if the video quality rule configurable?

There are 4 video quality as : “low bandwidth”, “low definition”, “standard definition”, “high definition”;
the default video quality is “high definition”, how to set the default quality to “standard definition”?

Another qustion is that:can I take out the “low definition” and “high defintion” option? When the bindwith Change, the video quality only fluctuate within “low bandwidth” and “high definition”.