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/media/libtheora/lib/idct.c

http://github.com/zpao/v8monkey
C | 329 lines | 155 code | 10 blank | 164 comment | 14 complexity | 5e28c0449ab575fe25f93d00131b37e2 MD5 | raw file
  1/********************************************************************
  2 *                                                                  *
  3 * THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE.   *
  4 * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
  5 * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
  6 * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
  7 *                                                                  *
  8 * THE Theora SOURCE CODE IS COPYRIGHT (C) 2002-2009                *
  9 * by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
 10 *                                                                  *
 11 ********************************************************************
 12
 13  function:
 14    last mod: $Id: idct.c 17410 2010-09-21 21:53:48Z tterribe $
 15
 16 ********************************************************************/
 17
 18#include <string.h>
 19#include "internal.h"
 20#include "dct.h"
 21
 22/*Performs an inverse 8 point Type-II DCT transform.
 23  The output is scaled by a factor of 2 relative to the orthonormal version of
 24   the transform.
 25  _y: The buffer to store the result in.
 26      Data will be placed in every 8th entry (e.g., in a column of an 8x8
 27       block).
 28  _x: The input coefficients.
 29      The first 8 entries are used (e.g., from a row of an 8x8 block).*/
 30static void idct8(ogg_int16_t *_y,const ogg_int16_t _x[8]){
 31  ogg_int32_t t[8];
 32  ogg_int32_t r;
 33  /*Stage 1:*/
 34  /*0-1 butterfly.*/
 35  t[0]=OC_C4S4*(ogg_int16_t)(_x[0]+_x[4])>>16;
 36  t[1]=OC_C4S4*(ogg_int16_t)(_x[0]-_x[4])>>16;
 37  /*2-3 rotation by 6pi/16.*/
 38  t[2]=(OC_C6S2*_x[2]>>16)-(OC_C2S6*_x[6]>>16);
 39  t[3]=(OC_C2S6*_x[2]>>16)+(OC_C6S2*_x[6]>>16);
 40  /*4-7 rotation by 7pi/16.*/
 41  t[4]=(OC_C7S1*_x[1]>>16)-(OC_C1S7*_x[7]>>16);
 42  /*5-6 rotation by 3pi/16.*/
 43  t[5]=(OC_C3S5*_x[5]>>16)-(OC_C5S3*_x[3]>>16);
 44  t[6]=(OC_C5S3*_x[5]>>16)+(OC_C3S5*_x[3]>>16);
 45  t[7]=(OC_C1S7*_x[1]>>16)+(OC_C7S1*_x[7]>>16);
 46  /*Stage 2:*/
 47  /*4-5 butterfly.*/
 48  r=t[4]+t[5];
 49  t[5]=OC_C4S4*(ogg_int16_t)(t[4]-t[5])>>16;
 50  t[4]=r;
 51  /*7-6 butterfly.*/
 52  r=t[7]+t[6];
 53  t[6]=OC_C4S4*(ogg_int16_t)(t[7]-t[6])>>16;
 54  t[7]=r;
 55  /*Stage 3:*/
 56  /*0-3 butterfly.*/
 57  r=t[0]+t[3];
 58  t[3]=t[0]-t[3];
 59  t[0]=r;
 60  /*1-2 butterfly.*/
 61  r=t[1]+t[2];
 62  t[2]=t[1]-t[2];
 63  t[1]=r;
 64  /*6-5 butterfly.*/
 65  r=t[6]+t[5];
 66  t[5]=t[6]-t[5];
 67  t[6]=r;
 68  /*Stage 4:*/
 69  /*0-7 butterfly.*/
 70  _y[0<<3]=(ogg_int16_t)(t[0]+t[7]);
 71  /*1-6 butterfly.*/
 72  _y[1<<3]=(ogg_int16_t)(t[1]+t[6]);
 73  /*2-5 butterfly.*/
 74  _y[2<<3]=(ogg_int16_t)(t[2]+t[5]);
 75  /*3-4 butterfly.*/
 76  _y[3<<3]=(ogg_int16_t)(t[3]+t[4]);
 77  _y[4<<3]=(ogg_int16_t)(t[3]-t[4]);
 78  _y[5<<3]=(ogg_int16_t)(t[2]-t[5]);
 79  _y[6<<3]=(ogg_int16_t)(t[1]-t[6]);
 80  _y[7<<3]=(ogg_int16_t)(t[0]-t[7]);
 81}
 82
 83/*Performs an inverse 8 point Type-II DCT transform.
