ffmpeg | branch: master | Ganesh Ajjanagadde <gajjanaga...@gmail.com> | Wed Dec 30 20:02:11 2015 -0800| [43624a669b706168989a3b1ac608943f8cb208d1] | committer: Ganesh Ajjanagadde
lavc/pcm_tablegen: slight speedup of table generation This gets rid of some branches to speed up table generation slightly (impact higher on mulaw than alaw). Tables are identical to before, tested with FATE. Sample benchmark (Haswell, GNU/Linux+gcc): old: 313494 decicycles in build_alaw_table, 4094 runs, 2 skips 315959 decicycles in build_alaw_table, 8190 runs, 2 skips 323599 decicycles in build_ulaw_table, 4095 runs, 1 skips 318849 decicycles in build_ulaw_table, 8188 runs, 4 skips new: 261902 decicycles in build_alaw_table, 4096 runs, 0 skips 266519 decicycles in build_alaw_table, 8192 runs, 0 skips 209657 decicycles in build_ulaw_table, 4096 runs, 0 skips 232656 decicycles in build_ulaw_table, 8192 runs, 0 skips Reviewed-by: Michael Niedermayer <mich...@niedermayer.cc> Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com> > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=43624a669b706168989a3b1ac608943f8cb208d1 --- libavcodec/pcm_tablegen.h | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/libavcodec/pcm_tablegen.h b/libavcodec/pcm_tablegen.h index 1387210..7269977 100644 --- a/libavcodec/pcm_tablegen.h +++ b/libavcodec/pcm_tablegen.h @@ -87,21 +87,21 @@ static av_cold void build_xlaw_table(uint8_t *linear_to_xlaw, { int i, j, v, v1, v2; - j = 0; - for(i=0;i<128;i++) { - if (i != 127) { - v1 = xlaw2linear(i ^ mask); - v2 = xlaw2linear((i + 1) ^ mask); - v = (v1 + v2 + 4) >> 3; - } else { - v = 8192; - } - for(;j<v;j++) { + j = 1; + linear_to_xlaw[8192] = mask; + for(i=0;i<127;i++) { + v1 = xlaw2linear(i ^ mask); + v2 = xlaw2linear((i + 1) ^ mask); + v = (v1 + v2 + 4) >> 3; + for(;j<v;j+=1) { + linear_to_xlaw[8192 - j] = (i ^ (mask ^ 0x80)); linear_to_xlaw[8192 + j] = (i ^ mask); - if (j > 0) - linear_to_xlaw[8192 - j] = (i ^ (mask ^ 0x80)); } } + for(;j<8192;j++) { + linear_to_xlaw[8192 - j] = (127 ^ (mask ^ 0x80)); + linear_to_xlaw[8192 + j] = (127 ^ mask); + } linear_to_xlaw[0] = linear_to_xlaw[1]; } _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog
