On 07.05.2019, at 01:33, Lynne <d...@lynne.ee> wrote: > May 6, 2019, 11:41 PM by barsn...@gmx.net: > >> On Mon, May 06, 2019 at 02:23:26 +0200, Lynne wrote: >> >>> This allowed for the exptabs to be computed just once on startup and >>> stored in a global array. >>> >> >> I have no real understanding of this, but: >> Would there be a desire for a static implementation as well, for those >> using "-enable-hardcoded-tables" (CONFIG_HARDCODED_TABLES)? Just >> wondering whether that's esoteric, optional, or really nice to have. >> >> Moritz >> > > Not really, its just nicer, saves 64 bytes per context and some time on > subsequent inits, > and might help with SIMD because more can be hardcoded into the assembly. > I don't think the hardcoded tables flag helps much nowadays, binary size > seems more > important to users shipping the libraries. Also it might improve precision > somewhat > for floats if the compiling machine has a different libc than the user's > machine, and the > sin/cos approximations used on the compiling machine's libc are worse.
It's a bit of a special case, but it also helps memory usage when many instances of FFmpeg run on the same machine. .rodata sections will be shared, whereas runtime-initialized sections will cause copy-on-write at initialization, and unless deduplication is possible and enabled (which has other costs) will use memory for each instance. It can also be swapped out or executed in-place for systems that support that, reducing memory usage of those tables to 0. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
