Updating MSE/video duration after playlist change

[phillipseamore]

I'm trying to seamlessly and smoothly switch from a short window DVR to a longer window and I can't seem to find a method to update the MSE/video duration to reflect the change.

For this I'm simply replacing the window lengths defined in my playlist URL's:

hls.stopLoad();
hls.url = hls.url.replace('600','3600'); // https.//example.org/dvr/stream-600.m3u8 changes to stream-3600.m3u8
for(var level of hls.levels) {
    level.url = level.url.replace(600, 3600);
}
hls.startLoad(); 

This works fine, no hiccups in playing and the 3600 second playlists are being fetched and I see that all fragments are in level.details - however I'm left trying to find a solution to force an update to the MSE seekable buffer (and the video's duration).

[phillipseamore]

It seems there's no way to prepend to a buffer in MSE without going to a whole lot of effort (e.g. you can't shift the timestamps to move the already existing sourcebuffer without remuxing etc). So I'll stick with my loadSource switching and a fake progressbar.