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avcodec/vlc: Add documentation for ff_init_vlc_sparse()

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Mostly taken from the documentation for ff_init_vlc_from_lengths();
also remove the documentation in vlc.c.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2023-09-08 14:10:10 +02:00
parent a84fe06112
commit 7b98a1875d
2 changed files with 29 additions and 23 deletions
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23
libavcodec/vlc.c
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@ -247,29 +247,6 @@ static int vlc_common_end(VLC *vlc, int nb_bits, int nb_codes, VLCcode *codes,
return 0;
}
/* Build VLC decoding tables suitable for use with get_vlc().
'nb_bits' sets 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.
'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. Currently 1,2 and 4 are supported.
'wrap' and 'size' make it possible to use any memory configuration and types
(byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
*/
int ff_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,

29
libavcodec/vlc.h
View File

@ -62,6 +62,35 @@ typedef struct RL_VLC_ELEM {
codes, codes_wrap, codes_size, \
NULL, 0, 0, flags)
/**
* Build VLC decoding tables suitable for use with get_vlc2().
*
* @param[in,out] vlc The VLC to be initialized; table and table_allocated
* must have been set when initializing a static VLC,
* otherwise this will be treated as uninitialized.
* @param[in] nb_bits The number of bits to use for the VLC table;
* higher values take up more memory and cache, but
* allow to read codes with fewer reads.
* Corresponds to the `bits` parameter of get_vlc2().
* @param[in] nb_codes The number of provided bits, codes and (if supplied)
* symbol entries.
* @param[in] bits The lengths (in bits) of the codes. Entries > 0
* correspond to valid codes; entries == 0 will be skipped.
* @param[in] bits_wrap Stride (in bytes) of the bits table.
* @param[in] codes_size Size of the bits. 1, 2 and 4 are supported.
* @param[in] codes Table which gives the bit pattern of of each vlc code.
* @param[in] codes_wrap Stride (in bytes) of the codes table.
* @param[in] codes_size Size of the codes. 1, 2 and 4 are supported.
* @param[in] symbols The symbols, i.e. what is returned from get_vlc2()
* when the corresponding code is encountered.
* May be NULL, then 0, 1, 2, 3, 4,... will be used.
* @param[in] symbols_wrap Stride (in bytes) of the symbols table.
* @param[in] symbols_size Size of the symbols. 1 and 2 are supported.
* @param[in] flags A combination of the INIT_VLC_* flags.
*
* 'wrap' and 'size' make it possible to use any memory configuration and types
* (byte/word/int) to store the 'bits', 'codes', and 'symbols' tables.
*/
int ff_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,