I am using Canon XH A1 ( note without lowercase 's' in the model number) since year and I have been noticing a lot of noisy grains which - I know - are results of low lighting conditions. Is there any technical method inside the camera by which noisy grains can be significantly reduced?

We need a bit more info to help you. What mode are you shooting in? What are your settings? One suggestion is to use the PFVISION preset. It was designed for low light shooting.

THe first and most important thing is to turn the AGC (auto gain control) switch to OFF. If it's on, the camera will pump up the gain to unacceptable levels in low light. You can then use the gain switch to add it as needed.

In low light, open the iris all the way, and then go to a slower shutter speed. You have also seen how you lose light as you zoom, so try and stay wide.

In the custom settings, you can work with the setup, pedestal, black stretch and noise reduction to help a bit, but remember that gain and iris are the key players here.

I am using Canon XH A1 ( note without lowercase 's' in the model number) since year and I have been noticing a lot of noisy grains which - I know - are results of low lighting conditions. Is there any technical method inside the camera by which noisy grains can be significantly reduced?

Try with NR1 setting to LOW and Coring to +5 and see how it goes. Offcouse make sure ND filters are off.

Cheers
Shelton.

In addition to what everybody has suggested above --- and you should follow all of those suggestions --- here are a couple more things to try.

1. I believe Oman use PAL, so you have the option of shooting 25p. If so, set your shooting mode to 25p, turn the control dial to the M setting, and turn the shutter speed down to 1/25. Try to keep the zoom at full wide. (Zooming in will cause the aperture size to decrease, thereby diminishing the amount of light collected.)

2. Check out the downloadable trial version of the Neat Video de-noiser on some of your footage and see if that helps.