ISP 24-bit Pipeline - 2024.1 English

Vitis Libraries

Release Date
2024-05-30
Version
2024.1 English
Imaging sensors that do not equip with a high bit-width on the transmission side can be compressed (compand) in a piece-wise linear (PWL) mapping to a lower bit depth.
Through the HDR De-companding kernel, the data can be recovered to higher bit-widths and processed through further kernels of ISP by converting to 14-bit for efficient use of resources.

This ISP 24-bit pipeline includes the following 17 blocks:

  • HDR Decompand
  • ConvertTo
  • RGBIR
  • Auto Exposure Correction(AEC)
  • Black level correction
  • Bad pixel correction
  • Degamma
  • Lens shading correction
  • Gain Control
  • Demosaicing
  • Tone Mapping
  • Auto white balance
  • ISP Stats
  • Colorcorrection matrix
  • Gamma correction
  • 3D LUT
  • Color space conversion

The current design example demonstrates how to use ISP functions in a pipeline.

../_images/block_diagram_24bit.png

The following table describes the parameters of the pipeline which can be configured dynamically.

Table 263 Table: Runtime Parameter for the Pipeline
Parameter Descriptions
height The number of rows in the image or height of the image.
width The number of columns in the image or width of the image.
rgain To configure gain value for the red channel.
bgain To configure gain value for the blue channel.
R_IR_C1_wgts 5x5 Weights to calculate R at IR location for constellation1
R_IR_C2_wgts 5x5 Weights to calculate R at IR location for constellation2
B_at_R_wgts 5x5 Weights to calculate B at R location
IR_at_R_wgts 3x3 Weights to calculate IR at R location
IR_at_B_wgts 3x3 Weights to calculate IR at B location
sub_wgts Weights to perform weighted subtraction of IR image from RGB image. sub_wgts[0] -> G Pixel, sub_wgts[1] -> R Pixel, sub_wgts[2] -> B Pixel sub_wgts[3] -> calculated B Pixel
bayerp Input Bayer pattern. XF_BAYER_BG, XF_BAYER_GB, XF_BAYER_GR, XF_BAYER_RG are the supported values.
params consists of slope and intercept values of four knee points in hdr decompand kernel for R, G, B.
params_14bit consists of slope and intercept values of four knee points to truncate 24bit to 14bit.
params_degamma consists of slope and intercept values of knee points till 64 to linearize the image.
paec %top and %bottom pixels are ignored while computing min and max to improve quality in AEC.
pawb %top and %bottom pixels are ignored while computing min and max to improve quality in AWB.
aec_stats Calculted histogram of the AEC input image.
awb_stats Calculted histogram of the AWB input image.
aec_max_bins List of maximum values per range of bins. This is only applicable if merge bins feature is enabled.
awb_max_bins List of maximum values per range of bins. This is only applicable if merge bins feature is enabled.
roi_tlx Top left x coordinate of ROI
roi_tly Top left y coordinate of ROI
roi_brx Bottom right x coordinate of ROI
roi_bry Bottom right y coordinate of ROI
zone_col_num Number of zones across column.
zone_row_num Number of zones across rows.
blk_height Actual block height
blk_width Actual block width
c1 To retain the details in bright area using, c1 in the tone mapping.
c2 Efficiency factor, ranges from 0.5 to 1 based on output device dynamic range.
gamma_lut Lookup table for gamma values.first 256 will be R, next 256 values are G gamma and last 256 values are B values
lutDim Dimension of input lut

The following table describes the template parameters which can be configured.

