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inline VP8LFastLog2() and VP8LFastSLog2 for small values

Browse Source 
larger values are still dealt with in the .cc

~5% faster encoding
Output size is slightly different (variably), because of
different floating-point calculation ordering.

Change-Id: I6ede18b09c753997cf78aa1199a807d9ddb5d4b4
This commit is contained in:
skal 2013-02-25 22:46:52 +01:00
parent 5cf7792e40
commit b7eaa85d6a
2 changed files with 100 additions and 10 deletions
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94
src/dsp/lossless.c
View File

@ -35,8 +35,7 @@ extern "C" {
// lookup table for small values of log2(int)
#define APPROX_LOG_MAX 4096
#define LOG_2_RECIPROCAL 1.44269504088896338700465094007086
#define LOG_LOOKUP_IDX_MAX 256
static const float kLog2Table[LOG_LOOKUP_IDX_MAX] = {
const float kLog2Table[LOG_LOOKUP_IDX_MAX] = {
0.0000000000000000f, 0.0000000000000000f,
1.0000000000000000f, 1.5849625007211560f,
2.0000000000000000f, 2.3219280948873621f,
@ -167,16 +166,97 @@ static const float kLog2Table[LOG_LOOKUP_IDX_MAX] = {
7.9886846867721654f, 7.9943534368588577f
};
float VP8LFastLog2(int v) {
if (v < LOG_LOOKUP_IDX_MAX) {
return kLog2Table[v];
} else if (v < APPROX_LOG_MAX) {
const float kSLog2Table[LOG_LOOKUP_IDX_MAX] = {
0.00000000f, 0.00000000f, 2.00000000f, 4.75488750f,
8.00000000f, 11.60964047f, 15.50977500f, 19.65148445f,
24.00000000f, 28.52932501f, 33.21928095f, 38.05374781f,
43.01955001f, 48.10571634f, 53.30296891f, 58.60335893f,
64.00000000f, 69.48686830f, 75.05865003f, 80.71062276f,
86.43856190f, 92.23866588f, 98.10749561f, 104.04192499f,
110.03910002f, 116.09640474f, 122.21143267f, 128.38196256f,
134.60593782f, 140.88144886f, 147.20671787f, 153.58008562f,
160.00000000f, 166.46500594f, 172.97373660f, 179.52490559f,
186.11730005f, 192.74977453f, 199.42124551f, 206.13068654f,
212.87712380f, 219.65963219f, 226.47733176f, 233.32938445f,
240.21499122f, 247.13338933f, 254.08384998f, 261.06567603f,
268.07820003f, 275.12078236f, 282.19280949f, 289.29369244f,
296.42286534f, 303.57978409f, 310.76392512f, 317.97478424f,
325.21187564f, 332.47473081f, 339.76289772f, 347.07593991f,
354.41343574f, 361.77497759f, 369.16017124f, 376.56863518f,
384.00000000f, 391.45390785f, 398.93001188f, 406.42797576f,
413.94747321f, 421.48818752f, 429.04981119f, 436.63204548f,
444.23460010f, 451.85719280f, 459.49954906f, 467.16140179f,
474.84249102f, 482.54256363f, 490.26137307f, 497.99867911f,
505.75424759f, 513.52785023f, 521.31926438f, 529.12827280f,
536.95466351f, 544.79822957f, 552.65876890f, 560.53608414f,
568.42998244f, 576.34027536f, 584.26677867f, 592.20931226f,
600.16769996f, 608.14176943f, 616.13135206f, 624.13628279f,
632.15640007f, 640.19154569f, 648.24156472f, 656.30630539f,
664.38561898f, 672.47935976f, 680.58738488f, 688.70955430f,
696.84573069f, 704.99577935f, 713.15956818f, 721.33696754f,
729.52785023f, 737.73209140f, 745.94956849f, 754.18016116f,
762.42375127f, 770.68022275f, 778.94946161f, 787.23135586f,
795.52579543f, 803.83267219f, 812.15187982f, 820.48331383f,
828.82687147f, 837.18245171f, 845.54995518f, 853.92928416f,
862.32034249f, 870.72303558f, 879.13727036f, 887.56295522f,
896.00000000f, 904.44831595f, 912.90781569f, 921.37841320f,
929.86002376f, 938.35256392f, 946.85595152f, 955.37010560f,
963.89494641f, 972.43039537f, 980.97637504f, 989.53280911f,
998.09962237f, 1006.67674069f, 1015.26409097f, 1023.86160116f,
1032.46920021f, 1041.08681805f, 1049.71438560f, 1058.35183469f,
1066.99909811f, 1075.65610955f, 1084.32280357f, 1092.99911564f,
1101.68498204f, 1110.38033993f, 1119.08512727f, 1127.79928282f,
1136.52274614f, 1145.25545758f, 1153.99735821f, 1162.74838989f,
1171.50849518f, 1180.27761738f, 1189.05570047f, 1197.84268914f,
1206.63852876f, 1215.44316535f, 1224.25654560f, 1233.07861684f,
1241.90932703f, 1250.74862473f, 1259.59645914f, 1268.45278005f,
1277.31753781f, 1286.19068338f, 1295.07216828f, 1303.96194457f,
1312.85996488f, 1321.76618236f, 1330.68055071f, 1339.60302413f,
1348.53355734f, 1357.47210556f, 1366.41862452f, 1375.37307041f,
1384.33539991f, 1393.30557020f, 1402.28353887f, 1411.26926400f,
1420.26270412f, 1429.26381818f, 1438.27256558f, 1447.28890615f,
1456.31280014f, 1465.34420819f, 1474.38309138f, 1483.42941118f,
1492.48312945f, 1501.54420843f, 1510.61261078f, 1519.68829949f,
1528.77123795f, 1537.86138993f, 1546.95871952f, 1556.06319119f,
1565.17476976f, 1574.29342040f, 1583.41910860f, 1592.55180020f,
1601.69146137f, 1610.83805860f, 1619.99155871f, 1629.15192882f,
1638.31913637f, 1647.49314911f, 1656.67393509f, 1665.86146266f,
1675.05570047f, 1684.25661744f, 1693.46418280f, 1702.67836605f,
1711.89913698f, 1721.12646563f, 1730.36032233f, 1739.60067768f,
1748.84750254f, 1758.10076802f, 1767.36044551f, 1776.62650662f,
1785.89892323f, 1795.17766747f, 1804.46271172f, 1813.75402857f,
1823.05159087f, 1832.35537170f, 1841.66534438f, 1850.98148244f,
1860.30375965f, 1869.63214999f, 1878.96662767f, 1888.30716711f,
1897.65374295f, 1907.00633003f, 1916.36490342f, 1925.72943838f,
1935.09991037f, 1944.47629506f, 1953.85856831f, 1963.24670620f,
1972.64068498f, 1982.04048108f, 1991.44607117f, 2000.85743204f,
2010.27454072f, 2019.69737440f, 2029.12591044f, 2038.56012640f
};
float VP8LFastSLog2Slow(int v) {
assert(v >= LOG_LOOKUP_IDX_MAX);
if (v < APPROX_LOG_MAX) {
int log_cnt = 0;
const float v_f = (float)v;
while (v >= LOG_LOOKUP_IDX_MAX) {
++log_cnt;
v = v >> 1;
}
return v_f * (kLog2Table[v] + log_cnt);
} else {
return (float)(LOG_2_RECIPROCAL * v * log((double)v));
}
}
float VP8LFastLog2Slow(int v) {
assert(v >= LOG_LOOKUP_IDX_MAX);
if (v < APPROX_LOG_MAX) {
int log_cnt = 0;
while (v >= LOG_LOOKUP_IDX_MAX) {
++log_cnt;
v = v >> 1;
}
return kLog2Table[v] + (float)log_cnt;
return kLog2Table[v] + log_cnt;
} else {
return (float)(LOG_2_RECIPROCAL * log((double)v));
}

