On the first play, youtube videos will now synchronize to gameplay a little better. There is a small tradeoff though -- your machine will need to build its own synchronization file for youtube videos even if others have already played them. It won’t need to do that for youtube songs you’ve previously played though (even before this update).
The way it used to work is that synchronization files (yash files) could be shared and your game would use a shared one when you played a youtube song for the first time. The shared file would usually synchronize just right, but would occasionally be noticeably off. Then, during your first play, a more perfect sync file was generated in the background to be used for future plays. Now, the optimal sync file is generated before your first gameplay session with a video.
For local song files, like the recommended songs tab and your own MP3s, this doesn’t change anything.
There’s a new launch option to revert this change and go back to the old way of sharing yash files if you'd like:
+allowsharedyashfiles