Diff: aanIDCT.cpp

Revision:

3:a7547692071d

Child:

6:d7ee458cacd1

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/aanIDCT.cpp	Mon Nov 05 22:47:05 2012 +0000
@@ -0,0 +1,162 @@
+// aanIDCT.cpp
+// based: http://www.ijg.org/ libjpeg(jpeg-8d)jidctfst.c jidctflt.c jidctmgr.c
+#include "mbed.h"
+#include "aanIDCT.h"
+
+#define DCTSIZE 8
+#define DCTSIZE2 64
+#define CONST_BITS 8
+#define PASS1_BITS 2
+#define SCALE_BITS 14
+#define LOG2_CONST 3
+#define FIX_1_082392200 277
+#define FIX_1_414213562 362
+#define FIX_1_847759065 473
+#define FIX_2_613125930 668
+const uint16_t aanscales[] = {
+16384, 22725, 21406, 19265, 16384, 12872,  8866,  4520,
+22725, 31520, 29691, 26722, 22725, 17855, 12298,  6269,
+21406, 29691, 27969, 25171, 21406, 16819, 11585,  5906,
+19265, 26722, 25171, 22653, 19265, 15136, 10426,  5315,
+16384, 22725, 21406, 19265, 16384, 12872,  8866,  4520,
+12872, 17855, 16819, 15136, 12872, 10114,  6966,  3551,
+ 8866, 12298, 11585, 10426,  8866,  6966,  4798,  2446,
+ 4520,  6269,  5906,  5315,  4520,  3551,  2446,  1247,
+};
+
+#if 0
+inline int DESCALE(int x, int n) {
+    return (x / (1<<(n)));
+}
+#else
+#define DESCALE(x, n) ((x)/(1<<(n)))
+#endif
+
+int DEQUANTIZE(int coef, int quantval) {
+    return DESCALE(coef * quantval, SCALE_BITS-PASS1_BITS);
+}
+
+#if 1
+int MULTIPLY(int a, int b) {
+    return DESCALE(a * b, CONST_BITS);
+}
+#else
+#define MULTIPLY(a, b) (((a)*(b))/(1<<CONST_BITS))
+#endif
+
+int IDESCALE(int x) {
+    return DESCALE(x, PASS1_BITS+LOG2_CONST);
+}
+
+void aanIDCT::conv(int8_t output[], int16_t input[])
+{
+    uint16_t* quant = (uint16_t*)aanscales;
+    for(int pos = 0; pos < DCTSIZE; pos++) {
+        if (input[pos+DCTSIZE*1] == 0 && input[pos+DCTSIZE*2] == 0 &&
+               input[pos+DCTSIZE*3] == 0 && input[pos+DCTSIZE*4] == 0 &&
+               input[pos+DCTSIZE*5] == 0 && input[pos+DCTSIZE*6] == 0 &&
+               input[pos+DCTSIZE*7] == 0) {
+            int dcval = DEQUANTIZE(input[pos+DCTSIZE*0], quant[pos+DCTSIZE*0]);
+            for(int y = 0; y < DCTSIZE; y++) {
+                ws[pos+DCTSIZE*y] = dcval;
+            }
+            continue;
+        }
+        // Even part
+        int tmp0 = DEQUANTIZE(input[pos+DCTSIZE*0], quant[pos+DCTSIZE*0]);
+        int tmp1 = DEQUANTIZE(input[pos+DCTSIZE*2], quant[pos+DCTSIZE*2]);
+        int tmp2 = DEQUANTIZE(input[pos+DCTSIZE*4], quant[pos+DCTSIZE*4]);
+        int tmp3 = DEQUANTIZE(input[pos+DCTSIZE*6], quant[pos+DCTSIZE*6]);
+
+        int tmp10 = tmp0 + tmp2;    // phase 3
+        int tmp11 = tmp0 - tmp2;
+
+        int tmp13 = tmp1 + tmp3;    // phases 5-3
+        int tmp12 = MULTIPLY(tmp1 - tmp3, FIX_1_414213562) - tmp13; // 2*c4
+
+        tmp0 = tmp10 + tmp13;   // phase 2
+        tmp3 = tmp10 - tmp13;
+        tmp1 = tmp11 + tmp12;
+        tmp2 = tmp11 - tmp12;
+
+        // Odd part
+        int tmp4 = DEQUANTIZE(input[pos+DCTSIZE*1], quant[pos+DCTSIZE*1]);
