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| author | Ching-Kang Yen <chingkang@chromium.org> | 2020-10-06 23:27:21 +0800 |
|---|---|---|
| committer | Commit Bot <commit-bot@chromium.org> | 2020-11-06 06:02:48 +0000 |
| commit | 4d8de47ad47141bbc070725a0a4359a126bbb962 (patch) | |
| tree | 934b87c5786d3a21859964067a86b4a9adc6f2b1 /common/body_detection.c | |
| parent | 8f91458a1b888bb75f6f4d3ffe4d0de1a221a589 (diff) | |
| download | chrome-ec-4d8de47ad47141bbc070725a0a4359a126bbb962.tar.gz | |
common: body_detection: modify variance updating formula
Modify the variance formula to speed up body detection.
BRANCH=None
BUG=b:123434029
TEST=make buildall;
TEST=make BOARD=ampton, re-flash the DUT, see if the body detection
works
Signed-off-by: Ching-Kang Yen <chingkang@chromium.org>
Change-Id: Ib444abb6bdfbc637539103d563b515817865acc9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2452133
Reviewed-by: Heng-ruey Hsu <henryhsu@chromium.org>
Diffstat (limited to 'common/body_detection.c')
| -rw-r--r-- | common/body_detection.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/common/body_detection.c b/common/body_detection.c index 334009e320..375b4456d0 100644 --- a/common/body_detection.c +++ b/common/body_detection.c @@ -48,18 +48,18 @@ static struct body_detect_motion_data * x_0: oldest value in the window, will be replaced by x_n * x_n: new coming value * - * n^2 * var(x') = n^2 * var(x) + (sum(x') - sum(x))^2 + - * (n * x_n - sum(x'))^2 / n - (n * x_0 - sum(x'))^2 / n + * n^2 * var(x') = n^2 * var(x) + (x_n - x_0) * + * (n * (x_n + x_0) - sum(x') - sum(x)) */ static void update_motion_data(struct body_detect_motion_data *x, int x_n) { const int n = window_size; const int x_0 = x->history[history_idx]; - const int new_sum = x->sum + (x_n - x->history[history_idx]); + const int sum_diff = x_n - x_0; + const int new_sum = x->sum + sum_diff; - x->n2_variance = x->n2_variance + POW2((int64_t)new_sum - x->sum) + - (POW2((int64_t)x_n * n - new_sum) - - POW2((int64_t)x_0 * n - new_sum)) / n; + x->n2_variance += sum_diff * + ((int64_t)n * (x_n + x_0) - new_sum - x->sum); x->sum = new_sum; x->history[history_idx] = x_n; } |