4 * Copyright (C) 2007 Marc Hoffman <marc.hoffman@analog.com>
6 * This file is part of Libav.
8 * Libav is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
13 * Libav is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with Libav; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 void ff_bfin_fdct (int16_t *buf);
25 This implementation works only for 8x8 input. The range of input
26 must be -256 to 255 i.e. 8bit input represented in a 16bit data
27 word. The original data must be sign extended into the 16bit data
34 X(m) = sum (x(n) * cos ((2n+1)*m*pi/16))
38 0 --*-------------*0+7---*-----*0+3-------*-*-------------------> 0
40 1 --*-\---------/-*1+6---*-\-/-*1+2-------*-*-------------------> 4
42 2 --*---\-----/---*2+5---*-/-\-*1-2---------------*-*-----------> 2
44 3 --*-----\-/-----*3+4---*-----*0-3---------------*-*-----------> 6
46 4 --*-----/-\-----*3-4------------*-*4+5--*-----*---------------> 1
48 5 --*---/-----\---*2-5---*-*------*=*4-5----\-/------*-*--------> 5
49 / \ X S4,S4 / X S3,-S3
50 6 --*-/---------\-*1-6---*-*------*=*7-6----/-\------*-*--------> 3
52 --*-------------*0-7------------*-*7+6--*-----*---------------> 7
56 Cn = cos(n*pi/8) used throughout the code.
60 R0, R1, R2, R3, R4, R5, R6,R7, P0, P1, P2, P3, P4, P5, A0, A1.
62 I0, I1, I2, I3, B0, B2, B3, M0, M1, L3 registers and LC0.
64 Input - r0 - pointer to start of int16_t *block
66 Output - The DCT output coefficients in the int16_t *block
69 This code is called from jpeg_encode.
70 R6, R5, R4 if modified should be stored and restored.
73 Performance: (Timer version 0.6.33)
74 Code Size : 240 Bytes.
76 Input Matrix : 8 * 8 * 2 Bytes.
77 Coefficients : 16 Bytes
78 Temporary matrix: 8 * 8 * 2 Bytes.
79 Cycle Count :26+{18+8*(14+2S)}*2 where S -> Stalls
81 -----------------------------------------
82 | Size | Forward DCT | Inverse DCT |
83 -----------------------------------------
84 | 8x8 | 284 Cycles | 311 Cycles |
85 -----------------------------------------
87 Ck = int16(cos(k/16*pi)*32767+.5)/2
93 Sk = int16(sin(k/16*pi)*32767+.5)/2
99 the coefficients are ordered as follows:
106 -----------------------------------------------------------
107 Libav conformance testing results
108 -----------------------------------------------------------
109 dct-test: modified with the following
110 dct_error("BFINfdct", 0, ff_bfin_fdct, fdct, test);
111 produces the following output:
113 libavcodec> ./dct-test
116 2 -131 -6 -48 -36 33 -83 24
117 34 52 -24 -15 5 92 57 143
118 -67 -43 -1 74 -16 5 -71 32
119 -78 106 92 -34 -38 81 20 -18
120 7 -62 40 2 -15 90 -62 -83
121 -83 1 -104 -13 43 -19 7 11
122 -63 31 12 -29 83 72 21 10
123 -17 -63 -15 73 50 -91 159 -14
124 DCT BFINfdct: err_inf=2 err2=0.16425938 syserr=0.00795000 maxout=2098 blockSumErr=27
125 DCT BFINfdct: 92.1 kdct/s
128 #include "libavutil/bfin/asm.h"
134 .short 0x5a82, 0x2d41, 0x187e, 0x3b21, 0x0c7c, 0x3ec5, 0x238e, 0x3537;
144 [--SP] = (R7:4, P5:3); // Push the registers onto the stack.
147 RELOC(r0, P3, dct_coeff);
152 L3 = 16; // L3 is set to 16 to make the coefficient
156 //----------------------------------------------------------------------------
159 * I0, I1, and I2 registers are used to read the input data. I3 register is used
160 * to read the coefficients. P0 and P1 registers are used for writing the output
163 M0 = 12 (X); // All these initializations are used in the
164 M1 = 16 (X); // modification of address offsets.
175 // Prescale the input to get the correct precision.
179 lsetup (.0, .1) LC0 = P3;
181 .0: r1=r0<<3 (v) || r0=[i0++] ;
185 * B0 points to the "in" buffer.
186 * B2 points to "temp" buffer in the first iteration.
189 lsetup (.2, .3) LC0 = P0;
191 I0 = B0; // I0 points to Input Element (0, 0).
192 I1 = B0; // Element 1 and 0 is read in R0.
193 I1 += M0 || R0 = [I0++]; // I1 points to Input Element (0, 6).
194 I2 = I1; // Element 6 is read into R3.H.
195 I2 -= 4 || R3.H = W[I1++]; // I2 points to Input Element (0, 4).
197 I3 = B3; // I3 points to Coefficients.
198 P0 = B2; // P0 points to temporary array Element
200 P1 = B2; // P1 points to temporary array.
201 R7 = [P1++P2] || R2 = [I2++]; // P1 points to temporary array
203 // R7 is a dummy read. X4,X5
205 R3.L = W[I1--]; // X7 is read into R3.L.
206 R1.H = W[I0++]; // X2 is read into R1.H.
210 * X0 = (X0 + X7) / 2.
