Libav
bitstream.c
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1 /*
2  * Common bit i/o utils
3  * Copyright (c) 2000, 2001 Fabrice Bellard
4  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
5  * Copyright (c) 2010 Loren Merritt
6  *
7  * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
8  *
9  * This file is part of Libav.
10  *
11  * Libav is free software; you can redistribute it and/or
12  * modify it under the terms of the GNU Lesser General Public
13  * License as published by the Free Software Foundation; either
14  * version 2.1 of the License, or (at your option) any later version.
15  *
16  * Libav is distributed in the hope that it will be useful,
17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19  * Lesser General Public License for more details.
20  *
21  * You should have received a copy of the GNU Lesser General Public
22  * License along with Libav; if not, write to the Free Software
23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24  */
25 
31 #include "avcodec.h"
32 #include "internal.h"
33 #include "mathops.h"
34 #include "put_bits.h"
35 #include "vlc.h"
36 
37 const uint8_t ff_log2_run[41]={
38  0, 0, 0, 0, 1, 1, 1, 1,
39  2, 2, 2, 2, 3, 3, 3, 3,
40  4, 4, 5, 5, 6, 6, 7, 7,
41  8, 9,10,11,12,13,14,15,
42 16,17,18,19,20,21,22,23,
43 24,
44 };
45 
47 {
48  put_bits(s, s->bit_left & 7, 0);
49 }
50 
51 void avpriv_put_string(PutBitContext *pb, const char *string,
52  int terminate_string)
53 {
54  while (*string) {
55  put_bits(pb, 8, *string);
56  string++;
57  }
58  if (terminate_string)
59  put_bits(pb, 8, 0);
60 }
61 
62 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
63 {
64  int words = length >> 4;
65  int bits = length & 15;
66  int i;
67 
68  if (length == 0)
69  return;
70 
71  if (CONFIG_SMALL || words < 16 || put_bits_count(pb) & 7) {
72  for (i = 0; i < words; i++)
73  put_bits(pb, 16, AV_RB16(src + 2 * i));
74  } else {
75  for (i = 0; put_bits_count(pb) & 31; i++)
76  put_bits(pb, 8, src[i]);
77  flush_put_bits(pb);
78  memcpy(put_bits_ptr(pb), src + i, 2 * words - i);
79  skip_put_bytes(pb, 2 * words - i);
80  }
81 
82  put_bits(pb, bits, AV_RB16(src + 2 * words) >> (16 - bits));
83 }
84 
85 /* VLC decoding */
86 
87 #define GET_DATA(v, table, i, wrap, size) \
88 { \
89  const uint8_t *ptr = (const uint8_t *)table + i * wrap; \
90  switch(size) { \
91  case 1: \
92  v = *(const uint8_t *)ptr; \
93  break; \
94  case 2: \
95  v = *(const uint16_t *)ptr; \
96  break; \
97  default: \
98  v = *(const uint32_t *)ptr; \
99  break; \
100  } \
101 }
102 
103 
104 static int alloc_table(VLC *vlc, int size, int use_static)
105 {
106  int index = vlc->table_size;
107 
108  vlc->table_size += size;
109  if (vlc->table_size > vlc->table_allocated) {
110  int err;
111  if (use_static)
112  return AVERROR_BUG;
113  vlc->table_allocated += (1 << vlc->bits);
114  if ((err = av_reallocp(&vlc->table,
115  sizeof(VLC_TYPE) * 2 *
116  vlc->table_allocated)) < 0) {
117  vlc->table_allocated = 0;
118  vlc->table_size = 0;
119  return err;
120  }
121  }
122  return index;
123 }
124 
125 static av_always_inline uint32_t bitswap_32(uint32_t x)
126 {
127  return (uint32_t)ff_reverse[ x & 0xFF] << 24 |
128  (uint32_t)ff_reverse[(x >> 8) & 0xFF] << 16 |
129  (uint32_t)ff_reverse[(x >> 16) & 0xFF] << 8 |
130  (uint32_t)ff_reverse[ x >> 24];
131 }
132 
133 typedef struct VLCcode {
135  uint16_t symbol;
138  uint32_t code;
139 } VLCcode;
140 
141 static int compare_vlcspec(const void *a, const void *b)
142 {
143  const VLCcode *sa = a, *sb = b;
144  return (sa->code >> 1) - (sb->code >> 1);
145 }
160 static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
161  VLCcode *codes, int flags)
162 {
163  int table_size, table_index, index, code_prefix, symbol, subtable_bits;
164  int i, j, k, n, nb, inc;
165  uint32_t code;
166  VLC_TYPE (*table)[2];
167 
168  table_size = 1 << table_nb_bits;
169  table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
170  ff_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);
171  if (table_index < 0)
172  return table_index;
173  table = &vlc->table[table_index];
174 
175  for (i = 0; i < table_size; i++) {
176  table[i][1] = 0; //bits
177  table[i][0] = -1; //codes
178  }
179 
180  /* first pass: map codes and compute auxiliary table sizes */
181  for (i = 0; i < nb_codes; i++) {
182  n = codes[i].bits;
183  code = codes[i].code;
184  symbol = codes[i].symbol;
185  ff_dlog(NULL, "i=%d n=%d code=0x%x\n", i, n, code);
186  if (n <= table_nb_bits) {
187  /* no need to add another table */
188  j = code >> (32 - table_nb_bits);
189  nb = 1 << (table_nb_bits - n);
190  inc = 1;
191  if (flags & INIT_VLC_LE) {
192  j = bitswap_32(code);
193  inc = 1 << n;
194  }