16
src/dsp/lossless.h
View File

@ -59,10 +59,20 @@ static WEBP_INLINE uint32_t VP8LSubSampleSize(uint32_t size,
return (size + (1 << sampling_bits) - 1) >> sampling_bits;
}
// Faster logarithm for integers, with the property of log2(0) == 0.
float VP8LFastLog2(int v);
// Faster logarithm for integers. Small values use a look-up table.
#define LOG_LOOKUP_IDX_MAX 256
extern const float kLog2Table[LOG_LOOKUP_IDX_MAX];
extern const float kSLog2Table[LOG_LOOKUP_IDX_MAX];
extern float VP8LFastLog2Slow(int v);
extern float VP8LFastSLog2Slow(int v);
static WEBP_INLINE float VP8LFastLog2(int v) {
return (v < LOG_LOOKUP_IDX_MAX) ? kLog2Table[v] : VP8LFastLog2Slow(v);
}
// Fast calculation of v * log2(v) for integer input.
static WEBP_INLINE float VP8LFastSLog2(int v) { return VP8LFastLog2(v) * v; }
static WEBP_INLINE float VP8LFastSLog2(int v) {
return (v < LOG_LOOKUP_IDX_MAX) ? kSLog2Table[v] : VP8LFastSLog2Slow(v);
}
// In-place difference of each component with mod 256.
static WEBP_INLINE uint32_t VP8LSubPixels(uint32_t a, uint32_t b) {