Photon Focus DR1-D3360-192-G2-8, User Manual, Page: 75 / 119

Figure 5.44: LFSR test pattern received and histogram containing transmission errors
5.12 Double Rate (DR1 cameras only)
The Photonfocus DR1 cameras use a proprietary coding algorithm to cut the data rate by
almost a factor of two. This enables the transmission of high frame rates over just one Gigabit
Ethernet connection, avoiding the complexity and stability issues of Ethernet link aggregation.
The algorithm is lossy but no image artefacts are introduced, unlike for example the JPEG
compression. It is therefore very well suited for most machine vision applications except for
measuring tasks where sub-pixel precision is required.
Double rate modulation can be turned off for debugging purposes.
The encoded image is transmitted in mono 8 bit data resolution.
The encoding is run in real-time in the camera’s FPGA. A DLL for the demodulation of the
image for SDK applications is included in the PFInstaller software package that can be
downloaded from Photonfocus (see also 7).
The compression factor is independent of the image content. The encoded image has the same
number of rows as the raw image. The required image width (number of bytes in a row) for
the modulated image can be calculated as follows (value can also be read from a camera
property) (oh=2 for monochrome cameras, oh=3 for color cameras):
w
mod
= ceil(w/64) + w/2 + oh
5.12 Double Rate (DR1 cameras only) 75