Biquad filtering experts required

Hi! Are you familiar with transposed IIR algorithms? I have been working on a double precision biquad cascade algorithm (direct form 2 tranposed) and need some help. The algorithm reads audio samples (stereo) from an array and calculates states before moving onto the the next sample. The functions allows you to set up a biquad cascade of biquads. Code is fairly well documented. Can you debug and or make any suggestions to improve? Target platform is TI C674x DSP but any will do really to prove that it works correctly.