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authorAndreas Rheinhardt <andreas.rheinhardt@outlook.com>2022-09-06 02:12:14 +0200
committerAndreas Rheinhardt <andreas.rheinhardt@outlook.com>2022-09-16 18:07:29 +0200
commit97610e856a4498c725e51497e287f31b367e5dd7 (patch)
tree91fffea367258fd03c24572ba0e6fb819cac92dc /libavcodec/cbs_mpeg2.c
parent2339f63eac90a7a3b25f2d5ee5749dbc46563684 (diff)
downloadffmpeg-97610e856a4498c725e51497e287f31b367e5dd7.tar.gz
avcodec/dcahuff: Combine tables, use ff_init_vlc_from_lengths()
Up until now, initializing the dca VLC tables uses ff_init_vlc_sparse() with length tables of type uint8_t and code tables of type uint16_t (except for the LBR tables, which uses length and symbols of type uint8_t; these tables are interleaved). In case of the quant index codebooks these arrays were accessed via tables of pointers to the individual tables. This commit changes this: First, we switch to ff_init_vlc_from_lengths() to replace the uint16_t code tables by uint8_t symbol tables (this necessitates ordering the tables from left-to-right in the tree first). These symbol tables are interleaved with the length tables. Furthermore, these tables are combined in order to remove the table of pointers to individual tables, thereby avoiding relocations (for x64 elf systems this amounts to 96*24B = 2304B saved in .rela.dyn) and saving 1280B from .data.rel.ro (for 64bit systems). Meanwhile the savings in .rodata amount to 2709 + 2 * 334 = 3377B. Due to padding the actual savings are higher: The ELF x64 ABI requires objects >= 16B to be padded to 16B and lots of the tables have 2^n + 1 elements of these were from replacing uint16_t codes with uint8_t symbols; the rest was due to the fact that combining the tables eliminated padding (the ELF x64 ABI requires objects >= 16B to be padded to 16B and lots of the tables have 2^n + 1 elements)). Taking this into account gives savings of 4548B. (GCC by default uses an even higher alignment (controlled by -malign-data); for it the savings are 5748B.) These changes also necessitated to modify the init code for the encoder tables. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Diffstat (limited to 'libavcodec/cbs_mpeg2.c')
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