Bandwidth

[tylerr]

Is there a formula to calculate bandwidth needed per channel or per universe?

[tbaarsch]

Hi Tylerr,

DMX runs at 250kbits/sec.

If it is Art-Net Bandwidth that you are after, the basic formula is:

Bandwidth = (Number of Universes) (DMX Refresh Rate - 40) (Art-Net Packet Size - 523)

In practice you will need to factor this formula by 10 in order to account for network traffic etc.

If you need to know more, I recommend the book Rock Solid Ethernet by Wayne Howell.

Tim

[bswinnen]

1 ArtDmx packet is 572 bytes long, every byte is 8 bit long.
So at a refresh rate of 40 FPS the used bandwidth per universe in my opinion is:

b = 40 * 572 * 8 / 1000000
b = 0.18304 Mbit/s

At 40 FPS:
Theoretical margin on 10Mbit/s = 10/0.18204 = 54.63 (54 universe)
Theoretical margin on 100Mbit/s = 100/0.18204 = 546.3 (546 universe)

Max number of ArtNet universes from 1 source is 256. So at 40 FPS it takes 46.85 Mbit/s

Take in mind that you need margin for other network protocols as this is in theory. In practice count in some overhead. but it gives you a good idea.

I must say that I have to check if a byte takes only 8 bit on a network bandwidth or if I need to count in start and stop bits in here. However the idea is clear I think.

[tbaarsch]

Hi,

An Art-Net packet always contains 512 channels so the bandwidth to send one channel is the same as required for sending all 512.

Tim