195  for (k = 0; k < nb; k++) {
196  ff_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n);
197  if (table[j][1] /*bits*/ != 0) {
198  av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
199  return AVERROR_INVALIDDATA;
200  }
201  table[j][1] = n; //bits
202  table[j][0] = symbol;
203  j += inc;
204  }
205  } else {
206  /* fill auxiliary table recursively */
207  n -= table_nb_bits;
208  code_prefix = code >> (32 - table_nb_bits);
209  subtable_bits = n;
210  codes[i].bits = n;
211  codes[i].code = code << table_nb_bits;
212  for (k = i+1; k < nb_codes; k++) {
213  n = codes[k].bits - table_nb_bits;
214  if (n <= 0)
215  break;
216  code = codes[k].code;
217  if (code >> (32 - table_nb_bits) != code_prefix)
218  break;
219  codes[k].bits = n;
220  codes[k].code = code << table_nb_bits;
221  subtable_bits = FFMAX(subtable_bits, n);
222  }
223  subtable_bits = FFMIN(subtable_bits, table_nb_bits);
224  j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;
225  table[j][1] = -subtable_bits;
226  ff_dlog(NULL, "%4x: n=%d (subtable)\n",
227  j, codes[i].bits + table_nb_bits);
228  index = build_table(vlc, subtable_bits, k-i, codes+i, flags);
229  if (index < 0)
230  return index;
231  /* note: realloc has been done, so reload tables */
232  table = &vlc->table[table_index];
233  table[j][0] = index; //code
234  i = k-1;
235  }
236  }
237  return table_index;
238 }
239 
240 
241 /* Build VLC decoding tables suitable for use with get_vlc().
242 
243  'nb_bits' sets the decoding table size (2^nb_bits) entries. The
244  bigger it is, the faster is the decoding. But it should not be too
245  big to save memory and L1 cache. '9' is a good compromise.
246 
247  'nb_codes' : number of vlcs codes
248 
249  'bits' : table which gives the size (in bits) of each vlc code.
250 
251  'codes' : table which gives the bit pattern of of each vlc code.
252 
253  'symbols' : table which gives the values to be returned from get_vlc().
254 
255  'xxx_wrap' : give the number of bytes between each entry of the
256  'bits' or 'codes' tables.
257 
258  'xxx_size' : gives the number of bytes of each entry of the 'bits'
259  or 'codes' tables.
260 
261  'wrap' and 'size' allows to use any memory configuration and types
262  (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
263 
264  'use_static' should be set to 1 for tables, which should be freed
265  with av_free_static(), 0 if ff_free_vlc() will be used.
266 */
267 int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
268  const void *bits, int bits_wrap, int bits_size,
269  const void *codes, int codes_wrap, int codes_size,
270  const void *symbols, int symbols_wrap, int symbols_size,
271  int flags)
272 {
273  VLCcode *buf;
274  int i, j, ret;
275 
276  vlc->bits = nb_bits;
277  if (flags & INIT_VLC_USE_NEW_STATIC) {
278  if (vlc->table_size && vlc->table_size == vlc->table_allocated) {
279  return 0;
280  } else if (vlc->table_size) {
281  return AVERROR_BUG;
282  }
283  } else {
284  vlc->table = NULL;
285  vlc->table_allocated = 0;
286  vlc->table_size = 0;
287  }
288 
289  ff_dlog(NULL, "build table nb_codes=%d\n", nb_codes);
290 
291  buf = av_malloc((nb_codes + 1) * sizeof(VLCcode));
292  if (!buf)
293  return AVERROR(ENOMEM);
294 
295  assert(symbols_size <= 2 || !symbols);
296  j = 0;
297 #define COPY(condition) \
298  for (i = 0; i < nb_codes; i++) { \
299  GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size); \
300  if (!(condition)) \
301  continue; \
302  GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size); \
303  if (flags & INIT_VLC_LE) \
304  buf[j].code = bitswap_32(buf[j].code); \
305  else \
306  buf[j].code <<= 32 - buf[j].bits; \
307  if (symbols) \
308  GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size) \
309  else \
310  buf[j].symbol = i; \
311  j++; \
312  }
313  COPY(buf[j].bits > nb_bits);
314  // qsort is the slowest part of init_vlc, and could probably be improved or avoided
315  qsort(buf, j, sizeof(VLCcode), compare_vlcspec);
316  COPY(buf[j].bits && buf[j].bits <= nb_bits);
317  nb_codes = j;
318 
319  ret = build_table(vlc, nb_bits, nb_codes, buf, flags);
320 
321  av_free(buf);
322  if (ret < 0) {
323  av_freep(&vlc->table);
324  return ret;
325  }
326  if ((flags & INIT_VLC_USE_NEW_STATIC) &&
327  vlc->table_size != vlc->table_allocated)
328  av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n",
329  vlc->table_size, vlc->table_allocated);
330  return 0;
331 }
332 
333 
334 void ff_free_vlc(VLC *vlc)
335 {
336  av_freep(&vlc->table);
337 }
const uint8_t ff_log2_run[41]
Definition: bitstream.c:37
void * av_malloc(size_t size)
Allocate a block of size bytes with alignment suitable for all memory accesses (including vectors if ...
