FFmpeg  2.6.9
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Modules Pages
bitstream.c
Go to the documentation of this file.
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 FFmpeg.
10  *
11  * FFmpeg 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  * FFmpeg 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 FFmpeg; if not, write to the Free Software
23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24  */
25 
26 /**
27  * @file
28  * bitstream api.
29  */
30 
31 #include "libavutil/atomic.h"
32 #include "libavutil/avassert.h"
33 #include "avcodec.h"
34 #include "mathops.h"
35 #include "get_bits.h"
36 #include "put_bits.h"
37 
38 const uint8_t ff_log2_run[41]={
39  0, 0, 0, 0, 1, 1, 1, 1,
40  2, 2, 2, 2, 3, 3, 3, 3,
41  4, 4, 5, 5, 6, 6, 7, 7,
42  8, 9,10,11,12,13,14,15,
43 16,17,18,19,20,21,22,23,
44 24,
45 };
46 
48 {
49  put_bits(s, s->bit_left & 7, 0);
50 }
51 
52 void avpriv_put_string(PutBitContext *pb, const char *string,
53  int terminate_string)
54 {
55  while (*string) {
56  put_bits(pb, 8, *string);
57  string++;
58  }
59  if (terminate_string)
60  put_bits(pb, 8, 0);
61 }
62 
64 {
65  int words = length >> 4;
66  int bits = length & 15;
67  int i;
68 
69  if (length == 0)
70  return;
71 
72  av_assert0(length <= put_bits_left(pb));
73 
74  if (CONFIG_SMALL || words < 16 || put_bits_count(pb) & 7) {
75  for (i = 0; i < words; i++)
76  put_bits(pb, 16, AV_RB16(src + 2 * i));
77  } else {
78  for (i = 0; put_bits_count(pb) & 31; i++)
79  put_bits(pb, 8, src[i]);
80  flush_put_bits(pb);
81  memcpy(put_bits_ptr(pb), src + i, 2 * words - i);
82  skip_put_bytes(pb, 2 * words - i);
83  }
84 
85  put_bits(pb, bits, AV_RB16(src + 2 * words) >> (16 - bits));
86 }
87 
88 /* VLC decoding */
89 
90 #define GET_DATA(v, table, i, wrap, size) \
91 { \
92  const uint8_t *ptr = (const uint8_t *)table + i * wrap; \
93  switch(size) { \
94  case 1: \
95  v = *(const uint8_t *)ptr; \
96  break; \
97  case 2: \
98  v = *(const uint16_t *)ptr; \
99  break; \
100  default: \
101  v = *(const uint32_t *)ptr; \
102  break; \
103  } \
104 }
105 
106 
107 static int alloc_table(VLC *vlc, int size, int use_static)
108 {
109  int index = vlc->table_size;
110 
111  vlc->table_size += size;
112  if (vlc->table_size > vlc->table_allocated) {
113  if (use_static)
114  abort(); // cannot do anything, init_vlc() is used with too little memory
115  vlc->table_allocated += (1 << vlc->bits);
116  vlc->table = av_realloc_f(vlc->table, vlc->table_allocated, sizeof(VLC_TYPE) * 2);
117  if (!vlc->table) {
118  vlc->table_allocated = 0;
119  vlc->table_size = 0;
120  return AVERROR(ENOMEM);
121  }
122  memset(vlc->table + vlc->table_allocated - (1 << vlc->bits), 0, sizeof(VLC_TYPE) * 2 << vlc->bits);
123  }
124  return index;
125 }
126 
127 static av_always_inline uint32_t bitswap_32(uint32_t x)
128 {
129  return (uint32_t)ff_reverse[ x & 0xFF] << 24 |
130  (uint32_t)ff_reverse[(x >> 8) & 0xFF] << 16 |
131  (uint32_t)ff_reverse[(x >> 16) & 0xFF] << 8 |
132  (uint32_t)ff_reverse[ x >> 24];
133 }
134 
135 typedef struct VLCcode {
137  uint16_t symbol;
138  /** codeword, with the first bit-to-be-read in the msb
139  * (even if intended for a little-endian bitstream reader) */
140  uint32_t code;
141 } VLCcode;
142 
143 static int compare_vlcspec(const void *a, const void *b)
144 {
145  const VLCcode *sa = a, *sb = b;
146  return (sa->code >> 1) - (sb->code >> 1);
147 }
148 /**
149  * Build VLC decoding tables suitable for use with get_vlc().
150  *
151  * @param vlc the context to be initted
152  *
153  * @param table_nb_bits max length of vlc codes to store directly in this table
154  * (Longer codes are delegated to subtables.)
155  *
156  * @param nb_codes number of elements in codes[]
157  *
158  * @param codes descriptions of the vlc codes
159  * These must be ordered such that codes going into the same subtable are contiguous.
160  * Sorting by VLCcode.code is sufficient, though not necessary.
