jddctmgr.c revision 6ead6aed9ef9420c6d4c5efd170d5ab502e337e5 
1/*
2 * jddctmgr.c
3 *
4 * Copyright (C) 1994-1996, Thomas G. Lane.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
7 *
8 * This file contains the inverse-DCT management logic.
9 * This code selects a particular IDCT implementation to be used,
10 * and it performs related housekeeping chores.  No code in this file
11 * is executed per IDCT step, only during output pass setup.
12 *
13 * Note that the IDCT routines are responsible for performing coefficient
14 * dequantization as well as the IDCT proper.  This module sets up the
15 * dequantization multiplier table needed by the IDCT routine.
16 */
17
18#define JPEG_INTERNALS
19#include "jinclude.h"
20#include "jpeglib.h"
21#include "jdct.h"		/* Private declarations for DCT subsystem */
22
23#ifdef ANDROID_ARMV6_IDCT
24  #undef ANDROID_ARMV6_IDCT
25  #ifdef __arm__
26    #include <machine/cpu-features.h>
27    #if __ARM_ARCH__ >= 6
28      #define ANDROID_ARMV6_IDCT
29    #else
30      #warning "ANDROID_ARMV6_IDCT is disabled"
31    #endif
32  #endif
33#endif
34
35#ifdef ANDROID_ARMV6_IDCT
36
37/* Intentionally declare the prototype with arguments of primitive types instead
38 * of type-defined ones. This will at least generate some warnings if jmorecfg.h
39 * is changed and becomes incompatible with the assembly code.
40 */
41extern void armv6_idct(short *coefs, int *quans, unsigned char **rows, int col);
42
43void jpeg_idct_armv6 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
44		 JCOEFPTR coef_block,
45		 JSAMPARRAY output_buf, JDIMENSION output_col)
46{
47  IFAST_MULT_TYPE *dct_table = (IFAST_MULT_TYPE *)compptr->dct_table;
48  armv6_idct(coef_block, dct_table, output_buf, output_col);
49}
50
51#endif
52
53/*
54 * The decompressor input side (jdinput.c) saves away the appropriate
55 * quantization table for each component at the start of the first scan
56 * involving that component.  (This is necessary in order to correctly
57 * decode files that reuse Q-table slots.)
58 * When we are ready to make an output pass, the saved Q-table is converted
59 * to a multiplier table that will actually be used by the IDCT routine.
60 * The multiplier table contents are IDCT-method-dependent.  To support
61 * application changes in IDCT method between scans, we can remake the
62 * multiplier tables if necessary.
63 * In buffered-image mode, the first output pass may occur before any data
64 * has been seen for some components, and thus before their Q-tables have
65 * been saved away.  To handle this case, multiplier tables are preset
66 * to zeroes; the result of the IDCT will be a neutral gray level.
67 */
68
69
70/* Private subobject for this module */
71
72typedef struct {
73  struct jpeg_inverse_dct pub;	/* public fields */
74
75  /* This array contains the IDCT method code that each multiplier table
76   * is currently set up for, or -1 if it's not yet set up.
77   * The actual multiplier tables are pointed to by dct_table in the
78   * per-component comp_info structures.
79   */
80  int cur_method[MAX_COMPONENTS];
81} my_idct_controller;
82
83typedef my_idct_controller * my_idct_ptr;
84
85
86/* Allocated multiplier tables: big enough for any supported variant */
87
88typedef union {
89  ISLOW_MULT_TYPE islow_array[DCTSIZE2];
90#ifdef DCT_IFAST_SUPPORTED
91  IFAST_MULT_TYPE ifast_array[DCTSIZE2];
92#endif
93#ifdef DCT_FLOAT_SUPPORTED
94  FLOAT_MULT_TYPE float_array[DCTSIZE2];
95#endif
96} multiplier_table;
97
98
99/* The current scaled-IDCT routines require ISLOW-style multiplier tables,
100 * so be sure to compile that code if either ISLOW or SCALING is requested.
101 */
102#ifdef DCT_ISLOW_SUPPORTED
103#define PROVIDE_ISLOW_TABLES
104#else
105#ifdef IDCT_SCALING_SUPPORTED
106#define PROVIDE_ISLOW_TABLES
107#endif
108#endif
109
110
111/*
112 * Prepare for an output pass.
