On Wed, 16 May 2012, Matthew Wilcox wrote:
First off I know that a number of people say this is not possible. I
am not wanting to argue this because I don't have the knowledge to
argue it - but I do want to understand why, and currently I do not.
Please also remember that I can only see this from an authors
perspective as I'm ignorant of the mechanics of how these things work
internally.
The idea is to have something like:
<link media="min-bandwidth:0.5mps" ... />
<link media="min-bandwidth:1mps" ... />
<link media="min-bandwidth:8mps" ... />
Without going deeper into the specific points, implementation experience
suggests that even implementing a binary low-bandwidth/high bandwidth
detection is extremely difficult; Opera has one coupled to the UI for the
"turbo" feature and it has been somewhat non-trivial to get acceptable
quality.
In general the problem with trying to measure something like bandwidth is
that it is highly time-variable; it depends on a huge number of
environmental factors like the other users/applications on the same
connection, possible browser features like down-prioritising connections
in background tabs, external environmental features like "the train just
went into a tunnel" or "I just went out of range of WiFi and switched to
3G" and any number of other things. Some of those are temporary
conditions, some are rapid changes to a new long-term state. Trying to
present a single number representing this complexity in realtime just
isn't going to work.
