/* * Common bit i/o utils * Copyright (c) 2000, 2001 Fabrice Bellard * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at> * Copyright (c) 2010 Loren Merritt * * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at> * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file * bitstream api. */ #include "avcodec.h" #include "get_bits.h" #include "put_bits.h" const uint8_t ff_log2_run[41]={ 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 9,10,11,12,13,14,15, 16,17,18,19,20,21,22,23, 24, }; void align_put_bits(PutBitContext *s) { #ifdef ALT_BITSTREAM_WRITER put_bits(s,( - s->index) & 7,0); #else put_bits(s,s->bit_left & 7,0); #endif } void ff_put_string(PutBitContext *pb, const char *string, int terminate_string) { while(*string){ put_bits(pb, 8, *string); string++; } if(terminate_string) put_bits(pb, 8, 0); } void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length) { int words= length>>4; int bits= length&15; int i; if(length==0) return; if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){ for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i)); }else{ for(i=0; put_bits_count(pb)&31; i++) put_bits(pb, 8, src[i]); flush_put_bits(pb); memcpy(put_bits_ptr(pb), src+i, 2*words-i); skip_put_bytes(pb, 2*words-i); } put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits)); } /* VLC decoding */ //#define DEBUG_VLC #define GET_DATA(v, table, i, wrap, size) \ {\ const uint8_t *ptr = (const uint8_t *)table + i * wrap;\ switch(size) {\ case 1:\ v = *(const uint8_t *)ptr;\ break;\ case 2:\ v = *(const uint16_t *)ptr;\ break;\ default:\ v = *(const uint32_t *)ptr;\ break;\ }\ } static int alloc_table(VLC *vlc, int size, int use_static) { int index; index = vlc->table_size; vlc->table_size += size; if (vlc->table_size > vlc->table_allocated) { if(use_static) abort(); //cant do anything, init_vlc() is used with too little memory vlc->table_allocated += (1 << vlc->bits); vlc->table = av_realloc(vlc->table, sizeof(VLC_TYPE) * 2 * vlc->table_allocated); if (!vlc->table) return -1; } return index; } static av_always_inline uint32_t bitswap_32(uint32_t x) { return av_reverse[x&0xFF]<<24 | av_reverse[(x>>8)&0xFF]<<16 | av_reverse[(x>>16)&0xFF]<<8 | av_reverse[x>>24]; } typedef struct { uint8_t bits; uint16_t symbol; /** codeword, with the first bit-to-be-read in the msb * (even if intended for a little-endian bitstream reader) */ uint32_t code; } VLCcode; static int compare_vlcspec(const void *a, const void *b) { const VLCcode *sa=a, *sb=b; return (sa->code >> 1) - (sb->code >> 1); } /** * Build VLC decoding tables suitable for use with get_vlc(). * * @param vlc the context to be initted * * @param table_nb_bits max length of vlc codes to store directly in this table * (Longer codes are delegated to subtables.) * * @param nb_codes number of elements in codes[] * * @param codes descriptions of the vlc codes * These must be ordered such that codes going into the same subtable are contiguous. * Sorting by VLCcode.code is sufficient, though not necessary. */ static int build_table(VLC *vlc, int table_nb_bits, int nb_codes, VLCcode *codes, int flags) { int table_size, table_index, index, code_prefix, symbol, subtable_bits; int i, j, k, n, nb, inc; uint32_t code; VLC_TYPE (*table)[2]; table_size = 1 << table_nb_bits; table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC); #ifdef DEBUG_VLC av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d\n", table_index, table_size); #endif if (table_index < 0) return -1; table = &vlc->table[table_index]; for (i = 0; i < table_size; i++) { table[i][1] = 0; //bits table[i][0] = -1; //codes } /* first pass: map codes and compute auxillary table sizes */ for (i = 0; i < nb_codes; i++) { n = codes[i].bits; code = codes[i].code; symbol = codes[i].symbol; #if defined(DEBUG_VLC) && 0 av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code); #endif if (n <= table_nb_bits) { /* no need to add another table */ j = code >> (32 - table_nb_bits); nb = 1 << (table_nb_bits - n); inc = 1; if (flags & INIT_VLC_LE) { j = bitswap_32(code); inc = 1 << n; } for (k = 0; k < nb; k++) { #ifdef DEBUG_VLC av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n", j, i, n); #endif if (table[j][1] /*bits*/ != 0) { av_log(NULL, AV_LOG_ERROR, "incorrect codes\n"); return -1; } table[j][1] = n; //bits table[j][0] = symbol; j += inc; } } else { /* fill auxiliary table recursively */ n -= table_nb_bits; code_prefix = code >> (32 - table_nb_bits); subtable_bits = n; codes[i].bits = n; codes[i].code = code << table_nb_bits; for (k = i+1; k < nb_codes; k++) { n = codes[k].bits - table_nb_bits; if (n <= 0) break; code = codes[k].code; if (code >> (32 - table_nb_bits) != code_prefix) break; codes[k].bits = n; codes[k].code = code << table_nb_bits; subtable_bits = FFMAX(subtable_bits, n); } subtable_bits = FFMIN(subtable_bits, table_nb_bits); j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix; table[j][1] = -subtable_bits; #ifdef DEBUG_VLC av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n", j, codes[i].bits + table_nb_bits); #endif index = build_table(vlc, subtable_bits, k-i, codes+i, flags); if (index < 0) return -1; /* note: realloc has been done, so reload tables */ table = &vlc->table[table_index]; table[j][0] = index; //code i = k-1; } } return table_index; } /* Build VLC decoding tables suitable for use with get_vlc(). 'nb_bits' set thee decoding table size (2^nb_bits) entries. The bigger it is, the faster is the decoding. But it should not be too big to save memory and L1 cache. '9' is a good compromise. 'nb_codes' : number of vlcs codes 'bits' : table which gives the size (in bits) of each vlc code. 'codes' : table which gives the bit pattern of of each vlc code. 'symbols' : table which gives the values to be returned from get_vlc(). 'xxx_wrap' : give the number of bytes between each entry of the 'bits' or 'codes' tables. 'xxx_size' : gives the number of bytes of each entry of the 'bits' or 'codes' tables. 'wrap' and 'size' allows to use any memory configuration and types (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables. 'use_static' should be set to 1 for tables, which should be freed with av_free_static(), 0 if free_vlc() will be used. */ int 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) { VLCcode *buf; int i, j, ret; vlc->bits = nb_bits; if(flags & INIT_VLC_USE_NEW_STATIC){ if(vlc->table_size && vlc->table_size == vlc->table_allocated){ return 0; }else if(vlc->table_size){ abort(); // fatal error, we are called on a partially initialized table } }else { vlc->table = NULL; vlc->table_allocated = 0; vlc->table_size = 0; } #ifdef DEBUG_VLC av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes); #endif buf = av_malloc((nb_codes+1)*sizeof(VLCcode)); assert(symbols_size <= 2 || !symbols); j = 0; #define COPY(condition)\ for (i = 0; i < nb_codes; i++) {\ GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size);\ if (!(condition))\ continue;\ GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size);\ if (flags & INIT_VLC_LE)\ buf[j].code = bitswap_32(buf[j].code);\ else\ buf[j].code <<= 32 - buf[j].bits;\ if (symbols)\ GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size)\ else\ buf[j].symbol = i;\ j++;\ } COPY(buf[j].bits > nb_bits); // qsort is the slowest part of init_vlc, and could probably be improved or avoided qsort(buf, j, sizeof(VLCcode), compare_vlcspec); COPY(buf[j].bits && buf[j].bits <= nb_bits); nb_codes = j; ret = build_table(vlc, nb_bits, nb_codes, buf, flags); av_free(buf); if (ret < 0) { av_freep(&vlc->table); return -1; } if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated) av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated); return 0; } void free_vlc(VLC *vlc) { av_freep(&vlc->table); }