113 * Here we select the proper IDCT routine for each component and build
114 * a matching multiplier table.
115 */
116
117METHODDEF(void)
118start_pass (j_decompress_ptr cinfo)
119{
120  my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
121  int ci, i;
122  jpeg_component_info *compptr;
123  int method = 0;
124  inverse_DCT_method_ptr method_ptr = NULL;
125  JQUANT_TBL * qtbl;
126
127  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
128       ci++, compptr++) {
129    /* Select the proper IDCT routine for this component's scaling */
130    switch (compptr->DCT_scaled_size) {
131#ifdef IDCT_SCALING_SUPPORTED
132    case 1:
133      method_ptr = jpeg_idct_1x1;
134      method = JDCT_ISLOW;	/* jidctred uses islow-style table */
135      break;
136    case 2:
137      method_ptr = jpeg_idct_2x2;
138      method = JDCT_ISLOW;	/* jidctred uses islow-style table */
139      break;
140    case 4:
141      method_ptr = jpeg_idct_4x4;
142      method = JDCT_ISLOW;	/* jidctred uses islow-style table */
143      break;
144#endif
145    case DCTSIZE:
146      switch (cinfo->dct_method) {
147#ifdef ANDROID_ARMV6_IDCT
148      case JDCT_ISLOW:
149      case JDCT_IFAST:
150	method_ptr = jpeg_idct_armv6;
151	method = JDCT_IFAST;
152	break;
153#else /* ANDROID_ARMV6_IDCT */
154#ifdef DCT_ISLOW_SUPPORTED
155      case JDCT_ISLOW:
156	method_ptr = jpeg_idct_islow;
157	method = JDCT_ISLOW;
158	break;
159#endif
160#ifdef DCT_IFAST_SUPPORTED
161      case JDCT_IFAST:
162	method_ptr = jpeg_idct_ifast;
163	method = JDCT_IFAST;
164	break;
165#endif
166#endif /* ANDROID_ARMV6_IDCT */
167#ifdef DCT_FLOAT_SUPPORTED
168      case JDCT_FLOAT:
169	method_ptr = jpeg_idct_float;
170	method = JDCT_FLOAT;
171	break;
172#endif
173      default:
174	ERREXIT(cinfo, JERR_NOT_COMPILED);
175	break;
176      }
177      break;
178    default:
179      ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->DCT_scaled_size);
180      break;
181    }
182    idct->pub.inverse_DCT[ci] = method_ptr;
183    /* Create multiplier table from quant table.
184     * However, we can skip this if the component is uninteresting
185     * or if we already built the table.  Also, if no quant table
186     * has yet been saved for the component, we leave the
187     * multiplier table all-zero; we'll be reading zeroes from the
188     * coefficient controller's buffer anyway.
189     */
190    if (! compptr->component_needed || idct->cur_method[ci] == method)
191      continue;
192    qtbl = compptr->quant_table;
193    if (qtbl == NULL)		/* happens if no data yet for component */
194      continue;
195    idct->cur_method[ci] = method;
196    switch (method) {
197#ifdef PROVIDE_ISLOW_TABLES
198    case JDCT_ISLOW:
199      {
200	/* For LL&M IDCT method, multipliers are equal to raw quantization
201	 * coefficients, but are stored as ints to ensure access efficiency.
202	 */
203	ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
204	for (i = 0; i < DCTSIZE2; i++) {
205	  ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
206	}
207      }
208      break;
209#endif
210#ifdef DCT_IFAST_SUPPORTED
211    case JDCT_IFAST:
212      {
213	/* For AA&N IDCT method, multipliers are equal to quantization
214	 * coefficients scaled by scalefactor[row]*scalefactor[col], where
215	 *   scalefactor[0] = 1
216	 *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
217	 * For integer operation, the multiplier table is to be scaled by
218	 * IFAST_SCALE_BITS.
