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inline VP8LFastLog2() and VP8LFastSLog2 for small values

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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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16
src/dsp/lossless.h
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@ -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) {