* For licencing details see COPYING.LIB.
*/
-/**
- * \file bitstream.c Bitstream API.
- */
+/** \file bitstream.c Bitstream API for the wma decoder. */
-#include <stdlib.h>
-#include <inttypes.h>
-#include <stdio.h>
-#include <string.h>
#include <regex.h>
#include "para.h"
#include "wma.h"
#include "bitstream.h"
-#define GET_DATA(v, table, i, wrap, size) \
+/** Read an 8, 16, or 32 bit entity from a VLC table. */
+#define GET_DATA(v, table, i, size) \
{\
- const uint8_t *ptr = (const uint8_t *)table + i * wrap; \
+ const uint8_t *ptr = (const uint8_t *)table + i * size; \
switch (size) { \
case 1: \
v = *(const uint8_t *)ptr; \
}
static int build_table(struct vlc *vlc, int table_nb_bits, int nb_codes,
- const void *bits, const void *codes, int codes_wrap,
- int codes_size, uint32_t code_prefix, int n_prefix)
+ const void *bits, const void *codes, int codes_size,
+ uint32_t code_prefix, int n_prefix)
{
- int ret, i, j, k, n, table_size, table_index, nb, n1, idx, code_prefix2,
- symbol;
+ int i, j, k, n, table_size, table_index, nb, n1, idx;
uint32_t code;
VLC_TYPE(*table)[2];
table = &vlc->table[table_index];
for (i = 0; i < table_size; i++) {
- table[i][1] = 0; //bits
- table[i][0] = -1; //codes
+ table[i][1] = 0; /* bits */
+ table[i][0] = -1; /* codes */
}
- /* first pass: map codes and compute auxillary table sizes */
+ /* map codes and compute auxiliary table sizes */
for (i = 0; i < nb_codes; i++) {
- GET_DATA(n, bits, i, 1, 1);
- GET_DATA(code, codes, i, codes_wrap, codes_size);
+ GET_DATA(n, bits, i, 1);
/* we accept tables with holes */
+ n -= n_prefix;
if (n <= 0)
continue;
- symbol = i;
+ GET_DATA(code, codes, i, codes_size);
/* if code matches the prefix, it is in the table */
- n -= n_prefix;
- code_prefix2 = code >> n;
- if (n > 0 && code_prefix2 == 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)
- return -E_BAD_CODES;
- table[j][1] = n; //bits
- table[j][0] = symbol;
- 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
+ if ((code >> n) != code_prefix)
+ continue;
+ 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++) {
+ assert(table[j][1] == 0); /* incorrect code */
+ table[j][1] = n; /* bits */
+ table[j][0] = i;
+ 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 */
+ /* fill auxiliary tables recursively */
for (i = 0; i < table_size; i++) {
- n = table[i][1]; //bits
+ n = table[i][1]; /* bits */
if (n < 0) {
n = -n;
if (n > table_nb_bits) {
n = table_nb_bits;
- table[i][1] = -n; //bits
+ table[i][1] = -n; /* bits */
}
- ret = build_table(vlc, n, nb_codes,
- bits, codes, codes_wrap, codes_size,
- (code_prefix << table_nb_bits) | i,
+ idx = build_table(vlc, n, nb_codes, bits, codes,
+ codes_size, (code_prefix << table_nb_bits) | i,
n_prefix + table_nb_bits);
- if (ret < 0)
- return ret;
- idx = ret;
- /* note: realloc has been done, so reload tables */
+ /* vlc->table might have changed */
table = &vlc->table[table_index];
- table[i][0] = idx; //code
+ table[i][0] = idx; /* code */
}
}
return table_index;
/**
* Build VLC decoding tables suitable for use with get_vlc().
*
- * \param nb_bits Set the 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.
- *
- * \param nb_codes Number of vlcs codes.
- *
- * \param bits Table which gives the size (in bits) of each
- * vlc code.
+ * \param vlc The structure to be initialized.
+ * \param nb_bits Set the decoding table size (2^nb_bits) entries.
+ * \param nb_codes Number of vlc codes.
+ * \param bits Table which gives the size (in bits) of each vlc code.
+ * \param codes Table which gives the bit pattern of of each vlc code.
+ * \param codes_size The number of bytes of each entry of the \a codes tables.
*
- * \param codes Table which gives the bit pattern of of each
- * vlc code.
- *
- * \param codes_wrap The number of bytes between each entry of the
- * 'codes' tables.
- *
- * \param codes_size The number of bytes of each entry of the
- * 'codes' tables.
+ * The bigger \a nb_bits is, the faster is the decoding. But it should not be
+ * too big to save memory and L1 cache. '9' is a good compromise.
*
* The wrap and size parameters allow to use any memory configuration and
* types (byte/word/long) to store the bits and codes tables.
*/
-int init_vlc(struct vlc *vlc, int nb_bits, int nb_codes,
- const void *bits, const void *codes, int codes_wrap,
- int codes_size)
+void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
+ const void *codes, int codes_size)
{
- int ret;
-
- PARA_INFO_LOG("nb_codes=%d\n", nb_codes);
+ PARA_INFO_LOG("nb_codes: %d\n", nb_codes);
vlc->bits = nb_bits;
vlc->table = NULL;
vlc->table_allocated = 0;
vlc->table_size = 0;
- ret = build_table(vlc, nb_bits, nb_codes, bits,
- codes, codes_wrap, codes_size, 0, 0);
- if (ret < 0)
- freep(&vlc->table);
- return ret;
+ build_table(vlc, nb_bits, nb_codes, bits, codes, codes_size, 0, 0);
}
+/**
+ * Deallocate all resources of a VLC table.
+ *
+ * \param vlc Pointer to an initialized vlc structure.
+ *
+ * The table given by \a vlc must have been initialized earlier via \ref
+ * init_vlc().
+ */
void free_vlc(struct vlc *vlc)
{
freep(&vlc->table);
}
+
+/**
+ * Parse a vlc code.
+ *
+ * \param gbc The getbit context structure.
+ * \param table The vlc tables to use.
+ * \param bits The number of bits which will be read at once.
+ * \param max_depth The number of times \a bits bits must be read to completely
+ * read the longest vlc code = (max_vlc_length + bits - 1) / bits.
+ *
+ * The \a bits parameter must be identical to the \a nb_bits value supplied to
+ * \ref init_vlc().
+ *
+ * \return The vlc code.
+ */
+int get_vlc(struct getbit_context *gbc, VLC_TYPE(*table)[2], int bits,
+ int max_depth)
+{
+ int n, idx, nb_bits, code;
+
+ idx = show_bits(gbc, bits);
+ code = table[idx][0];
+ n = table[idx][1];
+ if (max_depth > 1 && n < 0) {
+ skip_bits(gbc, bits);
+ nb_bits = -n;
+ idx = show_bits(gbc, nb_bits) + code;
+ code = table[idx][0];
+ n = table[idx][1];
+ if (max_depth > 2 && n < 0) {
+ skip_bits(gbc, nb_bits);
+ nb_bits = -n;
+ idx = show_bits(gbc, nb_bits) + code;
+ code = table[idx][0];
+ n = table[idx][1];
+ }
+ }
+ skip_bits(gbc, n);
+ return code >= 0? code : -E_VLC;
+}
projects / paraslash.git / blobdiff