161  */
162 static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
163  VLCcode *codes, int flags)
164 {
165  int table_size, table_index, index, code_prefix, symbol, subtable_bits;
166  int i, j, k, n, nb, inc;
167  uint32_t code;
168  volatile VLC_TYPE (* volatile table)[2]; // the double volatile is needed to prevent a internal compiler error in gcc 4.2
169 
170  table_size = 1 << table_nb_bits;
171  if (table_nb_bits > 30)
172  return -1;
173  table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
174  av_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);
175  if (table_index < 0)
176  return table_index;
177  table = (volatile VLC_TYPE (*)[2])&vlc->table[table_index];
178 
179  /* first pass: map codes and compute auxiliary table sizes */
180  for (i = 0; i < nb_codes; i++) {
181  n = codes[i].bits;
182  code = codes[i].code;
183  symbol = codes[i].symbol;
184  av_dlog(NULL, "i=%d n=%d code=0x%x\n", i, n, code);
185  if (n <= table_nb_bits) {
186  /* no need to add another table */
187  j = code >> (32 - table_nb_bits);
188  nb = 1 << (table_nb_bits - n);
189  inc = 1;
190  if (flags & INIT_VLC_LE) {
191  j = bitswap_32(code);
192  inc = 1 << n;
193  }
194  for (k = 0; k < nb; k++) {
195  int bits = table[j][1];
196  av_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n);
197  if (bits != 0 && bits != n) {
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  av_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 = (volatile VLC_TYPE (*)[2])&vlc->table[table_index];
233  table[j][0] = index; //code
234  i = k-1;
235  }
236  }
237 
238  for (i = 0; i < table_size; i++) {
239  if (table[i][1] == 0) //bits
240  table[i][0] = -1; //codes
241  }
242 
243  return table_index;
244 }
245 
246 
247 /* Build VLC decoding tables suitable for use with get_vlc().
248 
249  'nb_bits' set thee decoding table size (2^nb_bits) entries. The
250  bigger it is, the faster is the decoding. But it should not be too
251  big to save memory and L1 cache. '9' is a good compromise.
252 
253  'nb_codes' : number of vlcs codes
254 
255  'bits' : table which gives the size (in bits) of each vlc code.
256 
257  'codes' : table which gives the bit pattern of of each vlc code.
258 
259  'symbols' : table which gives the values to be returned from get_vlc().
260 
261  'xxx_wrap' : give the number of bytes between each entry of the
262  'bits' or 'codes' tables.
263 
264  'xxx_size' : gives the number of bytes of each entry of the 'bits'
265  or 'codes' tables.
266 
267  'wrap' and 'size' allows to use any memory configuration and types
268  (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
269 
270  'use_static' should be set to 1 for tables, which should be freed
271  with av_free_static(), 0 if ff_free_vlc() will be used.
272 */
273 int ff_init_vlc_sparse(VLC *vlc_arg, int nb_bits, int nb_codes,
274  const void *bits, int bits_wrap, int bits_size,
275  const void *codes, int codes_wrap, int codes_size,
276  const void *symbols, int symbols_wrap, int symbols_size,
277  int flags)
278 {
279  VLCcode *buf;
280  int i, j, ret;
281  VLCcode localbuf[1500]; // the maximum currently needed is 1296 by rv34
282  VLC localvlc, *vlc;
283 
284  vlc = vlc_arg;
285  vlc->bits = nb_bits;
286  if (flags & INIT_VLC_USE_NEW_STATIC) {
287  av_assert0(nb_codes + 1 <= FF_ARRAY_ELEMS(localbuf));
288  buf = localbuf;
289  localvlc = *vlc_arg;
290  vlc = &localvlc;
291  vlc->table_size = 0;
292  } else {
293  vlc->table = NULL;
294  vlc->table_allocated = 0;
295  vlc->table_size = 0;
296 
297  buf = av_malloc_array((nb_codes + 1), sizeof(VLCcode));
298  if (!buf)
299  return AVERROR(ENOMEM);
300  }
301 
302 
303  av_assert0(symbols_size <= 2 || !symbols);
304  j = 0;
305 #define COPY(condition)\
306  for (i = 0; i < nb_codes; i++) { \
307  GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size); \
308  if (!(condition)) \
309  continue; \
310  if (buf[j].bits > 3*nb_bits || buf[j].bits>32) { \
311  av_log(NULL, AV_LOG_ERROR, "Too long VLC (%d) in init_vlc\n", buf[j].bits);\
312  if (!(flags & INIT_VLC_USE_NEW_STATIC)) \
313  av_free(buf); \
314  return -1; \
315  } \
316  GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size); \
317  if (buf[j].code >= (1LL<<buf[j].bits)) { \
318  av_log(NULL, AV_LOG_ERROR, "Invalid code in init_vlc\n"); \
319  if (!(flags & INIT_VLC_USE_NEW_STATIC)) \
320  av_free(buf); \
321  return -1; \
322  } \
323  if (flags & INIT_VLC_LE) \