Table 264 Table: Compile Time Parameters
Parameter Description
XF_HEIGHT Maximum height of input and output image
XF_WIDTH Maximum width of input and output image (Must be multiple of NPC)
XF_INP_T Input pixel type,Supported pixel widths are 8,10,12,16
XF_BAYER_PATTERN The Bayer format of the RAW input image. Supported formats are BGGR, GRBG and GBRG.
BLACK_LEVEL black level value.
DEGAMMA_KP Number of knee points in degamma.
MAX_ZONES Maximum number of possible zones.
STATS_SIZE Number of bins per channel for the input image. This is equal to the number of output bins if merge bins feature is disabled.
FINAL_BINS_NUM Number of output bins per channel if merge bins feature is enabled.
MERGE_BINS To disable or enable merge bins feature.
SQLUTDIM Squared value of maximum dimension of input LUT
LUTDIM 33x33 dimension of input LUT

The following example demonstrates the ISP pipeline with the above list of functions.

    void ISPpipeline(ap_uint<INPUT_PTR_WIDTH>* img_inp,
                             ap_uint<OUTPUT_PTR_WIDTH>* img_out,
                             ap_uint<OUTPUT_PTR_WIDTH>* img_out_ir,
                             unsigned short height,
                             unsigned short width,
                             int params[3][4][3],
                             ap_ufixed<48, 24> params_14bit[3][4][3],
                             char R_IR_C1_wgts[25],
                             char R_IR_C2_wgts[25],
                             char B_at_R_wgts[25],
                             char IR_at_R_wgts[9],
                             char IR_at_B_wgts[9],
                             char sub_wgts[4],
                             unsigned short bayerp,
                             uint16_t rgain,
                             uint16_t bgain,
                             ap_ufixed<32, 16> params_degamma[3][DEGAMMA_KP][3],
                             uint32_t aec_hist0[HIST_SIZE_AEC],    /* function_aec */
                             uint32_t aec_hist1[HIST_SIZE_AEC],    /* function_aec */
                             uint32_t awb_hist0[3][HIST_SIZE_AWB], /* function_awb */
                             uint32_t awb_hist1[3][HIST_SIZE_AWB], /* function_awb */
                             int gain0[3],                         /* function_awb */
                             int gain1[3],                         /* function_awb */
                             uint16_t paec,
                             uint16_t pawb,
                             unsigned int* aec_stats,
                             unsigned int* awb_stats,
                             ap_uint<13>* aec_max_bins,
                             ap_uint<13>* awb_max_bins,
                             int roi_tlx,
                             int roi_tly,
                             int roi_brx,
                             int roi_bry,
                             int zone_col_num, // N
                             int zone_row_num, // M
                             unsigned char gamma_lut[256 * 3],
                             XF_CTUNAME(XF_SRC_T, XF_NPPC) omin_r[MinMaxVArrSize][MinMaxHArrSize], /* LTM */
                             XF_CTUNAME(XF_SRC_T, XF_NPPC) omax_r[MinMaxVArrSize][MinMaxHArrSize], /* LTM */
                             XF_CTUNAME(XF_SRC_T, XF_NPPC) omin_w[MinMaxVArrSize][MinMaxHArrSize], /* LTM */
                             XF_CTUNAME(XF_SRC_T, XF_NPPC) omax_w[MinMaxVArrSize][MinMaxHArrSize], /* LTM */
                             int blk_height,                                                       /* LTM */
                             int blk_width,                                                        /* LTM */
                             ap_ufixed<16, 4>& mean1,                                              /* gtm */
                             ap_ufixed<16, 4>& mean2,                                              /* gtm */
                             ap_ufixed<16, 4>& L_max1,                                             /* gtm */
                             ap_ufixed<16, 4>& L_max2,                                             /* gtm */
                             ap_ufixed<16, 4>& L_min1,                                             /* gtm */
                             ap_ufixed<16, 4>& L_min2,                                             /* gtm */
                             float c1,                                                             /* gtm */
                             float c2,                                                             /* gtm */
                             ap_uint<LUT_PTR_WIDTH>* lut,
                             int lutDim) {

