SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
The FV calculator takes the unsigned red/green/blue extracted data and subtracts 128 or 512 (depending on whether A-Law is enabled) to place the data in the range –128 to 127 or –512 to 511.
After removing the offset, the data is sent through two parallel IIR filters configured in a dual-biquad configuration. Each filter uses a unique set of 11 programmable coefficients. Each coefficient is 12-bits-wide with 6 bits of decimal, S12Q6 (VISS_RAWFE_H3A_AFCOEF010 to VISS_RAWFE_H3A_AFCOEF0010 for SET0, and VISS_RAWFE_H3A_AFCOEF110 to VISS_RAWFE_H3A_AFCOEF1010 for SET1). The filter-shift registers are cleared on each horizontal line at the position set by the register IIR horizontal start register (the VISS_RAWFE_H3A_AFIIRSH[11:0] IIRSH bit field). The absolute values of the output (16 bits wide with 4 bits of decimal, U16Q4) of both filters are then sent to the AF accumulator module. Signed clipping is performed during the FV calculation. If the input value is m bits (signed) and the required output value is n bits, clipping transforms the input to between –21 and 21. Values lower than –21 are set to –21, and values higher than 21 are set to 21.