How should line_length be calculated?

I haven’t seen any concrete method of calculating this value. The JetPack docs state:

Specifies the pixel line width horizontal timing size for the sensor mode for calibrating the features in the camera stack.
This value must be equal or larger than active_w.

Is there anything a bit more specific? Does it really matter?

hello acsmith,

line_length is used to calculate the exposure time and frame rate settings.
in generally, we would set the line_length property as same as sensor register’s value.
you should also contact your sensor vendor to understand the correct settings.

moreover, all these properties in device tree indeed matters.
there are descriptions of the device tree properties, please access the [Sensor Driver Programming Guide] from the [Release 28.2 developer guide]
thanks

Hello,

I just searched the l4t 28.2.1 kernel-4.4 sources to try to understand how “line_length” is used, hoping to better understand which value I should put there, but actually it is not used by the kernel !!! Did I miss something ?

hello phdm,

line_length is used to calculate the exposure time and frame rate settings.
you’re correct that kernel side did not use the line_length for calculation, please aware that there are two path for v4l2src and nvcamerasrc.
you may check the Camera Architecture Stack via [NVIDIA Tegra Linux Driver Package]-> [Development Guide]-> [Camera Development]