Not able to update firefox prefrenecs in geckodriver

Question

I am launching firefox version 51 using geckodriver with following code to setpreferences but when i see in action:config in firefox . Preferences are not getting updated

nodeAddress = 20.20.20.20 #Node addres where browser is getting launched
d = DesiredCapabilities.FIREFOX
d['loggingPrefs'] = {'browser': 'ALL'}
d['marionette'] = True
d['binary'] = 'C:\\Program Files (x86)\\Mozilla Firefox\\firefox.exe'
f = webdriver.FirefoxProfile()
f.set_preference('media.navigator.permission.disabled', True)
d['firefox_profile']=f.encoded
driver = webdriver.Remote(command_executor=nodeAddress,desired_capabilities=f)

Also tried this too

nodeAddress = 20.20.20.20 #Node addres where browser is getting launched
d = DesiredCapabilities.FIREFOX
d['loggingPrefs'] = {'browser': 'ALL'}
d['marionette'] = True
d['binary'] = 'C:\\Program Files (x86)\\Mozilla Firefox\\firefox.exe'
f = webdriver.FirefoxProfile()
f.set_preference('media.navigator.permission.disabled', True)
driver = webdriver.Remote(command_executor=nodeAddress,desired_capabilities=f,browser_profile=f.encoded)