Commit 4644a7d0 authored by Nathan E. Egge's avatar Nathan E. Egge Committed by Tim Terriberry

daala_tx: New flattened 4-point Type-IV DST.

This change slightly improves the 16-point DCT round trip accuracy due
 to changes in the rounding.

subset-1:

new_dst2@2017-12-04T01:59:57.412Z -> new_dst4@2017-12-04T06:31:41.096Z

  PSNR | PSNR Cb | PSNR Cr | PSNR HVS |   SSIM | MS SSIM | CIEDE 2000
0.0078 | -0.0001 |  0.0198 |   0.0432 | 0.0408 |  0.0502 |    -0.0057

Change-Id: I75783ace97834af89e70c9ce3002c6f09176e343
parent ef525df6
......@@ -415,12 +415,12 @@
q3 -= q2; \
q0 += OD_RSHIFT1(q1); \
q1 -= q0; \
t_ = (q2 - q1 + 1) >> 1; \
t_ = (q1 + q2 + 1) >> 1; \
/* 11585/8192 ~= 2*Sin[Pi/4] ~= 1.4142135623730951 */ \
q2 = (11585*q1 + 4096) >> 13; \
q1 = (11585*q2 + 4096) >> 13; \
/* 11585/8192 ~= 2*Cos[Pi/4] ~= 1.4142135623730951 */ \
q1 = (11585*t_ + 4096) >> 13; \
q2 += q1; \
q2 = (11585*t_ + 4096) >> 13; \
q1 -= q2; \
} \
while (0)
......
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