diff options
Diffstat (limited to 'apps/codecs/libwma/common.c')
| -rw-r--r-- | apps/codecs/libwma/common.c | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/apps/codecs/libwma/common.c b/apps/codecs/libwma/common.c index 619ce47197..b4577a4c74 100644 --- a/apps/codecs/libwma/common.c +++ b/apps/codecs/libwma/common.c @@ -105,3 +105,164 @@ int check_marker(GetBitContext *s, const char *msg) return bit; } +/* 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 index; + index = vlc->table_size; + vlc->table_size += size; + if (vlc->table_size > vlc->table_allocated) { + vlc->table_allocated += (1 << vlc->bits); + if (!vlc->table) + return -1; + } + return index; +} + +static int build_table(VLC *vlc, int table_nb_bits, + int nb_codes, + const void *bits, int bits_wrap, int bits_size, + const void *codes, int codes_wrap, int codes_size, + uint32_t code_prefix, int n_prefix) +{ + int i, j, k, n, table_size, table_index, nb, n1, index; + uint32_t code; + VLC_TYPE (*table)[2]; + + table_size = 1 << table_nb_bits; + table_index = alloc_table(vlc, table_size); + 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++) + { + GET_DATA(n, bits, i, bits_wrap, bits_size); + GET_DATA(code, codes, i, codes_wrap, codes_size); + /* we accept tables with holes */ + if (n <= 0) + continue; + /* if code matches the prefix, it is in the table */ + n -= n_prefix; + if (n > 0 && (code >> n) == code_prefix) + { + if (n <= table_nb_bits) + { + /* no need to add another table */ + j = (code << (table_nb_bits - n)) & (table_size - 1); + nb = 1 << (table_nb_bits - n); + for(k=0;k<nb;k++) + { + if (table[j][1] /*bits*/ != 0) + { + // PJJ exit(-1); + } + table[j][1] = n; //bits + table[j][0] = i; //code + j++; + } + } + else + { + n -= table_nb_bits; + j = (code >> n) & ((1 << table_nb_bits) - 1); + /* compute table size */ + n1 = -table[j][1]; //bits + if (n > n1) + n1 = n; + table[j][1] = -n1; //bits + } + } + } + + /* second pass : fill auxillary tables recursively */ + for(i=0;i<table_size;i++) + { + n = table[i][1]; //bits + if (n < 0) + { + n = -n; + if (n > table_nb_bits) + { + n = table_nb_bits; + table[i][1] = -n; //bits + } + index = build_table(vlc, n, nb_codes, + bits, bits_wrap, bits_size, + codes, codes_wrap, codes_size, + (code_prefix << table_nb_bits) | i, + n_prefix + table_nb_bits); + if (index < 0) + return -1; + /* note: realloc has been done, so reload tables */ + table = &vlc->table[table_index]; + table[i][0] = index; //code + } + } + 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. + + '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' and 'codes' tables. +*/ +int init_vlc(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) +{ + vlc->bits = nb_bits; + vlc->table_size = 0; + + if (build_table(vlc, nb_bits, nb_codes, + bits, bits_wrap, bits_size, + codes, codes_wrap, codes_size, + 0, 0) < 0) + { + + return -1; + } + return 0; +} |