+        int tmp5 = DEQUANTIZE(input[pos+DCTSIZE*3], quant[pos+DCTSIZE*3]);
+        int tmp6 = DEQUANTIZE(input[pos+DCTSIZE*5], quant[pos+DCTSIZE*5]);
+        int tmp7 = DEQUANTIZE(input[pos+DCTSIZE*7], quant[pos+DCTSIZE*7]);
+
+        int z13 = tmp6 + tmp5;  // phase 6
+        int z10 = tmp6 - tmp5;  
+        int z11 = tmp4 + tmp7;
+        int z12 = tmp4 - tmp7;
+
+        tmp7 = z11 + z13;       // phase 5
+        tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562);   // 2*c4
+
+        int z5 = MULTIPLY(z10 + z12, FIX_1_847759065);  // 2*c2
+        tmp10 = MULTIPLY(z12, - FIX_1_082392200) + z5;  // 2*(c2-c6)
+        tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5;  // -2*(c2+c6)
+
+        tmp6 = tmp12 - tmp7;    // phase 2
+        tmp5 = tmp11 - tmp6;
+        tmp4 = tmp10 - tmp5;
+
+        ws[pos+DCTSIZE*0] = tmp0 + tmp7;
+        ws[pos+DCTSIZE*7] = tmp0 - tmp7;
+        ws[pos+DCTSIZE*1] = tmp1 + tmp6;
+        ws[pos+DCTSIZE*6] = tmp1 - tmp6;
+        ws[pos+DCTSIZE*2] = tmp2 + tmp5;
+        ws[pos+DCTSIZE*5] = tmp2 - tmp5;
+        ws[pos+DCTSIZE*3] = tmp3 + tmp4;
+        ws[pos+DCTSIZE*4] = tmp3 - tmp4;
+    }
+    
+    for(int pos = 0; pos < DCTSIZE2; pos += DCTSIZE) {
+        if (ws[pos+1] == 0 && ws[pos+2] == 0 && ws[pos+3] == 0 &&
+               ws[pos+4] == 0 && ws[pos+5] == 0 && ws[pos+6] == 0 &&
+               ws[pos+7] == 0) {
+            int dcval = ws[pos+0];
+            for(int x = 0; x < DCTSIZE; x++) {
+                output[pos+x] = IDESCALE(dcval);
+            }
+            continue;
+        }
+        // Even part
+        int tmp10 = ws[pos+0] + ws[pos+4];
+        int tmp11 = ws[pos+0] - ws[pos+4];
+
+        int tmp13 = ws[pos+2] + ws[pos+6];
+        int tmp12 = MULTIPLY(ws[pos+2] - ws[pos+6], FIX_1_414213562) - tmp13;
+
+        int tmp0 = tmp10 + tmp13;
+        int tmp3 = tmp10 - tmp13;
+        int tmp1 = tmp11 + tmp12;
+        int tmp2 = tmp11 - tmp12;
+
+        // Odd part
+        int z13 = ws[pos+5] + ws[pos+3];
+        int z10 = ws[pos+5] - ws[pos+3];
+        int z11 = ws[pos+1] + ws[pos+7];
+        int z12 = ws[pos+1] - ws[pos+7];
+
+        int tmp7 = z11 + z13;       // phase 5
+        tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562);   // 2*c4
+
+        int z5 = MULTIPLY(z10 + z12, FIX_1_847759065);  // 2*c2
+        tmp10 = MULTIPLY(z12, - FIX_1_082392200) + z5;  // 2*(c2-c6)
+        tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5;  // -2*(c2+c6)
+
+        int tmp6 = tmp12 - tmp7;    // phase 2
+        int tmp5 = tmp11 - tmp6;
+        int tmp4 = tmp10 - tmp5;
+
+        output[pos+0] = IDESCALE(tmp0 + tmp7);
+        output[pos+7] = IDESCALE(tmp0 - tmp7);
+        output[pos+1] = IDESCALE(tmp1 + tmp6);
+        output[pos+6] = IDESCALE(tmp1 - tmp6);
+        output[pos+2] = IDESCALE(tmp2 + tmp5);
+        output[pos+5] = IDESCALE(tmp2 - tmp5);
+        output[pos+3] = IDESCALE(tmp3 + tmp4);
+        output[pos+4] = IDESCALE(tmp3 - tmp4);
+    }
+}