HD bandwidth

HD-SDI (SMTPE 292M) bandwidth

1080i

Interlaced 1080i video at 30Hz (60i) has the following dimensions:

• active samples x lines: 1920x1080
• total samples x lines: 2200x1125

The HD-SDI data transmission is designed for 10-bit video sampled at 4:2:2, and thus the following calculation hols: 2200*1125*30[b/img]*30[fps]*2/3[4:2:2 sampling] = 1485000000 which is exactly the 1.485 Gbps thing that HD standard says. If we transmit the active HD data stripped off of inactive samples, the formula would be: 1920*1080*30[b/img]*30[fps]*2/3[4:2:2 sampling] = 1244160000 and thus the bandwidth would be 1.244 Gbps.

Of course, there are other formats like 1080i at 30Hz/1.001 (denoted also as 30/M), which is equivalent to NTSC 29.97 Hz image and 1080i at 25Hz, which differs from the previous two by the number of total samples per line (2640, so that total samples/lines is 2640x1125).

1080p, 1080sF

There are equivalent progressive 1080p modes resulting in the same data rates when framerate is <=30Hz. If 50Hz, 59.94Hz and 60Hz is used, the bandwidth is doubled and thus dual-link SDI (SMPTE 372M) is needed.

Furthermore, there are so called segmented progressive modes denoted as 1080sF. They also work with separate odd and even lines, but the difference to the interlaced video is that both even and odd lines come from the same progressive image. This mode has been developed in order to be able to work with progressive video using intelacing equipment. The bandwidth is equivalent to the respective 25 - 30Hz 1080p modes.

Related Information

• Very useful for understanding different HD formats is a XILINX Application Note 680.
• Different HD and above resolutions