1080p Math
Posted November 18th, 2006 @ 03:34pm by Erik J. Barzeski
Let's perform a thought experiment wherein we take a pure, uncompressed 1080p signal. How much bandwidth would it take to display the signal at 60 FPS?
1920 * 1080 = 2073600 number of pixels 2073600 * 24 = 49766400 24-bit color (16.7M colors) 49766400 * 60 = 2985984000 60 frames per second 2985984000 / 8 = 373248000 convert to bytes/sec 373248000 / 1024 = 364500 convert to KB/sec 364500 / 1024 = 355.957 convert to MB/sec
So there you have it: uncompressed 1080p at 60 FPS and 24-bit color would take more than 350 MB/sec bandwidth. HDMI supports 48-bit color, so double the numbers and you're well above half a gigabyte per second of data.
Math like this really impresses upon us all how well modern codecs truly work. For example, a 1920 x 1080 "BBC HD" video I downloaded from Apple clocks in at 24 FPS, 1:33.5, and only 93.10 MB. Scaling 356 MB/sec by a 24:60 factor gives roughly 142 MB/sec. This particular video plays at barely more than 1 MB/sec (8.38 mb/sec), a savings of nearly 99.3%.
Donate Life
Posted 19 Nov 2006 at 11:20am #
I believe only the 'i' specs go up to 60fps. 1080p only goes up to 30fps. Recalc in order.
Reference here.
Posted 19 Nov 2006 at 6:23pm #
[quote comment="24031"]I believe only the 'i' specs go up to 60fps. 1080p only goes up to 30fps. Recalc in order.
Reference here.[/quote]
From that same source:
No new math needed. Simply changing to 48-bit color from 24-bit and moving from 60 FPS to 30 keeps the results the same. Otherwise, divide or multiply by two.
Posted 10 Nov 2007 at 2:05pm #
An even simpler way of "doing the math":
*1080p Uncompressed Video Bandwidth*
1920x1080 resolution = 2,073,600 pixels
2,073,600 pixels @ 24bpp = 49,766,400 bits (49Mbits)
49,766,400 bits / 8Mbits (8Mbits per Megabyte) = 6,220,800 bytes (6.2Mbytes)
So, 6.2Mbytes per frame.
6,220,800 bytes x 30 fps = 186,624,000 bytes/sec (187Mbytes/sec)
6,220,800 bytes x 60 fps = 373,248,000 bytes/sec (373Mbytes/sec)