 84  The output is scaled by a factor of 2 relative to the orthonormal version of
 85   the transform.
 86  _y: The buffer to store the result in.
 87      Data will be placed in every 8th entry (e.g., in a column of an 8x8
 88       block).
 89  _x: The input coefficients.
 90      Only the first 4 entries are used.
 91      The other 4 are assumed to be 0.*/
 92static void idct8_4(ogg_int16_t *_y,const ogg_int16_t _x[8]){
 93  ogg_int32_t t[8];
 94  ogg_int32_t r;
 95  /*Stage 1:*/
 96  t[0]=OC_C4S4*_x[0]>>16;
 97  t[2]=OC_C6S2*_x[2]>>16;
 98  t[3]=OC_C2S6*_x[2]>>16;
 99  t[4]=OC_C7S1*_x[1]>>16;
100  t[5]=-(OC_C5S3*_x[3]>>16);
101  t[6]=OC_C3S5*_x[3]>>16;
102  t[7]=OC_C1S7*_x[1]>>16;
103  /*Stage 2:*/
104  r=t[4]+t[5];
105  t[5]=OC_C4S4*(ogg_int16_t)(t[4]-t[5])>>16;
106  t[4]=r;
107  r=t[7]+t[6];
108  t[6]=OC_C4S4*(ogg_int16_t)(t[7]-t[6])>>16;
109  t[7]=r;
110  /*Stage 3:*/
111  t[1]=t[0]+t[2];
112  t[2]=t[0]-t[2];
113  r=t[0]+t[3];
114  t[3]=t[0]-t[3];
115  t[0]=r;
116  r=t[6]+t[5];
117  t[5]=t[6]-t[5];
118  t[6]=r;
119  /*Stage 4:*/
120  _y[0<<3]=(ogg_int16_t)(t[0]+t[7]);
121  _y[1<<3]=(ogg_int16_t)(t[1]+t[6]);
122  _y[2<<3]=(ogg_int16_t)(t[2]+t[5]);
123  _y[3<<3]=(ogg_int16_t)(t[3]+t[4]);
124  _y[4<<3]=(ogg_int16_t)(t[3]-t[4]);
125  _y[5<<3]=(ogg_int16_t)(t[2]-t[5]);
126  _y[6<<3]=(ogg_int16_t)(t[1]-t[6]);
127  _y[7<<3]=(ogg_int16_t)(t[0]-t[7]);
128}
129
130/*Performs an inverse 8 point Type-II DCT transform.
131  The output is scaled by a factor of 2 relative to the orthonormal version of
132   the transform.
133  _y: The buffer to store the result in.
134      Data will be placed in every 8th entry (e.g., in a column of an 8x8
135       block).
136  _x: The input coefficients.
137      Only the first 3 entries are used.
138      The other 5 are assumed to be 0.*/
139static void idct8_3(ogg_int16_t *_y,const ogg_int16_t _x[8]){
140  ogg_int32_t t[8];
141  ogg_int32_t r;
142  /*Stage 1:*/
143  t[0]=OC_C4S4*_x[0]>>16;
144  t[2]=OC_C6S2*_x[2]>>16;
145  t[3]=OC_C2S6*_x[2]>>16;
146  t[4]=OC_C7S1*_x[1]>>16;
147  t[7]=OC_C1S7*_x[1]>>16;
148  /*Stage 2:*/
149  t[5]=OC_C4S4*t[4]>>16;
150  t[6]=OC_C4S4*t[7]>>16;
151  /*Stage 3:*/
152  t[1]=t[0]+t[2];
153  t[2]=t[0]-t[2];
154  r=t[0]+t[3];
155  t[3]=t[0]-t[3];
156  t[0]=r;
157  r=t[6]+t[5];
158  t[5]=t[6]-t[5];
159  t[6]=r;
160  /*Stage 4:*/
161  _y[0<<3]=(ogg_int16_t)(t[0]+t[7]);
162  _y[1<<3]=(ogg_int16_t)(t[1]+t[6]);
163  _y[2<<3]=(ogg_int16_t)(t[2]+t[5]);
164  _y[3<<3]=(ogg_int16_t)(t[3]+t[4]);
165  _y[4<<3]=(ogg_int16_t)(t[3]-t[4]);
166  _y[5<<3]=(ogg_int16_t)(t[2]-t[5]);
167  _y[6<<3]=(ogg_int16_t)(t[1]-t[6]);
168  _y[7<<3]=(ogg_int16_t)(t[0]-t[7]);
169}
170
171/*Performs an inverse 8 point Type-II DCT transform.
