> YouTube has to use the User Agent to try to serve videos that the client can actually play.
Why? We have JavaScript feature detection for video tags: http://diveinto.html5doctor.com/detect.html#video-formats
Why? We have JavaScript feature detection for video tags: http://diveinto.html5doctor.com/detect.html#video-formats
I've worked with video format streaming, though, and encountered a situation where there was a driver on a certain Android device manufactured by a major hardware vendor that you've certainly heard of, and their driver silently corrupted video that was using low-latency streaming options. And by "corrupted" I mean that, while a few of the pixels looked almost right, sometimes, it was mostly just garbage and blank grey screens.
I gave them a sample stream that failed, and they verified that yes, it's their fault. And that no, they weren't going to ship an update for it. Sorry. Device had been out for two years. Apparently no one thought to actually test the various standard options in that video codec. It works with the "normal" options? Ship it!
So I totally understand the need to look at UA strings. I had to look for that particular device hardware profile and disable the low-latency streaming options in order for our product to work on that device.
Edit: Not saying that's always correct, but there does seem to be a tension between: "make sure your code can work well, even in a bad environment" and "don't mask bugs, instead fix them where it makes the most sense to do so" (in this case: in the dozens of browsers instead of in millions of websites).
Finding workarounds for browser bugs is a common theme for the work that web developers do. Yes, browser vendors should fix the bugs, but in the meantime, there's no reason to have a bad user experience.
If a mechanism exists to prevent your customer from perceiving this, as a business the smart decision is going to be to use it.
"i'm getting a lot of corrupt unsupported browser when accessing video on other sites, so i'm using chrome. i can't figure out if it's flash or firefox but i'm tired of opening the hood, i'm done with FF for now"
Most of them looked for a workaround and spoofed the user agent, but they are the kind of people that fiddle with settings. Normal users probably either don't notice or change browser.