324  buf[j].code = bitswap_32(buf[j].code); \
325  else \
326  buf[j].code <<= 32 - buf[j].bits; \
327  if (symbols) \
328  GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size) \
329  else \
330  buf[j].symbol = i; \
331  j++; \
332  }
333  COPY(buf[j].bits > nb_bits);
334  // qsort is the slowest part of init_vlc, and could probably be improved or avoided
335  qsort(buf, j, sizeof(VLCcode), compare_vlcspec);
336  COPY(buf[j].bits && buf[j].bits <= nb_bits);
337  nb_codes = j;
338 
339  ret = build_table(vlc, nb_bits, nb_codes, buf, flags);
340 
341  if (flags & INIT_VLC_USE_NEW_STATIC) {
342  if(vlc->table_size != vlc->table_allocated)
343  av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
344 
345  av_assert0(ret >= 0);
346  *vlc_arg = *vlc;
347  } else {
348  av_free(buf);
349  if (ret < 0) {
350  av_freep(&vlc->table);
351  return ret;
352  }
353  }
354  return 0;
355 }
356 
357 
358 void ff_free_vlc(VLC *vlc)
359 {
360  av_freep(&vlc->table);
361 }
#define NULL
Definition: coverity.c:32
const uint8_t ff_log2_run[41]
Definition: bitstream.c:38
int table_size
Definition: get_bits.h:66
const char * s
Definition: avisynth_c.h:669
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
#define av_realloc_f(p, o, n)
static void put_bits(Jpeg2000EncoderContext *s, int val, int n)
put n times val bit
Definition: j2kenc.c:198
int ff_init_vlc_sparse(VLC *vlc_arg, 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:273
const char * b
Definition: vf_curves.c:109
void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
Copy the content of src to the bitstream.
Definition: bitstream.c:63
void avpriv_align_put_bits(PutBitContext *s)
Pad the bitstream with zeros up to the next byte boundary.
Definition: bitstream.c:47
#define CONFIG_SMALL
Definition: config.h:458
#define VLC_TYPE
Definition: get_bits.h:61
#define FF_ARRAY_ELEMS(a)
av_dlog(ac->avr,"%d samples - audio_convert: %s to %s (%s)\n", 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)
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:162
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
uint8_t bits
Definition: crc.c:295
uint8_t
static av_always_inline uint32_t bitswap_32(uint32_t x)
Definition: bitstream.c:127
#define COPY(condition)
bitstream reader API header.
ptrdiff_t size
Definition: opengl_enc.c:101
#define av_log(a,...)
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:175
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:227
static int put_bits_left(PutBitContext *s)
Definition: put_bits.h:93
#define AV_RB16
Definition: intreadwrite.h:53
#define AVERROR(e)
Definition: error.h:43
static const struct endianess table[]
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:140
simple assert() macros that are a bit more flexible than ISO C assert().
GLsizei GLsizei * length
Definition: opengl_enc.c:115
#define FFMAX(a, b)
Definition: common.h:79
Libavcodec external API header.
Definition: get_bits.h:63
static int put_bits_count(PutBitContext *s)
Definition: put_bits.h:85
static void skip_put_bytes(PutBitContext *s, int n)
Skip the given number of bytes.
Definition: put_bits.h:236
#define FFMIN(a, b)
Definition: common.h:81
ret
Definition: avfilter.c:974
uint8_t bits
Definition: bitstream.c:136
uint16_t symbol
Definition: bitstream.c:137
int n
Definition: avisynth_c.h:589
static int compare_vlcspec(const void *a, const void *b)
Definition: bitstream.c:143
#define INIT_VLC_USE_NEW_STATIC
Definition: get_bits.h:474
int bits
Definition: get_bits.h:64
int table_allocated
Definition: get_bits.h:66
AVS_Value src
Definition: avisynth_c.h:524
int bit_left
Definition: put_bits.h:37
void * buf
Definition: avisynth_c.h:595
#define INIT_VLC_LE
Definition: get_bits.h:473
int index
Definition: gxfenc.c:89
static int flags
Definition: cpu.c:47
static void flush_put_bits(PutBitContext *s)
Pad the end of the output stream with zeros.
Definition: put_bits.h:101
#define av_free(p)
VLC_TYPE(* table)[2]
code, bits
Definition: get_bits.h:65
void avpriv_put_string(PutBitContext *pb, const char *string, int terminate_string)
Put the string string in the bitstream.
Definition: bitstream.c:52
#define av_freep(p)
#define av_always_inline
Definition: attributes.h:37
const uint8_t ff_reverse[256]
Definition: mathtables.c:74
#define av_malloc_array(a, b)
void ff_free_vlc(VLC *vlc)
Definition: bitstream.c:358
for(j=16;j >0;--j)
static int alloc_table(VLC *vlc, int size, int use_static)
Definition: bitstream.c:107
bitstream writer API