Nvidia GeForce GTX 580
Broken: 2.79 5bd8ac9cbfa
Worked: 2.78 3c043732d3f
Short description of error
After the remake of the Encoding settings in Render tab the Rate: settings is greyed out and non editable.
If a blend is saved in 2.78, with custom bitrate set, that file is opened as normal editable in 2.79, but any additional scenes created there have greyed out rate settings.
(Tested with 2.79 and 2.79a, default settings and startup scene)