                    #pragma HLS INLINE OFF

                    xf::cv::Mat<XF_INP_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_imgInput> imgInput1(height, width);
                    xf::cv::Mat<XF_HDR_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_hdr_out> hdr_out(height, width);
                    xf::cv::Mat<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_hdr_out> img_14bit(height, width);
                    xf::cv::Mat<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_rggb_out> rggb_out(height, width);
                    xf::cv::Mat<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_aecin> aec_in1(height, width);
                    xf::cv::Mat<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_aecin> aec_in2(height, width);
                    xf::cv::Mat<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_aec_out> aec_out(height, width);
                    xf::cv::Mat<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_bpc_out> bpc_out(height, width);
                    xf::cv::Mat<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_blc_out> blc_out(height, width);
                    xf::cv::Mat<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_dgamma_out> dgamma_out(height, width);
                    xf::cv::Mat<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_lsc_out> LscOut(height, width);
                    xf::cv::Mat<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_gain_out> gain_out(height, width);
                    xf::cv::Mat<XF_DST_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_demosaic_out> demosaic_out(height, width);
                    xf::cv::Mat<XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_ltm_out> ltm_out(height, width);
                    xf::cv::Mat<XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_awb_out> awb_out(height, width);
                    xf::cv::Mat<XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_awbin> awb_in1(height, width);
                    xf::cv::Mat<XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_awbin> awb_in2(height, width);
                    xf::cv::Mat<XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_dst> gamma_out(height, width);
                    xf::cv::Mat<XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_ccm> ccm_out(height, width);
                    xf::cv::Mat<XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_lut_out> lut_out(height, width);

            // clang-format off
            #pragma HLS DATAFLOW
                    // clang-format on

                    float awb_thresh = (float)pawb / 256;
                    float aec_thresh = (float)paec / 256;
                    float inputMax = (1 << (XF_DTPIXELDEPTH(XF_SRC_T, XF_NPPC))) - 1; // 65535.0f;

                    float mul_fact = (inputMax / (inputMax - BLACK_LEVEL));
unsigned int blc_config_1 = (int)(mul_fact * 65536); // mul_fact int Q16_16 format
unsigned int blc_config_2 = BLACK_LEVEL;
                    float inputmin = 0.0f;
                    float inputmax1 = 255.0f;
                    float outputmin = 0.0f;
                    float outputmax1 = 255.0f;
                    float inputmax2 = 16383.0f;
                    float outputmax2 = 16383.0f;
                    int outdepth = (1 << XF_DTPIXELDEPTH(XF_GTM_T, XF_NPPC));

                    xf::cv::Array2xfMat<INPUT_PTR_WIDTH, XF_INP_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_imgInput>(img_inp,
                                                                                                                                                                                                       imgInput1);

                    xf::cv::hdr_decompand<XF_INP_T, XF_HDR_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_imgInput, XF_CV_DEPTH_hdr_out>(
                            imgInput1, hdr_out, params, bayerp);

                    xf::cv::convert24To14bit<XF_HDR_T, XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_hdr_out,
                                                                     XF_CV_DEPTH_hdr_out>(hdr_out, img_14bit, params_14bit, bayerp);

                    function_rgbir_or_fifo<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_hdr_out, XF_CV_DEPTH_rggb_out,
                                                               XF_CV_DEPTH_rggb_out_ir, XF_CV_DEPTH_3XWIDTH>(img_14bit, rggb_out, img_out_ir, R_IR_C1_wgts,
                                                                                                                                                             R_IR_C2_wgts, B_at_R_wgts, IR_at_R_wgts,
                                                                                                                                                             IR_at_B_wgts, sub_wgts, height, width);

                    function_aec<XF_SRC_T, XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_aecin, XF_CV_DEPTH_aec_out>(
                            rggb_out, aec_out, height, width, aec_thresh, aec_hist0, aec_hist1);

                    xf::cv::blackLevelCorrection<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, 16, 15, 1, XF_CV_DEPTH_aec_out,
                                                                             XF_CV_DEPTH_blc_out>(aec_out, blc_out, blc_config_2, blc_config_1);
                    xf::cv::badpixelcorrection<XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, 0, 0, XF_CV_DEPTH_blc_out, XF_CV_DEPTH_bpc_out>(
                            blc_out, bpc_out);

