【正文】 w 123 157 142 127 131 102 99 235134 135 157 112 109 106 108 136135 144 159 108 112 118 109 126176 183 161 111 186 130 132 133137 149 154 126 185 146 131 132121 130 127 146 205 150 130 126117 151 160 181 250 161 134 125168 170 171 178 183 179 112 124136 170 155 140 144 115 112 248 12 14145 146 168 123 120 117 119 147 12 10144 153 168 117 121 127 118 135 9 9176 183 161 111 186 130 132 133 0 0144 156 161 133 192 153 138 139 7 7122 131 128 147 206 151 131 127 2 0121 155 164 185 254 165 138 129 4 4173 175 176 183 188 184 117 129 5 5Covered cells Before zerobias adjustment After zerobias adjustment 1311907145Zerobias adjustment 7 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis Compression ? Store more images ? Transmit image to PC in less time ? JPEG (Joint Photographic Experts Group) – Popular standard format for representing digital images in a pressed form – Provides for a number of different modes of operation – Mode used in this chapter provides high pression ratios using DCT (discrete cosine transform) – Image data divided into blocks of 8 x 8 pixels – 3 steps performed on each block ? DCT ? Quantization ? Huffman encoding 8 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis DCT step ? Transforms original 8 x 8 block into a cosinefrequency domain – Upperleft corner values represent more of the essence of the image – Lowerright corner values represent finer details ? Can reduce precision of these values and retain reasonable image quality ? FDCT (Forward DCT) formula – C(h) = if (h == 0) then 1/sqrt(2) else ? Auxiliary function used in main function F(u,v) – F(u,v) = 188。 if( ++rowIndex == SZ_ROW ) { colIndex = 1。 static char buffer[SZ_ROW][SZ_COL]。 colIndex = 1。 rowIndexSZ_ROW。 } } } rowIndex = 0。 void CcdppInitialize() { rowIndex = 1。 for(rowIndex=0。 colIndex++) { buffer[rowIndex][colIndex] = CcdPopPixel()。 colIndex++) { buffer[rowIndex][colIndex] = bias。 pixel = buffer[rowIndex][colIndex]。 } } return pixel。 } 22 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis CODEC module ? Models FDCT encoding ? ibuffer holds original 8 x 8 block ? obuffer holds encoded 8 x 8 block ? CodecPushPixel called 64 times to fill ibuffer with original block ? CodecDoFdct called once to transform 8 x 8 block – Explained in next slide ? CodecPopPixel called 64 times to retrieve encoded block from obuffer static short ibuffer[8][8], obuffer[8][8], idx。 x8。 } idx = 0。 } short CodecPopPixel(void) { short p。 return p。 int x。 } for(x=0。 } static short ONE_OVER_SQRT_TWO = 23170。 iSZ_ROW。 UartSend(((char*)temp)[0])。 for(i=0。 j++) buffer[i][j] = CcdppPopPixel()。 jNUM_COL_BLOCKS。 l8。 k8。 /* part 2 quantization */ buffer[i*8+k][j*8+l] = 6。 CcdInitialize(imageFileName)。 /* simulate functionality */ CntrlCaptureImage()。 static unsigned char xdata U_STAT_REG _at_ 65534。 } void UartSend(char d) { fprintf(outputFileHandle, %i\n, (int)d)。 } Rewritten UART module include static FILE *outputFileHandle。 CntrlSendImage()。 CodecInitialize()。 char *imageFileName = argc 2 ? argv[2] : 。 l8。 CodecDoFdct()。 k8。 iNUM_ROW_BLOCKS。 i++) for(j=0。 /* send lower byte */ } } } define SZ_ROW 64 define SZ_COL 64 define NUM_ROW_BLOCKS (SZ_ROW / 8) define NUM_COL_BLOCKS (SZ_COL / 8) static short buffer[SZ_ROW][SZ_COL], i, j, k, l, temp。 jSZ_COL。 } static double C(int h) { return h ? : ONE_OVER_SQRT_TWO / 。 x++) r += s[x] * COS(x, u)。 x8。 x C(u) x C(v) Σx=0..7 Σy=0..7 Dxy x cos(π(2u + 1)u/16) x cos(π(2y + 1)v/16) ? Only 64 possible inputs to COS, so table can be used to save performance time – Floatingpoint values multiplied by 32,678 and rounded to nearest integer – 32,678 chosen in order to store each value in 2 bytes of memory – Fixedpoint representation explained more later ? FDCT unrolls inner loop of summation, implements outer summation as two consecutive for loops static const short COS_TABLE[8][8] = { { 32768, 32138, 30273, 27245, 23170, 18204, 12539, 6392 }, { 32768, 27245, 12539, 6392, 23170, 32138, 30273, 18204 }, { 32768, 18204, 12539, 32138, 23170, 6392, 30273, 27245 }, { 32768, 6392, 30273, 18204, 23170, 27245, 12539, 32138 }, { 32768, 6392, 30273, 18204, 23170, 27245, 12539, 32138 }, { 32768, 18204, 12539, 32138, 23170, 6392, 30273, 27245 }, { 32768, 27245, 12539, 6392, 23170, 32138, 30273, 18204 }, { 32768, 32138, 30273, 27245, 23170, 18204, 12539, 6392 } }。 p = obuffer[idx / 8][idx % 8]。 ibuffer[idx / 8][idx % 8] = p。 y8。 } void CodecDoFdct(void) { int x, y。 void UartInitialize(const char *outputFileName) { outputFileHandle = fopen(outputFileName, w)。 if( ++rowIndex == SZ_ROW ) { colIndex = 1。 colIndex = 0。 for(colIndex=0。 rowIndex++) { for(colIndex=0。 } void CcdppCapture(void) { char bias。 } 20 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis CCDPP (CCD PreProcessing) module ? Performs zerobias adjustment ? CcdppCapture uses CcdCapture and CcdPopPixel to obtain image ? Performs zerobias adjustment after each row read in define SZ_ROW 64 define SZ_COL 64 static char buffer[SZ_ROW][SZ_COL]。 colIndexSZ_COL。