There's no new app coming for Windows - the web can do everything the app could do, plus a lot more.
A brief technical explanation of the solution:
The video you're watching is split into segments between 4 and 6 seconds long (depending on the platform).
For a live stream, the client is provided a list of segments that updates for each segment, including all segments for the last minute (to allow for buffering).
To allow watch from start / rewind, we provide the client with a "Live to VOD" stream - i.e. instead of just providing the last few segments, it provides all segments back to the start of the stream.
So every 4-6 seconds, the client is downloading a list of the segments which it then has to read and calculate the next segment to play. Some clients do this really well, and it doesn't matter how big the list gets. Other clients get slower and slower as the list grows, and they're so busy processing the manifest that they don't actually have time to download the video segments - causing buffering or dropping of video quality.
We don't have the real-time data to be able to split into specific races in the live stream - we just chop it up afterwards.
Note: live rewind isn't available for MotoGP on any of our platforms for the above reason.
