Lightning Bandwidth consideration and calculation

Lightning Bandwidth consideration and calculation

In order to provide maximum image quality, near zero latency, lightning requires the use of 10Gb network infrastructure. Below is a guide on calculating actual bandwidth of video signals, for resolutions with bandwidth requirements above 10Gb, light compression is applied to bring it under the 10Gb limit

To calculate approximate maximum network bandwidth for a given video resolution, the following formulas can be used:
LineFq (KHz) = Ver_res_total x fps
Network BW (Gbps) = Hor_res x Ebpp x LineFq x 1.05 / 1000000
• LineFq: Video line Frequency in Khz
• Ver_res_total: Total number of lines including vertical blanking
• Hor_Res: Horizontal pixel resolutions
• Ebpp: Effective bits per pixel. For example RGB 8 bit has 24 effective bits per pixel. Meanwhile YUV 420 8 bit has 12 effective bits per pixel while YUV 422 8 bit has 16 effective bits per pixel. Similarly, RGB or YUV 444 10 bit has 30 effective bits per pixel while YUV 420 10 bits has 15 effective bits/pixel while YUV 422 has 20 effective bits/pixel.
• 1.05: Scaling factor to take into account approximate network overhead based on packet overhead, packet payload size, packet preamble and minimum inter packet gap.
• 1,000,000: Scaling factor to bring network Bandwidth to Gbps unit

Here are two examples to calculate network bandwidth for two different resolutions:
Resolution 1920×1080 60Hz RGB 8 bit
LineFq = 1120 lines * 60 Hz / 1000 = 67.5
NetBW = 1920 * 24 * 67.5 * 1.05 = 3.27 Gbps
Resolution 3840×2160 30Hz YUV 8 bit
LineFq = 2250 lines * 30 Hz / 1000 = 67.5
NetBW = 3840 * 24 * 67.5 * 1.05 = 6.53 Gbps

The table below shows approximate maximum network bandwidth for a few select resolutions. To calculate approximate maximum network bandwidth for other resolutions, use the formulas above.

RESOLUTION Hvisible Htotal Vvisable Vtotal colour format format colour depth Ebpp Line (KHz) Frame (Hz) BW line Network Bandwidth
720P 1280 1648 720 750 RGB 888 24 24 45 60 1.382 1.451
                         
1080i 1920 2200 1080 1125 RGB 888 24 24 33.75 30 1.555 1.632
                         
1080P 1920 2200 1080 1125 RGB 888 24 24 67.5 60 3.11 3.265
  1920 2200 1080 1125 YUV 422 24 16 67.5 60 2.073 2.177
  1920 2200 1080 1125 YUV 420 24 12 67.5 60 1.555 1.632
                         
UHD 24 3840 5500 2160 2250 RGB 888 24 24 67.5 24 4.976 5.225
                         
UHD 30 3840 5500 2160 2250 RGB 888 24 24 67.5 30 6.22 6.531
  3840 5500 2160 2250 YUV 422 24 16 67.5 30 4.147 4.354
  3840 5500 2160 2250 YUV 420 24 12 67.5 30 3.11 3.265
                         
UHD 60 3840 5500 2160 2250 RGB 888 24 24 135 60 12.441 13.063
  3840 5500 2160 2250 YUV 422 24 16 135 60 8.294 8.709
  3840 5500 2160 2250 YUV 420 24 12 135 60 6.22 6.531
  3840 5500 2160 2250 YUV 422 30 20 135 60 10.368 10.886
  3840 5500 2160 2250 YUV 420 30 15 135 60 7.776 8.165

Approximate maximum network bandwidth for several common video resolutions