as the download stops all of a sudden or worse the file downloaded is corrupted.
“We all love to get those updates to our devices, but sometimes it becomes tedious to get an update that is 100MB+ over non-WiFi connections, or some of you start to get the jitters if you have to wait to download that new version. To that end, and because we needed a reliable update system built into the project, Chainfire set out to create OpenDelta.”
Those running OmniRom on their devices will no longer experience these issues as a new feature called OpenDelta has been announced by developer Chainfire. As the name suggests, the system uses open deltas whenever possible to reduce the download size of the update.
“OpenDelta provides automatic OTA updates for nightly builds, making use of deltas when possible, to reduce the size of the download using binary differentials (VCDIFF, RFC 3284) between the previous and the current release, courtesy of xdelta3. The produced delta files are pushed to the public download server, and the current build is saved to a private location to serve as input for the next differential run.”
Basically this means that only the updates that are not on your device will be downloaded.
An Android client on the device checks in with the download server and gets the .delta file for its current build. It will then be able to determine the name of the next build and the build after that. So in case you don’t update for a number of builds it will still be able to reconstruct the latest build by chaining the deltas.
OpenDelta can be accessed from the System Update menu in the About menu of System Settings. You also have the option to assign which network to choose to automatically let OpenDelta check for the updates.
Right now OpenDelta is still under development and will most probably hit a few snags once it is released due to the broad range of devices it will have to support.
OmniRom is a custom ROM designed to run on Android devices and is made to be different.