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author | Ganesh Ajjanagadde <gajjanag@gmail.com> | 2016-02-29 22:16:16 -0500 |
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committer | Rostislav Pehlivanov <atomnuker@gmail.com> | 2016-03-28 16:55:59 +0100 |
commit | 7c2576e15d3265ff8205923049fc371a3d229d06 (patch) | |
tree | 1c88cbfcb8e7530d89214c67abc96676bdb78760 /RELEASE | |
parent | 526c7b21865f8547fb425eeeb093f0765f1f9918 (diff) | |
download | ffmpeg-7c2576e15d3265ff8205923049fc371a3d229d06.tar.gz |
lavc/aacenc_utils: replace sqrtf(Q*sqrtf(Q)) by precomputed value
It makes no sense whatsoever to do this at each function call; we
already have a table for this.
Yields a 2x improvement in find_min_book (x86-64, Haswell+GCC):
ffmpeg -i sin.flac -acodec aac -y sin.aac
find_min_book
old
605 decicycles in find_min_book, 8388453 runs, 155 skips.9x
606 decicycles in find_min_book,16776912 runs, 304 skips.9x
607 decicycles in find_min_book,33553819 runs, 613 skips.2x
607 decicycles in find_min_book,67107668 runs, 1196 skips.3x
607 decicycles in find_min_book,134215360 runs, 2368 skips3x
new
359 decicycles in find_min_book, 8388552 runs, 56 skips.3x
360 decicycles in find_min_book,16777112 runs, 104 skips.1x
361 decicycles in find_min_book,33554218 runs, 214 skips.4x
361 decicycles in find_min_book,67108381 runs, 483 skips.5x
361 decicycles in find_min_book,134216725 runs, 1003 skips5x
and more importantly a non-negligible speedup (~ 8%) to overall AAC encoding:
old:
ffmpeg -i sin.flac -acodec aac -strict -2 -y sin_new.aac 6.82s user 0.03s system 104% cpu 6.565 total
new:
ffmpeg -i sin.flac -acodec aac -strict -2 -y sin_old.aac 6.24s user 0.03s system 104% cpu 5.993 total
This also improves accuracy of the expression by ~ 2 ulp in some cases.
Reviewed-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Reviewed-by: Rostislav Pehlivanov <atomnuker@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanag@gmail.com>
(cherry picked from commit bd9c58756a50b52e495b748d6ea6b0aafe397c25)
Diffstat (limited to 'RELEASE')
0 files changed, 0 insertions, 0 deletions