Choose contextual chat for a talk in a longer session based on video position rather than current time

[mattmccutchen]

The feature that automatically switches the contextual chat channel for each talk in a session is great! However, sometimes I watch session videos a little or a lot behind, so I'd like the channel to be chosen based on my position in the video rather than the current time, if you can possibly do that using the video embedding API. I suppose that if metadata on where the talks start and end in the video were available, it would be possible to do other things like let the user seek to the start of a given talk, although for that case, there's an alternative solution of linking the talk page to a video of the single talk.