Reply To: Getting CRT-like brightness from original Xbox to LCD monitor

[Zacabeb]

On the Xbox, both 720×480 and square pixel 640×480 are in fact supported rendering resolutions, but how they’re handled for output differ between encoders as mentioned in another thread. 🙂

Square pixel 480p (780 samples per line) of course differs from VGA (800 samples per line,) making them incompatible for proper aspect ratio and centering. But there’s nothing stopping the use of any pixel clock in analog video so long as the signal is within bandwidth, permitting NTSC square pixel and BT.601 to coexist.

There is a dilemma when it comes to ITU-R BT.601 and derived 480p and 576p standards. The pixel aspect ratios aren’t always adhered to in accordance with legacy. When converting HDTV to SDTV or EDTV, scaling down to cover the full 720 pixel raster including margins instead of the correct 711, 704, or 702 pixels was not only technically easier, but helpful as it extended picture into the blanking area for masking to suppress ringing from the leading edge of active video. The vertical scaling was not modified to keep the proper pixel aspect ratio, leading to new pixel aspect ratios. The same can happen in upscaling to HDTV. The assumption was that the discrepancy would be small enough go unnoticed by most viewers.

The standards have actually become quite a mess. 😄