172  The output is scaled by a factor of 2 relative to the orthonormal version of
173   the transform.
174  _y: The buffer to store the result in.
175      Data will be placed in every 8th entry (e.g., in a column of an 8x8
176       block).
177  _x: The input coefficients.
178      Only the first 2 entries are used.
179      The other 6 are assumed to be 0.*/
180static void idct8_2(ogg_int16_t *_y,const ogg_int16_t _x[8]){
181  ogg_int32_t t[8];
182  ogg_int32_t r;
183  /*Stage 1:*/
184  t[0]=OC_C4S4*_x[0]>>16;
185  t[4]=OC_C7S1*_x[1]>>16;
186  t[7]=OC_C1S7*_x[1]>>16;
187  /*Stage 2:*/
188  t[5]=OC_C4S4*t[4]>>16;
189  t[6]=OC_C4S4*t[7]>>16;
190  /*Stage 3:*/
191  r=t[6]+t[5];
192  t[5]=t[6]-t[5];
193  t[6]=r;
194  /*Stage 4:*/
195  _y[0<<3]=(ogg_int16_t)(t[0]+t[7]);
196  _y[1<<3]=(ogg_int16_t)(t[0]+t[6]);
197  _y[2<<3]=(ogg_int16_t)(t[0]+t[5]);
198  _y[3<<3]=(ogg_int16_t)(t[0]+t[4]);
199  _y[4<<3]=(ogg_int16_t)(t[0]-t[4]);
200  _y[5<<3]=(ogg_int16_t)(t[0]-t[5]);
201  _y[6<<3]=(ogg_int16_t)(t[0]-t[6]);
202  _y[7<<3]=(ogg_int16_t)(t[0]-t[7]);
203}
204
205/*Performs an inverse 8 point Type-II DCT transform.
206  The output is scaled by a factor of 2 relative to the orthonormal version of
207   the transform.
208  _y: The buffer to store the result in.
209      Data will be placed in every 8th entry (e.g., in a column of an 8x8
210       block).
211  _x: The input coefficients.
212      Only the first entry is used.
213      The other 7 are assumed to be 0.*/
214static void idct8_1(ogg_int16_t *_y,const ogg_int16_t _x[1]){
215  _y[0<<3]=_y[1<<3]=_y[2<<3]=_y[3<<3]=
216   _y[4<<3]=_y[5<<3]=_y[6<<3]=_y[7<<3]=(ogg_int16_t)(OC_C4S4*_x[0]>>16);
217}
218
219/*Performs an inverse 8x8 Type-II DCT transform.
220  The input is assumed to be scaled by a factor of 4 relative to orthonormal
221   version of the transform.
222  All coefficients but the first 3 in zig-zag scan order are assumed to be 0:
223   x  x  0  0  0  0  0  0
224   x  0  0  0  0  0  0  0
225   0  0  0  0  0  0  0  0
226   0  0  0  0  0  0  0  0
227   0  0  0  0  0  0  0  0
228   0  0  0  0  0  0  0  0
229   0  0  0  0  0  0  0  0
230   0  0  0  0  0  0  0  0
231  _y: The buffer to store the result in.
232      This may be the same as _x.
233  _x: The input coefficients.*/
234static void oc_idct8x8_3(ogg_int16_t _y[64],ogg_int16_t _x[64]){
235  ogg_int16_t w[64];
236  int         i;
237  /*Transform rows of x into columns of w.*/
238  idct8_2(w,_x);
239  idct8_1(w+1,_x+8);
240  /*Transform rows of w into columns of y.*/
241  for(i=0;i<8;i++)idct8_2(_y+i,w+i*8);
242  /*Adjust for the scale factor.*/
243  for(i=0;i<64;i++)_y[i]=(ogg_int16_t)(_y[i]+8>>4);
244  /*Clear input data for next block (decoder only).*/
245  if(_x!=_y)_x[0]=_x[1]=_x[8]=0;
246}
247
248/*Performs an inverse 8x8 Type-II DCT transform.