219	 */
220	IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
221#ifdef ANDROID_ARMV6_IDCT
222	/* Precomputed values scaled up by 15 bits. */
223	static const unsigned short scales[DCTSIZE2] = {
224	  32768, 45451, 42813, 38531, 32768, 25746, 17734,  9041,
225	  45451, 63042, 59384, 53444, 45451, 35710, 24598, 12540,
226	  42813, 59384, 55938, 50343, 42813, 33638, 23170, 11812,
227	  38531, 53444, 50343, 45308, 38531, 30274, 20853, 10631,
228	  32768, 45451, 42813, 38531, 32768, 25746, 17734,  9041,
229	  25746, 35710, 33638, 30274, 25746, 20228, 13933,  7103,
230	  17734, 24598, 23170, 20853, 17734, 13933,  9598,  4893,
231	   9041, 12540, 11812, 10631,  9041,  7103,  4893,  2494,
232	};
233	/* Inverse map of [7, 5, 1, 3, 0, 2, 4, 6]. */
234	static const char orders[DCTSIZE] = {4, 2, 5, 3, 6, 1, 7, 0};
235	/* Reorder the columns after transposing. */
236	for (i = 0; i < DCTSIZE2; ++i) {
237	  int j = ((i & 7) << 3) + orders[i >> 3];
238	  ifmtbl[j] = (qtbl->quantval[i] * scales[i] + 2) >> 2;
239	}
240#else /* ANDROID_ARMV6_IDCT */
241
242#define CONST_BITS 14
243	static const INT16 aanscales[DCTSIZE2] = {
244	  /* precomputed values scaled up by 14 bits */
245	  16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
246	  22725, 31521, 29692, 26722, 22725, 17855, 12299,  6270,
247	  21407, 29692, 27969, 25172, 21407, 16819, 11585,  5906,
248	  19266, 26722, 25172, 22654, 19266, 15137, 10426,  5315,
249	  16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
250	  12873, 17855, 16819, 15137, 12873, 10114,  6967,  3552,
251	   8867, 12299, 11585, 10426,  8867,  6967,  4799,  2446,
252	   4520,  6270,  5906,  5315,  4520,  3552,  2446,  1247
253	};
254	SHIFT_TEMPS
255
256	for (i = 0; i < DCTSIZE2; i++) {
257	  ifmtbl[i] = (IFAST_MULT_TYPE)
258	    DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
259				  (INT32) aanscales[i]),
260		    CONST_BITS-IFAST_SCALE_BITS);
261	}
262#endif /* ANDROID_ARMV6_IDCT */
263      }
264      break;
265#endif
266#ifdef DCT_FLOAT_SUPPORTED
267    case JDCT_FLOAT:
268      {
269	/* For float AA&N IDCT method, multipliers are equal to quantization
270	 * coefficients scaled by scalefactor[row]*scalefactor[col], where
271	 *   scalefactor[0] = 1
272	 *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
273	 */
274	FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
275	int row, col;
276	static const double aanscalefactor[DCTSIZE] = {
277	  1.0, 1.387039845, 1.306562965, 1.175875602,
278	  1.0, 0.785694958, 0.541196100, 0.275899379
279	};
280
281	i = 0;
282	for (row = 0; row < DCTSIZE; row++) {
283	  for (col = 0; col < DCTSIZE; col++) {
284	    fmtbl[i] = (FLOAT_MULT_TYPE)
285	      ((double) qtbl->quantval[i] *
286	       aanscalefactor[row] * aanscalefactor[col]);
287	    i++;
288	  }
289	}
290      }
291      break;
292#endif
293    default:
294      ERREXIT(cinfo, JERR_NOT_COMPILED);
295      break;
296    }
297  }
298}
299
300
301/*
302 * Initialize IDCT manager.
303 */
304
305GLOBAL(void)
306jinit_inverse_dct (j_decompress_ptr cinfo)
307{
308  my_idct_ptr idct;
309  int ci;
310  jpeg_component_info *compptr;
311
312  idct = (my_idct_ptr)
313    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
314				SIZEOF(my_idct_controller));
315  cinfo->idct = (struct jpeg_inverse_dct *) idct;
316  idct->pub.start_pass = start_pass;
317
318  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
319       ci++, compptr++) {
320    /* Allocate and pre-zero a multiplier table for each component */
321    compptr->dct_table =
322      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
323				  SIZEOF(multiplier_table));
324    MEMZERO(compptr->dct_table, SIZEOF(multiplier_table));
325    /* Mark multiplier table not yet set up for any method */
326    idct->cur_method[ci] = -1;
327  }
328}
329