--- /dev/null
+#include "../libzmpeg3.h"
+
+/**********************************************************/
+/* inverse two dimensional DCT, Chen-Wang algorithm */
+/* (cf. IEEE ASSP-32, pp. 803-816, Aug. 1984) */
+/* 32-bit integer arithmetic (8 bit coefficients) */
+/* 11 mults, 29 adds per DCT */
+/* sE, 18.8.91 */
+/**********************************************************/
+/* coefficients extended to 12 bit for IEEE1180-1990 */
+/* compliance sE, 2.1.94 */
+/**********************************************************/
+
+/* this code assumes >> to be a two's-complement arithmetic */
+/* right shift: (-2)>>1 == -1 , (-3)>>1 == -2 */
+
+#define W1 2841 /* 2048*sqrt(2)*cos(1*pi/16) */
+#define W2 2676 /* 2048*sqrt(2)*cos(2*pi/16) */
+#define W3 2408 /* 2048*sqrt(2)*cos(3*pi/16) */
+#define W5 1609 /* 2048*sqrt(2)*cos(5*pi/16) */
+#define W6 1108 /* 2048*sqrt(2)*cos(6*pi/16) */
+#define W7 565 /* 2048*sqrt(2)*cos(7*pi/16) */
+
+/* row (horizontal) IDCT
+ *
+ * 7 pi 1
+ * dst[k] = sum c[l] * src[l] * cos( -- * ( k + - ) * l )
+ * l=0 8 2
+ *
+ * where: c[0] = 128
+ * c[1..7] = 128*sqrt(2)
+ */
+
+static int idct_row(short *blk)
+{
+ int x0, x1, x2, x3, x4, x5, x6, x7, x8;
+
+ /* shortcut */
+ if( !((x1 = blk[4]<<11) | (x2 = blk[6]) | (x3 = blk[2]) |
+ (x4 = blk[1]) | (x5 = blk[7]) | (x6 = blk[5]) | (x7 = blk[3])) ) {
+ blk[0]=blk[1]=blk[2]=blk[3]=blk[4]=blk[5]=blk[6]=blk[7]=blk[0]<<3;
+ return 0;
+ }
+
+ x0 = (blk[0]<<11) + 128; /* for proper rounding in the fourth stage */
+
+ x8 = W7*(x4+x5); /* first stage */
+ x4 = x8 + (W1-W7)*x4;
+ x5 = x8 - (W1+W7)*x5;
+ x8 = W3*(x6+x7);
+ x6 = x8 - (W3-W5)*x6;
+ x7 = x8 - (W3+W5)*x7;
+
+ x8 = x0 + x1; /* second stage */
+ x0 -= x1;
+ x1 = W6*(x3+x2);
+ x2 = x1 - (W2+W6)*x2;
+ x3 = x1 + (W2-W6)*x3;
+ x1 = x4 + x6;
+ x4 -= x6;
+ x6 = x5 + x7;
+ x5 -= x7;
+
+ x7 = x8 + x3; /* third stage */
+ x8 -= x3;
+ x3 = x0 + x2;
+ x0 -= x2;
+ x2 = (181*(x4+x5)+128)>>8;
+ x4 = (181*(x4-x5)+128)>>8;
+
+ blk[0] = (x7+x1)>>8; /* fourth stage */
+ blk[1] = (x3+x2)>>8;
+ blk[2] = (x0+x4)>>8;
+ blk[3] = (x8+x6)>>8;
+ blk[4] = (x8-x6)>>8;
+ blk[5] = (x0-x4)>>8;
+ blk[6] = (x3-x2)>>8;
+ blk[7] = (x7-x1)>>8;
+ return 0;
+}
+
+/* column (vertical) IDCT
+ *
+ * 7 pi 1
+ * dst[8*k] = sum c[l] * src[8*l] * cos( -- * ( k + - ) * l )
+ * l=0 8 2
+ *
+ * where: c[0] = 1/1024
+ * c[1..7] = (1/1024)*sqrt(2)
+ */
+
+static int idct_col(short *blk)
+{
+ int x0, x1, x2, x3, x4, x5, x6, x7, x8;
+
+ /* shortcut */
+ if( !((x1 = (blk[8*4]<<8)) | (x2 = blk[8*6]) | (x3 = blk[8*2]) |
+ (x4 = blk[8*1]) | (x5 = blk[8*7]) | (x6 = blk[8*5]) |
+ (x7 = blk[8 * 3])) ) {
+ blk[8*0] = blk[8*1] = blk[8*2] = blk[8*3] =
+ blk[8*4] = blk[8*5] = blk[8*6] = blk[8*7] = (blk[8*0]+32)>>6;
+ return 0;
+ }
+
+ x0 = (blk[8*0]<<8) + 8192;
+
+ x8 = W7*(x4+x5) + 4; /* first stage */
+ x4 = (x8+(W1-W7)*x4)>>3;
+ x5 = (x8-(W1+W7)*x5)>>3;
+ x8 = W3*(x6+x7) + 4;
+ x6 = (x8-(W3-W5)*x6)>>3;
+ x7 = (x8-(W3+W5)*x7)>>3;
+
+ x8 = x0 + x1; /* second stage */
+ x0 -= x1;
+ x1 = W6*(x3+x2) + 4;
+ x2 = (x1-(W2+W6)*x2)>>3;
+ x3 = (x1+(W2-W6)*x3)>>3;
+ x1 = x4 + x6;
+ x4 -= x6;
+ x6 = x5 + x7;
+ x5 -= x7;
+
+ x7 = x8 + x3; /* third stage */
+ x8 -= x3;
+ x3 = x0 + x2;
+ x0 -= x2;
+ x2 = (181 * (x4+x5) + 128) >> 8;
+ x4 = (181 * (x4-x5) + 128) >> 8;
+
+ blk[8 * 0] = (x7+x1) >> 14; /* fourth stage */
+ blk[8 * 1] = (x3+x2) >> 14;
+ blk[8 * 2] = (x0+x4) >> 14;
+ blk[8 * 3] = (x8+x6) >> 14;
+ blk[8 * 4] = (x8-x6) >> 14;
+ blk[8 * 5] = (x0-x4) >> 14;
+ blk[8 * 6] = (x3-x2) >> 14;
+ blk[8 * 7] = (x7-x1) >> 14;
+ return 0;
+}
+
+
+/* two dimensional inverse discrete cosine transform */
+void zslice_decoder_t::
+idct_conversion(short* block)
+{
+ int i;
+ for( i=0; i<8; ++i )
+ idct_row(block + 8*i);
+ for( i=0; i<8; ++i )
+ idct_col(block + i);
+}
+