ref: 4f52d49f1e21dde76640f22c5932ce6ec08cb534
parent: 254a4c033c7bcec3b6b0fbbb86301d18491ebc26
author: Jingning Han <[email protected]>
date: Fri Jun 12 06:38:45 EDT 2015
Add dynamic range comment to hadamard_8x8() Add comment to assist SIMD optimization. Change-Id: I300d5a848e6e9947e451de2a871a88940703fc9f
--- a/vp9/encoder/vp9_avg.c
+++ b/vp9/encoder/vp9_avg.c
@@ -29,6 +29,8 @@
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];
@@ -65,7 +67,8 @@
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;
}
@@ -72,8 +75,10 @@
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;
}
}