can not switch down level sometimes when limit network speed

[aidaima]

dear mangui, i have no ideal about why add checker at https://github.com/mangui/flashls/blob/dev/src/org/mangui/hls/loader/FragmentLoader.as#L183 when switch down level. I have a problem that level can not switch down sometimes even if network speed has been limited below 10K(current is 800k and also have 400k, at that time it cound not switch from 800K down to 400K).

[mangui]

Hi @aidaima before performing emergency switch down, flashls tries to flush current loaded fragment from StreamBuffer. flashls buffer has two layers : a software buffer (StreamBuffer class) and Flash buffer (NetStream) if current loaded fragment has already been pushed (even partially) into Flash buffer (NetStream), it means that some frame of this fragment might already have been played ... emergency switch down might generate some glitches in that case ... this is problematic, as flashls tries to keep this emergency switch down smooth. => flashls only allows emergency switch down in case current loaded fragment has not yet been pushed to NetStream (i.e. its tags are in StreamBuffer only) => when your current buffer is really low, you cannot emergency switch down smoothly.