249  The input is assumed to be scaled by a factor of 4 relative to orthonormal
250   version of the transform.
251  All coefficients but the first 10 in zig-zag scan order are assumed to be 0:
252   x  x  x  x  0  0  0  0
253   x  x  x  0  0  0  0  0
254   x  x  0  0  0  0  0  0
255   x  0  0  0  0  0  0  0
256   0  0  0  0  0  0  0  0
257   0  0  0  0  0  0  0  0
258   0  0  0  0  0  0  0  0
259   0  0  0  0  0  0  0  0
260  _y: The buffer to store the result in.
261      This may be the same as _x.
262  _x: The input coefficients.*/
263static void oc_idct8x8_10(ogg_int16_t _y[64],ogg_int16_t _x[64]){
264  ogg_int16_t w[64];
265  int         i;
266  /*Transform rows of x into columns of w.*/
267  idct8_4(w,_x);
268  idct8_3(w+1,_x+8);
269  idct8_2(w+2,_x+16);
270  idct8_1(w+3,_x+24);
271  /*Transform rows of w into columns of y.*/
272  for(i=0;i<8;i++)idct8_4(_y+i,w+i*8);
273  /*Adjust for the scale factor.*/
274  for(i=0;i<64;i++)_y[i]=(ogg_int16_t)(_y[i]+8>>4);
275  /*Clear input data for next block (decoder only).*/
276  if(_x!=_y)_x[0]=_x[1]=_x[2]=_x[3]=_x[8]=_x[9]=_x[10]=_x[16]=_x[17]=_x[24]=0;
277}
278
279/*Performs an inverse 8x8 Type-II DCT transform.
280  The input is assumed to be scaled by a factor of 4 relative to orthonormal
281   version of the transform.
282  _y: The buffer to store the result in.
283      This may be the same as _x.
284  _x: The input coefficients.*/
285static void oc_idct8x8_slow(ogg_int16_t _y[64],ogg_int16_t _x[64]){
286  ogg_int16_t w[64];
287  int         i;
288  /*Transform rows of x into columns of w.*/
289  for(i=0;i<8;i++)idct8(w+i,_x+i*8);
290  /*Transform rows of w into columns of y.*/
291  for(i=0;i<8;i++)idct8(_y+i,w+i*8);
292  /*Adjust for the scale factor.*/
293  for(i=0;i<64;i++)_y[i]=(ogg_int16_t)(_y[i]+8>>4);
294  if(_x!=_y)for(i=0;i<64;i++)_x[i]=0;
295}
296
297/*Performs an inverse 8x8 Type-II DCT transform.
298  The input is assumed to be scaled by a factor of 4 relative to orthonormal
299   version of the transform.*/
300void oc_idct8x8_c(ogg_int16_t _y[64],ogg_int16_t _x[64],int _last_zzi){
301  /*_last_zzi is subtly different from an actual count of the number of
302     coefficients we decoded for this block.
303    It contains the value of zzi BEFORE the final token in the block was
304     decoded.
305    In most cases this is an EOB token (the continuation of an EOB run from a
306     previous block counts), and so this is the same as the coefficient count.
307    However, in the case that the last token was NOT an EOB token, but filled
308     the block up with exactly 64 coefficients, _last_zzi will be less than 64.
309    Provided the last token was not a pure zero run, the minimum value it can
310     be is 46, and so that doesn't affect any of the cases in this routine.
311    However, if the last token WAS a pure zero run of length 63, then _last_zzi
312     will be 1 while the number of coefficients decoded is 64.
313    Thus, we will trigger the following special case, where the real
314     coefficient count would not.
315    Note also that a zero run of length 64 will give _last_zzi a value of 0,
316     but we still process the DC coefficient, which might have a non-zero value
317     due to DC prediction.
318    Although convoluted, this is arguably the correct behavior: it allows us to
319     use a smaller transform when the block ends with a long zero run instead
320     of a normal EOB token.
321    It could be smarter... multiple separate zero runs at the end of a block
322     will fool it, but an encoder that generates these really deserves what it
323     gets.
324    Needless to say we inherited this approach from VP3.*/
325  /*Then perform the iDCT.*/
326  if(_last_zzi<=3)oc_idct8x8_3(_y,_x);
327  else if(_last_zzi<=10)oc_idct8x8_10(_y,_x);
328  else oc_idct8x8_slow(_y,_x);
329}