The rgba2nv12 function converts a 4-channel RGBA image to NV12
(4:2:0) format. The function outputs Y plane and interleaved UV plane
separately. NV12 holds the subsampled data, Y is sampled for every RGBA
pixel and U, V are sampled once for 2row and 2columns (2x2) pixels. UV
plane is of (rows/2)*(columns/2) size as U and V values are interleaved.
API Syntax
template <int SRC_T, int Y_T, int UV_T, int ROWS, int COLS, int NPC=1, int XFCVDEPTH_IN = _XFCVDEPTH_DEFAULT, int XFCVDEPTH_OUT_0 = _XFCVDEPTH_DEFAULT, int XFCVDEPTH_OUT_1 = _XFCVDEPTH_DEFAULT>
void rgba2nv12(xf::cv::Mat<SRC_T, ROWS, COLS, NPC, XFCVDEPTH_IN> & _src, xf::cv::Mat<Y_T, ROWS, COLS, NPC, XFCVDEPTH_OUT_0> & _y, xf::cv::Mat<UV_T, ROWS/2, COLS/2, NPC, XFCVDEPTH_OUT_1> & _uv)
Parameter Descriptions
The following table describes the template and the function parameters.
| Parameter | Description |
|---|---|
| SRC_T | Input pixel type. Only 8-bit,unsigned, 4-channel is supported (XF_8UC4). |
| Y_T | Output pixel type. Only 8-bit,unsigned, 1-channel is supported (XF_8UC1). |
| UV_T | Output pixel type. Only 8-bit,unsigned, 2-channel is supported (XF_8UC2). |
| ROWS | Maximum height of input and output image. |
| COLS | Maximum width of input and output image. Must be a multiple of 8 for 8 pixel mode. |
| NPC | Number of pixels to be processed per cycle; possible options are XF_NPPC1 and XF_NPPC8 for 1 pixel and 8 pixel operations respectively. |
| XFCVDEPTH_IN | Depth of input image |
| XFCVDEPTH_OUT_0 | Depth of output image |
| XFCVDEPTH_OUT_1 | Depth of output image |
| _src | Input RGBA image of size (ROWS, COLS). |
| _y | Output Y image of size (ROWS, COLS). |
| _uv | Output UV image of size (ROWS/2, COLS/2). |
Resource Utilization
The following table summarizes the resource utilization of RGBA to NV12 for different configurations, generated using Vivado HLS 2019.1 tool for the Xczu9eg-ffvb1156-1-i-es1 FPGA, to process a HD (1080x1920) image.
| Operating Mode | Operating Frequency (MHz) | Utilization Estimate | ||||
|---|---|---|---|---|---|---|
| BRAM_18K | DSP_48Es | FF | LUT | CLB | ||
| 1 Pixel | 300 | 0 | 9 | 802 | 452 | 128 |
Performance Estimate
The following table summarizes the performance of RGBA to NV12 for different configurations, as generated using Vivado HLS 2019.1 tool for the Xczu9eg-ffvb1156-1-i-es1, to process a grayscale HD (1080x1920) image.
| Operating Mode | Latency Estimate |
|---|---|
| Max Latency (ms) | |
| 1 pixel operation (300 MHz) | 1.8 |