I am trying to migrate portions of a ZYNQ design from one platform to another. Part of the project is based on Avnet's ALI3 touchscreen kit. From the docs:
The 7-inch Zed Touch Display Kit includes a WVGA (800x480) LCD panel. To better understand the memory storage and bandwidth involved with this video resolution, let’s perform some calculations:
- Active area = 800 x 480
- Frame rate = 60 Hz
- Pixel rate = 33.333333 MHz
- Pixel format = 24 bits RGB
Video Storage Requirements:
- (800 x 480) pixels x 24 bits/pixel = 9.2 Mbits
Video Bandwidth Requirements:
- (800 x 480) pixels x 24 bits/pixel x 60 frames/sec = 533 Mbits/sec
The LCD panel has a serial LVDS interface. This means that the 24 bit parallel video interface must be serialized by a factor of 7:1, before being transmitted on four LVDS differential pairs. A fifth LVDS differential pair is used to transmit the clock.
Notwithstanding the significant rounding down of the Video Bandwidth Requirements result, it is not obvious to me why the video "must" be serialized by the specific factor of 7:1.
Is this an industry standard video thing, or does 7:1 follow from the numbers given? What am I missing?