/** \file bitstream.h Bitstream structures and inline functions. */
-#define AV_RB32(x) ((((const uint8_t*)(x))[0] << 24) | \
- (((const uint8_t*)(x))[1] << 16) | \
- (((const uint8_t*)(x))[2] << 8) | \
- ((const uint8_t*)(x))[3])
-
/** Structure for bistream I/O. */
struct getbit_context {
/* Start of the internal buffer. */
#define VLC_TYPE int16_t
+/** A variable length code table. */
struct vlc {
+ /** Number of bits of the table. */
int bits;
- VLC_TYPE(*table)[2]; ///< code, bits
- int table_size, table_allocated;
+ /** The code and the bits table. */
+ VLC_TYPE(*table)[2];
+ /** The size of the table. */
+ int table_size;
+ /** Amount of memory allocated so far. */
+ int table_allocated;
};
static inline uint32_t show_bits(struct getbit_context *gbc, int num)
{
int idx = gbc->index;
- uint32_t x = AV_RB32(gbc->buffer + (idx >> 3)) << (idx & 7);
- return x >> (32 - num);
+ const uint8_t *p = gbc->buffer + (idx >> 3);
+ uint32_t x = ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3]);
+ return (x << (idx & 7)) >> (32 - num);
}
static inline int get_bits_count(struct getbit_context *gbc)
}
/* This is rather hot, we can do better than get_bits(gbc, 1). */
-static inline unsigned int get_bits1(struct getbit_context *gbc)
+static inline unsigned int get_bit(struct getbit_context *gbc)
{
int idx = gbc->index++;
uint8_t tmp = gbc->buffer[idx >> 3], mask = (1 << (7 - (idx & 7)));
/**
* Initialize a getbit_context structure.
*
- * \param buffer The bitstream buffer. It must be FF_INPUT_BUFFER_PADDING_SIZE
- * bytes larger then the actual read bits * because some optimized bitstream
- * readers read 32 or 64 bit at once and could read over the end.
+ * \param buffer The bitstream buffer. It must be 4 bytes larger then the
+ * actual read bits because the bitstream reader might read 32 bits at once and
+ * could read over the end.
*
* \param bit_size The size of the buffer in bytes.
*/
void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
const void *codes, int codes_size);
-
void free_vlc(struct vlc *vlc);
+int get_vlc(struct getbit_context *gbc, VLC_TYPE(*table)[2], int bits,
+ int max_depth);
-/**
- * Parse a vlc code.
- *
- * \param bits The number of bits which will be read at once, must be
- * identical to nb_bits in init_vlc()
- *
- * \param max_depth The number of times bits bits must be read to completely
- * read the longest vlc code = (max_vlc_length + bits - 1) / bits.
- */
-static inline 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;
-}