This new release requires you to reanalyze all tracks you have on your phone. There are two reasons for this.
Firstly, a new, much sharper, beatgraph visualization has been developed. The beatgraphs are now computed directly from mp3 frames, which is somewhat faster than sending the entire audio stream through a decoder and then a filter bank. In the past it was possible to map the new beatgraphs back to the old blurrier beatgraphs. However, the opposite is not possible. we cannot make the blurrier beatgraphs sharper if they have been analyzed with the old routines. And since we like the new visualization a lot better, we decided to get rid of the old algorithms. Therefore, there is no easy way out but to reanalyze everything.
A second reason why a reanalysis is necessary is because BpmDj now also measures for each song the energy content of 32 frequency bands. In the past, only 3 bands were used. That results in better loudness estimates and a better detection of nearest neighbors. But again, mapping the old feature vectors to the new ones is not possible.
Aside from providing a totally new analysis back-end, we also got rid of the SQLite database that stored the data. The main reason for this is that object oriented languages don't map very well to relational databases. BpmDj now contains a self developed database based on a journalling, transactional memory. It has garbage marking, compaction and page management to reclaim unreachable memory. All technically very interesting, yet it means that a rescan of the entire file system should be performed. Writing a converter from the SQL rows to our own was just too time consuming. More information on the current database is available here
To perform the upgrade
Q: Will my mixes still be available after the upgrade
A: Yes they should, after reanalysis of all tracks. Up to then the mixes will contain songs with two orange icons (one to notify that the mp3 is lacking. The other to notify that the beatgraph is not there either).