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opus_pvq: improve PVQ search for low Ks 

Since the probelm mentioned only happened when the phase was negative
(e.g. the sum had to be decreased), only discarding dimensions with a
zero pulse in that case restored the search's previously low distortion
at low Ks when the phase is never negative.

Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
This commit is contained in:
Rostislav Pehlivanov 2017-02-24 07:03:12 +00:00
parent 0d85c7bb5a
commit 22b8ada7b5
1 changed files with 5 additions and 2 deletions
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7
libavcodec/opus_pvq.c
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@ -413,11 +413,14 @@ static void celt_pvq_search(float *X, int *y, int K, int N)
y_norm += 1.0f;
for (i = 0; i < N; i++) {
/* If the sum has been overshot and the best place has 0 pulses allocated
* to it, attempting to decrease it further will actually increase the
* sum. Prevent this by disregarding any 0 positions when decrementing. */
const int ca = 1 ^ ((y[i] == 0) & (phase < 0));
float xy_new = xy_norm + 1*phase*FFABS(X[i]);
float y_new = y_norm + 2*phase*FFABS(y[i]);
xy_new = xy_new * xy_new;
/* FIXME: the y[i] check makes the search slightly worse at Ks below 5 */
if (y[i] && (max_den*xy_new) > (y_new*max_num)) {
if (ca && (max_den*xy_new) > (y_new*max_num)) {
max_den = y_new;
max_num = xy_new;
max_idx = i;