• Dear VA-Community,

With this first post I would like to share a usefull approach on how to make VA related caluclations.

The calulations itself are linked to the google calculator making the usage pretty simple...

I think nearly everybody implementing or sketiching a VA design needs to take care of the over-all bandwidth concerning a CL/GigE/CXP/CLHS camera delivering or a PCIe DMA transfering data.

For example related to camera interface, some general ideas:

Bandwidth from CL camera

CL camera is configured for CL FULL 8 bit with 8 taps and a pixel clock of 85 MHz:

• bit depth = B = 8
• tap count = T = 8
• pixel clock = PXC = 85 MHz
• bandwidth = B * T * PXC

B * T * PXC = 8 bit * 8 * 85 MHz = (8 bit) * 8 * (85 MHz) = 680 MB / s , linked to google calculator to place your own values.

Please be aware that this bandwidth is a theoretical value.

While this is a camera / sensor related question, an estimation would be fine,

Theoretical maximum frame rate on basis of bandwidth:

• width = W = line length in pixels = 1920
• height = H = amount of lines = 1080
• bit depth = B = 8 bit
• size = W * H * B = amount of data per image
• framerate = bandwidth / size = bandwidth / (W * H * B)
where bandwidth is B * T * PXC, see idea above

frame rate = bandwidth / size = (B * T * PXC) / (W * H * B) =
(8 bit * 8 * 85 MHz) / (1920 * 1080 * 8 bit) = ((8 bit) * 8 * (85 MHz)) / (1920 * 1080 * (8 bit)) = 327.9 Hz, linked to google calculator to place your own values.

Bandwidth requirement on basis of frame dimension/size and frame rate:

More VA related:

Required parallelism on basis of bandwidth:

• system clock = C = VA platform frequency = 125 MHz
default mE5 = 125 MHz or mE4 = 62.5 MHz
• parallelism = P = bandwidth / C = F * (W * H ) / C, where P is always integer
((1920 * 1080) * 210 Hz) / (125 MHz) = 3.48, where 4 is the value to use.

If you wonder where the bit-depth has gone: it is a link property that is independent of parallelism.

Required DMA performance for de-mosaicking a bayer-pattern and transferring color/RGB data to host system:

bandwidth input = size * frame rate = F * S = F * (W * H * B) = 210 Hz * (1920 * 1080 * (8 bit)) = 435.5 MB / s

DMA bandwidth output = (1920 * 1080) * (210 Hz) * (24 bit) = 1.3 GB / s

where DMA paralleism is still ((1920 * 1080) * 210 Hz) / (125 MHz) = 3.48 = 4

From time to time I will put some more calculations here.

It would be handy to have these inside VA, but as long as missing: Google is a good friend.

Best regards,

Björn Rudde
Field Application Engineer / Consultant - Basler AG

• Of course there are more online calculators...

and Yes, Wolfram-Alpha is a good friend, too

delivering the same results in a more detailed fashion...

Example:

frame rate = bandwidth / size = (B * T * PXC) / (W * H * B) =

(8 bit * 8 * 85 MHz) / (1920 * 1080 * 8 bit) =
((8 bit) * 8 * (85 MHz)) / (1920 * 1080 * (8 bit)) = 327.9 Hz,

Fun fact: In case you earn a single \$ per frame you process, what would you get per year:

((8 bit) * 8 * (85 MHz)) / (1920 * 1080 * (8 bit)) * 1 \$ in € / year

Best regards,

Björn Rudde
Field Application Engineer / Consultant - Basler AG

• Dear Community,

A detailed approach into bandwidth considerations including additional calculations can be found here:

VQ8-CXP6D-DepthFromFocus

The linked thread is mainly related to bandwdith details of a CXP system.

In case you are using a CXP camera the folowing formulas may be of interest.

That means up to 12.5 or 6.25 Gbit/s per link depending on the used grabber.

Due to 8b/10b encoding this represents per link at CXP6:

(8 / 10) * (6.25 (Gbit / s)) = 625 MB / s

((4 * 8) / 10) * (6.25 (Gbit / s)) = 2500 MB / s

Since the interface is protocol based you will not get the full bandwidth for image data.

But at least it is the possible peak performance for CXP link itself.

The possible camera sensor data output will always be below these limits.

There are more options being supported by the VA design, but depending on the used platform:

 CXP-1 1.25 Gbit/s up to 212 m CXP-2 2.5 Gbit/s up to 185 m CXP-3 3.125 Gbit/s up to 169 m CXP-5 5 Gbit/s up to 102 m CXP-6 6.25 Gbit/s up to 60 m CXP-10 10 Gbit/s up to 40 m CXP-12 12.5 Gbit/s up to 30 m

Source of table: Wikipedia

Max link speed for mE5-MA-VCX-QP and mE5-VQ8-CXP6D is CXP6.

Status: 2nd of July 2020, current overview

Some math again for CXP1 speed with 4 links:

((4 * 8) / 10) * (1.25 (Gbit / s)) = 500 MB / s, where this peak bandwidth is very likely transporting 400 MB/s of image data.

Similar for CXP5 configuration with one link:

((1 * 8) / 10) * (5 (Gbit / s)) = 500 MB / s

Always check the CXP configuration using the hardware dialog in GenICam Explorer or microDisplayX.

The link topology will tell you what you are using precisely for CXP.

This will link to the documentation of link topology dialog, but screenshots are for GEV, but same steps for CXP.

Best regards

Björn Rudde
Field Application Engineer / Consultant - Basler AG

• Hello together,

Does anyone require some more examples of VA related calculations?