if your setup supports h264 (more info below), you may enable
playback with the sabr protocol, drastically improving playback start times,
but at a requirement of better hardware.
just like in html5, flash sabr be used if the exp_sabr flag is enabled.
--> yt2009 flags
flash sabr is highly experimental, so you may come across some issues.
if you find - for example - a video that doesn't start at all with sabr,
report an issue over at yt2009 github!
you can now enable h264 mp4 playback within the flash player.
h264 lets you start playing videos way quicker and enables HD support.
h264 may not be supported depending on your browser, OS and the picked video player.
if flash player doesn't show up on watchpages but works everywhere else, you can try
the compatibility fixes listed below. years in brackets indicate the players those settings
will have an effect on.