                    function_degamma<XF_SRC_T, XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_bpc_out, XF_CV_DEPTH_dgamma_out,
                                                     DEGAMMA_KP>(bpc_out, dgamma_out, params_degamma, bayerp, height, width);
                    xf::cv::Lscdistancebased<XF_SRC_T, XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_dgamma_out,
                                                                     XF_CV_DEPTH_lsc_out>(dgamma_out, LscOut);

                    xf::cv::gaincontrol<XF_BAYER_PATTERN, XF_SRC_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_lsc_out,
                                                            XF_CV_DEPTH_gain_out>(LscOut, gain_out, rgain, bgain);

                    xf::cv::demosaicing<XF_BAYER_PATTERN, XF_SRC_T, XF_DST_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, 0, XF_CV_DEPTH_gain_out,
                                                            XF_CV_DEPTH_demosaic_out>(gain_out, demosaic_out);
                    if (XF_DST_T == XF_8UC3) {
                            fifo_copy<XF_DST_T, XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_demosaic_out, XF_CV_DEPTH_ltm_out>(
                                    demosaic_out, ltm_out, height, width);
                    } else {
                            function_tm<XF_DST_T, XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_demosaic_out, XF_CV_DEPTH_ltm_out>(
                                    demosaic_out, ltm_out, omin_r, omax_r, omin_w, omax_w, blk_height, blk_width, mean1, mean2, L_max1, L_max2,
                                    L_min1, L_min2, c1, c2, height, width);
                    }
                    xf::cv::duplicateMat<XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_ltm_out, XF_CV_DEPTH_awbin,
                                                             XF_CV_DEPTH_awbin>(ltm_out, awb_in1, awb_in2);

                    function_awb<XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_awbin, XF_CV_DEPTH_awb_out>(
                            awb_in1, awb_out, awb_hist0, awb_hist1, gain0, gain1, height, width, awb_thresh);
                    xf::cv::ispStats<MAX_ZONES, STATS_SIZE_AWB, FINAL_BINS_NUM, MERGE_BINS, XF_GTM_T, NUM_OUT_CH, XF_HEIGHT, XF_WIDTH,
                                                     XF_NPPC, XF_CV_DEPTH_awbin>(awb_in2, awb_stats, awb_max_bins, roi_tlx, roi_tly, roi_brx, roi_bry,
                                                                                                             zone_col_num, zone_row_num, inputmin, inputmax1, outputmin,
                                                                                                             outputmax1);
                    xf::cv::colorcorrectionmatrix<XF_CCM_TYPE, XF_GTM_T, XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_awb_out,
                                                                              XF_CV_DEPTH_ccm>(awb_out, ccm_out);
                    xf::cv::gammacorrection<XF_GTM_T, XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_ccm, XF_CV_DEPTH_dst>(
                            ccm_out, gamma_out, gamma_lut);

                    function_3dlut_fifo<XF_GTM_T, XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_dst, XF_CV_DEPTH_lut_out,
                                                            XF_CV_DEPTH_3dlut>(gamma_out, lut_out, lut, lutDim, height, width);
                    function_csc_or_mat_array<XF_GTM_T, XF_HEIGHT, XF_WIDTH, XF_NPPC, XF_CV_DEPTH_lut_out>(lut_out, img_out, height,
                                                                                                                                                                                               width);
    }

The ISP 24bit Pipeline design is validated on zcu102 board at 150 MHz frequency.

Table 265 Table: Resource Utilization Summary for a 1920x1080 Image
Operating Mode

Operating Frequency

(MHz)

Utilization Estimate
LUT FF BRAM_18k DSP URAM
1 Pixel 150 35734 38747 60 275 0
Table 266 Table: Performance Estimate Summary for a 1920x1080 Image
Operating Mode

Operating Frequency

(MHz)

Latency Estimate
Max (ms)
1 pixel 150 15.1ms