[FFmpeg-soc] [soc]: r3046 - in aac: aac.c aac.h

Michael Niedermayer michaelni at gmx.at
Thu Aug 7 12:53:50 CEST 2008


On Thu, Aug 07, 2008 at 12:40:28PM +0200, Michael Niedermayer wrote:
> Hi
> 
> On Thu, Aug 07, 2008 at 08:50:05AM +0200, Reimar Doeffinger wrote:
> > On Wed, Aug 06, 2008 at 09:21:32PM -0400, Justin Ruggles wrote:
> > > superdump wrote:
> > > > Author: superdump
> > > > Date: Wed Aug  6 12:00:44 2008
> > > > New Revision: 3046
> > > > 
> > > > Log:
> > > > Use a simple LCG as recommended in libavutil/lfg.* rather than Mersenne Twister
> > > > as such noise is good enough (sounds the same to my ears on a 1 second sample)
> > > > and calculation is faster
> > > 
> > > Why not add that to libavutil as well?  I would like to use it for AC-3.
> > 
> > In that case though I think it would be nice if there was some additional information
> > on the particular numbers used, and also mentioning that the last bit is always alternating
> > for this kind of generator (so if possible, only the upper bits should be used).
> > Believing some random guy on the internet: http://random.mat.sbg.ac.at/~charly/server/node3.html
> > 2147001325*a+715136305
> > at least has some statistics, I could not find any for the current numbers on a quick search.
> 
> heres a quick comparission between the 2 generators:

heres the same, also with the next (poorly performing generator) from the
url as check if my tests catch poorly performing ones

