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Clarify dc[k]^ range

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Change-Id: If748958c8dd4f82bbef974aa4f40a4d0a758d10b
This commit is contained in:
Vincent Rabaud
2025-12-02 17:52:43 +01:00
parent 4c7aaa92e4
commit 507c372276
1 changed files with 5 additions and 1 deletions
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6
src/enc/analysis_enc.c
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@@ -269,8 +269,12 @@ static int FastMBAnalyze(VP8EncIterator* const it) {
VP8Mean16x4(it->yuv_in + Y_OFF_ENC + k * BPS, &dc[k]);
}
for (m = 0, m2 = 0, k = 0; k < 16; ++k) {
// dc[k] is at most 16 (for loop of 16)*(16*255) (max value in dc after
// Mean16x4, which uses two nested loops of 4). Squared as (16*16*255)^2, it
// fits in a uint32_t.
const uint32_t dc2 = dc[k] * dc[k];
m += dc[k];
m2 += (uint64_t)dc[k] * dc[k];
m2 += dc2;
}
if (kThreshold * m2 < m * m) {
VP8SetIntra16Mode(it, 0); // DC16