211 * X1 = (X1 + X6) / 2.
212 * X6 = (X1 - X6) / 2.
213 * X7 = (X0 - X7) / 2.
214 * It reads the data 3 in R1.L.
217 R0 = R0 +|+ R3, R3 = R0 -|- R3 || R1.L = W[I0++] || NOP;
220 * X2 = (X2 + X5) / 2.
221 * X3 = (X3 + X4) / 2.
222 * X4 = (X3 - X4) / 2.
223 * X5 = (X2 - X5) / 2.
224 * R7 = C4 = cos(4*pi/16)
227 R1 = R1 +|+ R2, R2 = R1 -|- R2 (CO) || NOP || R7 = [I3++];
230 * At the end of stage 1 R0 has (1,0), R1 has (2,3), R2 has (4, 5) and
232 * Where the notation (x, y) represents uper/lower half pairs.
241 R0 = R0 +|+ R1, R1 = R0 -|- R1;
243 lsetup (.row0, .row1) LC1 = P2 >> 1; // 1d dct, loops 8x
247 * This is part 2 computation continued.....
248 * A1 = X6 * cos(pi/4)
249 * A0 = X6 * cos(pi/4)
250 * A1 = A1 - X5 * cos(pi/4)
251 * A0 = A0 + X5 * cos(pi/4).
252 * The instruction W[I0] = R3.L is used for packing it to R2.L.
255 A1=R3.H*R7.l, A0=R3.H*R7.l || I1+=M1 || W[I0] = R3.L;
256 R4.H=(A1-=R2.L*R7.l), R4.L=(A0+=R2.L*R7.l) || I2+=M0 || NOP;
258 /* R0 = (X1,X0) R1 = (X2,X3) R4 = (X5, X6). */
261 * A1 = X0 * cos(pi/4)
262 * A0 = X0 * cos(pi/4)
263 * A1 = A1 - X1 * cos(pi/4)
264 * A0 = A0 + X1 * cos(pi/4)
267 A1=R0.L*R7.h, A0=R0.L*R7.h || NOP || R3.H=W[I1++];
268 R5.H=(A1-=R0.H*R7.h),R5.L=(A0+=R0.H*R7.h) || R7=[I3++] || NOP;
271 * A1 = X2 * cos(3pi/8)
272 * A0 = X3 * cos(3pi/8)
273 * A1 = A1 + X3 * cos(pi/8)
274 * A0 = A0 - X2 * cos(pi/8)
276 * R7 = (cos(7pi/8),cos(pi/8))
282 A1=R1.H*R7.L, A0=R1.L*R7.L || W[P0++P3]=R5.L || R2.L=W[I0];
283 R2=R2+|+R4, R4=R2-|-R4 || I0+=4 || R3.L=W[I1--];
284 R6.H=(A1+=R1.L*R7.H),R6.L=(A0 -= R1.H * R7.H) || I0+=4 || R7=[I3++];
286 /* R2 = (X4, X7) R4 = (X5,X6) R5 = (X1, X0) R6 = (X2,X3). */
289 * A1 = X4 * cos(7pi/16)
290 * A0 = X7 * cos(7pi/16)
291 * A1 = A1 + X7 * cos(pi/16)
292 * A0 = A0 - X4 * cos(pi/16)
295 A1=R2.H*R7.L, A0=R2.L*R7.L || W[P0++P3]=R6.H || R0=[I0++];
296 R2.H=(A1+=R2.L*R7.H),R2.L=(A0-=R2.H*R7.H) || W[P0++P3]=R5.H || R7=[I3++];
299 * A1 = X5 * cos(3pi/16)
300 * A0 = X6 * cos(3pi/16)
301 * A1 = A1 + X6 * cos(5pi/16)
302 * A0 = A0 - X5 * cos(5pi/16)
303 * The output values are written.
306 A1=R4.H*R7.H, A0=R4.L*R7.H || W[P0++P2]=R6.L || R1.H=W[I0++];
307 R4.H=(A1+=R4.L*R7.L),R4.L=(A0-=R4.H*R7.L) || W[P0++P4]=R2.L || R1.L=W[I0++];
310 /* Beginning of next stage, **pipelined** + drain and store the
311 rest of the column store. */
313 R0=R0+|+R3,R3=R0-|-R3 || W[P1++P3]=R2.H || R2=[I2++];
314 R1=R1+|+R2,R2=R1-|-R2 (CO) || W[P1++P3]=R4.L || R7=[I3++];
315 .row1: R0=R0+|+R1,R1=R0-|-R1 || W[P1++P5]=R4.H || NOP;
317 // Exchange input with output.
323 (r7:4,p5:3) = [sp++];