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Add dynamic range comment to hadamard_8x8()

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Add comment to assist SIMD optimization.

Change-Id: I300d5a848e6e9947e451de2a871a88940703fc9f
This commit is contained in:
Jingning Han 2015-06-12 10:38:45 -07:00
parent 254a4c033c
commit 4f52d49f1e
1 changed files with 8 additions and 3 deletions
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11
vp9/encoder/vp9_avg.c
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@ -29,6 +29,8 @@ unsigned int vp9_avg_4x4_c(const uint8_t *s, int p) {
return (sum + 8) >> 4;
}
// src_diff: first pass, 9 bit, dynamic range [-255, 255]
// second pass, 12 bit, dynamic range [-2040, 2040]
static void hadamard_col8(const int16_t *src_diff, int src_stride,
int16_t *coeff) {
int16_t b0 = src_diff[0 * src_stride] + src_diff[1 * src_stride];
@ -65,15 +67,18 @@ void vp9_hadamard_8x8_c(int16_t const *src_diff, int src_stride,
int16_t buffer[64];
int16_t *tmp_buf = &buffer[0];
for (idx = 0; idx < 8; ++idx) {
hadamard_col8(src_diff, src_stride, tmp_buf);
hadamard_col8(src_diff, src_stride, tmp_buf); // src_diff: 9 bit
// dynamic range [-255, 255]
tmp_buf += 8;
++src_diff;
}
tmp_buf = &buffer[0];
for (idx = 0; idx < 8; ++idx) {
hadamard_col8(tmp_buf, 8, coeff);
coeff += 8;
hadamard_col8(tmp_buf, 8, coeff); // tmp_buf: 12 bit
// dynamic range [-2040, 2040]
coeff += 8; // coeff: 15 bit
// dynamic range [-16320, 16320]
++tmp_buf;
}
}