A more in-depth description can be found on here: http://www.playtool.com/pages/dvicompat/dvi.htmlThe blanking is in the DVI signal, which has gaps between each scanline and each frame, just like an analog signal, during which it sends nothing but null bytes. 1920x1200 is pushing the limits of single-link DVI's bandwidth using normal (CRT-style) blanking, but if you use shorter blanking periods, there's less data to send, so you can use a lower data rate.
Ah, thanks, I knew about traditional blanking time in composite video systems (and VGA), didn't know that it was also used in HDMI, and therefore could be reduced.Mortimer wrote:A CRT screen requires blanking time to allow time for the scanning beam to move from one side of the screen to the other to start drawing the next line, and to go from bottom to top to start the next screen, plus overscan and black borders. All this time when the beam is not drawing anything on the screen is "blanking time". An LCD monitor using DVI-D doesn't need blanking time, but it is included in the pixel stream anyway. This time can be reduced, which in turn means that for a given resolution at a particular frequency, the pixel clock frequency can be reduced. This reduces the power requirement on the sending end, in this case the RPi which could be useful, reduces error rates, and will likely increase the length of cable possible between the computer and the monitor.