Definition: mem.c:62
int table_size
Definition: vlc.h:29
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:54
int size
av_log(ac->avr, AV_LOG_TRACE, "%d samples - audio_convert: %s to %s (%s)\, len, av_get_sample_fmt_name(ac->in_fmt), av_get_sample_fmt_name(ac->out_fmt), use_generic ? ac->func_descr_generic :ac->func_descr)
void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
Copy the content of src to the bitstream.
Definition: bitstream.c:62
void avpriv_align_put_bits(PutBitContext *s)
Pad the bitstream with zeros up to the next byte boundary.
Definition: bitstream.c:46
#define CONFIG_SMALL
Definition: config.h:405
static int build_table(VLC *vlc, int table_nb_bits, int nb_codes, VLCcode *codes, int flags)
Build VLC decoding tables suitable for use with get_vlc().
Definition: bitstream.c:160
void av_freep(void *arg)
Free a memory block which has been allocated with av_malloc(z)() or av_realloc() and set the pointer ...
Definition: mem.c:202
int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes, const void *bits, int bits_wrap, int bits_size, const void *codes, int codes_wrap, int codes_size, const void *symbols, int symbols_wrap, int symbols_size, int flags)
Definition: bitstream.c:267
uint8_t bits
Definition: crc.c:252
uint8_t
static av_always_inline uint32_t bitswap_32(uint32_t x)
Definition: bitstream.c:125
#define b
Definition: input.c:52
#define COPY(condition)
int av_reallocp(void *ptr, size_t size)
Allocate or reallocate a block of memory.
Definition: mem.c:140
static int flags
Definition: log.c:50
#define src
Definition: vp8dsp.c:254
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:124
static uint8_t * put_bits_ptr(PutBitContext *s)
Return the pointer to the byte where the bitstream writer will put the next bit.
Definition: put_bits.h:199
void av_free(void *ptr)
Free a memory block which has been allocated with av_malloc(z)() or av_realloc(). ...
Definition: mem.c:190
#define AV_RB16
Definition: intreadwrite.h:53
#define AVERROR(e)
Definition: error.h:43
uint32_t code
codeword, with the first bit-to-be-read in the msb (even if intended for a little-endian bitstream re...
Definition: bitstream.c:138
static void put_bits(PutBitContext *s, int n, unsigned int value)
Write up to 31 bits into a bitstream.
Definition: put_bits.h:134
#define FFMAX(a, b)
Definition: common.h:64
Definition: vlc.h:26
static int put_bits_count(PutBitContext *s)
Definition: put_bits.h:67
static void skip_put_bytes(PutBitContext *s, int n)
Skip the given number of bytes.
Definition: put_bits.h:208
#define FFMIN(a, b)
Definition: common.h:66
uint8_t bits
Definition: bitstream.c:134
uint16_t symbol
Definition: bitstream.c:135
static int compare_vlcspec(const void *a, const void *b)
Definition: bitstream.c:141
#define INIT_VLC_LE
Definition: vlc.h:54
int bits
Definition: vlc.h:27
int table_allocated
Definition: vlc.h:29
NULL
Definition: eval.c:55
Libavcodec external API header.
#define ff_dlog(ctx,...)
Definition: internal.h:60
int bit_left
Definition: put_bits.h:37
#define AVERROR_BUG
Bug detected, please report the issue.
Definition: error.h:60
int index
Definition: gxfenc.c:72
common internal api header.
static void flush_put_bits(PutBitContext *s)
Pad the end of the output stream with zeros.
Definition: put_bits.h:83
#define INIT_VLC_USE_NEW_STATIC
Definition: vlc.h:55
VLC_TYPE(* table)[2]
code, bits
Definition: vlc.h:28
void avpriv_put_string(PutBitContext *pb, const char *string, int terminate_string)
Put the string string in the bitstream.
Definition: bitstream.c:51
#define av_always_inline
Definition: attributes.h:40
const uint8_t ff_reverse[256]
Definition: mathtables.c:72
#define VLC_TYPE
Definition: vlc.h:24
void ff_free_vlc(VLC *vlc)
Definition: bitstream.c:334
static int alloc_table(VLC *vlc, int size, int use_static)
Definition: bitstream.c:104
bitstream writer API