*1664525+1013904223  *2147001325+715136305   (*452807053) & 0x7FFFFFFF;
test:0 tp: 0 0-16777208         0-16777208      0-67108830 
test:0 tp: 1 0-4194304          0-4194304       0-16777216 
test:0 tp: 2 0-1048576          0-1048576       0-4194304 
test:0 tp: 3 0-262144           0-262144        0-1048576 
test:0 tp: 4 0-65536            0-65536         0-262144 
test:0 tp: 5 0-32768            0-49152         0-65536 
test:0 tp: 6 0-12288            0-12288         0-32768 
test:0 tp: 7 0-6144             0-7168          0-8192 
test:0 tp: 8 0-3072             0-3584          0-6144 
test:0 tp: 9 384-1792           256-2240        0-2816 
test:0 tp:10 704-1408           656-1424        448-1728 
test:0 tp:11 880-1168           916-1140        704-1328 
test:0 tp:12 930-1122           971-1076        916-1152 
test:0 tp:13 905-1147           898-1165        971-1075 
test:0 tp:14 889-1167           889-1166        898-1150 
test:0 tp:15 891-1159           890-1164        0-263507 
test:1 tp: 0 0-33554432         0-33554432      0-67108864 
test:1 tp: 1 0-16777216         0-16777216      0-67108864 
test:1 tp: 2 0-8388608          0-8388608       0-33554432 
test:1 tp: 3 0-4194304          0-4194304       0-16777216 
test:1 tp: 4 0-2097152          0-2097152       0-8388608 
test:1 tp: 5 0-1048576          0-1048576       0-4194304 
test:1 tp: 6 0-524288           0-1048576       0-2097152 
test:1 tp: 7 0-262144           0-262144        0-1048576 
test:1 tp: 8 0-262144           0-262144        0-524288 
test:1 tp: 9 0-131072           0-131072        0-262144 
test:1 tp:10 0-65536            0-65536         0-262144 
test:1 tp:11 0-32768            0-49152         0-131072 
test:1 tp:12 0-24576            0-32768         0-65536 
test:1 tp:13 0-16384            0-24576         0-32768 
test:1 tp:14 0-10240            0-10240         0-24576 
test:1 tp:15 0-8192             0-7168          0-16384 
test:1 tp:16 0-5120             0-5120          0-10240 
test:1 tp:17 0-3584             0-4096          0-6144 
test:1 tp:18 0-2560             0-3456          0-4608 
test:1 tp:19 256-2112           192-2304        0-4096 
test:1 tp:20 416-1792           352-1856        0-2816 
test:1 tp:21 624-1552           576-1552        128-2176 
test:1 tp:22 744-1368           688-1376        416-1760 
test:1 tp:23 796-1276           780-1244        640-1424 
test:1 tp:24 822-1232           866-1202        736-1352 
test:1 tp:25 889-1176           911-1137        804-1244 
test:1 tp:26 864-1173           902-1141        856-1174 
test:1 tp:27 891-1170           894-1155        923-1115 
test:1 tp:28 891-1156           897-1155        899-1155 
test:1 tp:29 898-1181           883-1160        902-1161 
test:1 tp:30 897-1167           897-1178        876-1173 
test:1 tp:31 900-1177           896-1164        0-67108864 
test:2 tp: 0 1024-1024          1024-1024       0-4096 
test:2 tp: 1 1024-1024          1024-1024       0-2048 
test:2 tp: 2 1024-1024          1024-1024       1024-1024 
test:2 tp: 3 1024-1024          1024-1024       1024-1024 
test:2 tp: 4 1024-1024          1024-1024       1024-1024 
test:2 tp: 5 1024-1024          1024-1024       1024-1024 
test:2 tp: 6 1024-1024          1024-1024       1024-1024 
test:2 tp: 7 1024-1024          1024-1024       1024-1024 
test:2 tp: 8 1024-1024          1024-1024       1024-1024 
test:2 tp: 9 1024-1024          1024-1024       1024-1024 
test:2 tp:10 1024-1024          1024-1024       1024-1024 
test:2 tp:11 906-1142           928-1120        1024-1024 
test:2 tp:12 894-1135           891-1142        1024-1024 
test:2 tp:13 900-1170           899-1157        934-1114 
test:2 tp:14 881-1159           900-1165        910-1139 
test:2 tp:15 897-1153           893-1179        900-1163 
test:2 tp:16 877-1168           888-1171        0-2236 
test:3 tp: 0 0-33554425         0-33554425      0-67108849 
test:3 tp: 1 0-16777213         0-16777213      0-67108849 
test:3 tp: 2 0-8388607          0-8388607       0-33554425 
test:3 tp: 3 0-4194304          0-4194304       0-16777213 
test:3 tp: 4 0-2097152          0-2097152       0-8388607 
test:3 tp: 5 0-1048576          0-1048576       0-4194304 
test:3 tp: 6 0-524288           0-524288        0-2097152 
test:3 tp: 7 0-262144           0-262144        0-1048576 
test:3 tp: 8 0-131072           0-131072        0-524288 
test:3 tp: 9 0-131072           0-131072        0-262144 
test:3 tp:10 0-65536            0-65536         0-131072 
test:3 tp:11 0-32768            0-32768         0-131072 
test:3 tp:12 0-24576            0-24576         0-65536 
test:3 tp:13 0-16384            0-20480         0-49152 
test:3 tp:14 0-12288            0-10240         0-24576 
test:3 tp:15 0-9216             0-6144          0-12288 
test:3 tp:16 0-4608             0-4608          0-10240 
test:3 tp:17 0-3328             0-3840          0-7168 
test:3 tp:18 0-2560             0-2560          0-4608 
test:3 tp:19 192-2240           128-2176        0-3840 
test:3 tp:20 384-1888           352-1792        0-2432 
test:3 tp:21 560-1584           624-1504        192-2176 
test:3 tp:22 656-1400           696-1336        448-1824 
test:3 tp:23 756-1296           828-1252        512-1632 
test:3 tp:24 806-1272           888-1178        632-1432 
test:3 tp:25 934-1134           929-1124        708-1316 
test:3 tp:26 914-1138           914-1133        786-1274 
test:3 tp:27 897-1152           906-1159        920-1128 
test:3 tp:28 883-1175           902-1160        891-1156 
test:3 tp:29 864-1160           897-1160        892-1171 
test:3 tp:30 898-1200           895-1157        894-1164 
test:3 tp:31 884-1196           890-1155        0-67108850 

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The educated differ from the uneducated as much as the living from the
dead. -- Aristotle 
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