Add dynamic range notes to vp9_vector_var_c
Change-Id: If536ad31046ecd9e2ecd9c21f52f8192c8153ad7
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@ -155,6 +155,9 @@ int16_t vp9_int_pro_col_c(uint8_t const *ref, const int width) {
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return sum;
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}
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// ref: [0 - 510]
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// src: [0 - 510]
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// bwl: {2, 3, 4}
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int vp9_vector_var_c(int16_t const *ref, int16_t const *src,
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const int bwl) {
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int i;
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@ -162,11 +165,12 @@ int vp9_vector_var_c(int16_t const *ref, int16_t const *src,
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int sse = 0, mean = 0, var;
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for (i = 0; i < width; ++i) {
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int diff = ref[i] - src[i];
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mean += diff;
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sse += diff * diff;
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int diff = ref[i] - src[i]; // diff: dynamic range [-510, 510], 10 bits.
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mean += diff; // mean: dynamic range 16 bits.
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sse += diff * diff; // sse: dynamic range 26 bits.
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}
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// (mean * mean): dynamic range 31 bits.
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var = sse - ((mean * mean) >> (bwl + 2));
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return var;
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}
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