SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
The boxcar module generates a boxcar by taking mosaic image data and averaging the red, green, and blue pixels in an 8 × 8 or 16 × 16 block to produce one red, green, and blue output, as shown in Figure 9-88 and in Figure 9-89. Here, similar to the histogram module, the boxcar is enabled from the IPIPE_BOX_EN[0] EN bit, and if the mode is set to run once (one shot) (IPIPE_BOX_MODE[0] OST = 1), the enable bit is cleared after the run. The size of the blocks is determined from the IPIPE_BOX_SHF[0] SEL bit, where if set to 0 = 8 × 8, and 1 = 16 × 16.
The result of this operation is a full-color image with (1/64) or (1/256) area of the original image. The maximum input horizontal width is 8190 pixels when a 16 × 16 block is used; the width is 4096 when an 8 × 8 block is used. Also, the image size (width and height) must be a multiple of 16 for a 16 × 16 block, and a multiple of 8 for an 8 × 8 block. Boxcar operation works on 12-bit Bayer data and outputs 16-bit data. The output data is 48-bit RGB data for each 8 × 8 or 16 × 16 block. The 48-bit data is aligned in 64-bit format in SDRAM as shown in Figure 9-90. The first address of SDRAM access is specified by the IPIPE_BOX_SDR_SAD_H and IPIPE_BOX_SDR_SAD_L registers. The output data are written to SDRAM continuously line by line; there is no address offset between lines. After the image transfer of each frame completes, the ipipe_eof signal is sent to buffer logic. This signal is issued at the same timing as ipipe_int_dma.
The right-shift value is specified by the IPIPE_BOX_SHF register, which has a range of 0 to 4. (The shift down is performed to fit the 20-bit accumulated value into 16-bit output.) For green signal processing, a divide-by-two operation rounds off the LSB.