Add inverted lags index to simplify the loop in
`FindBestPitchPeriod48kHz()`. Instead of looping over 294 items,
only loop over the relevant ones (up to 10) by keeping track of
the relevant indexes.
The benchmark has shown a slight improvement (about +6x).
Benchmarked as follows:
```
out/release/modules_unittests \
--gtest_filter=*RnnVadTest.DISABLED_RnnVadPerformance* \
--gtest_also_run_disabled_tests --logs
```
Results:
| baseline | this CL
------+----------------------+------------------------
run 1 | 22.8319 +/- 1.46554 | 22.1951 +/- 0.747611
| 389.367x | 400.539x
------+----------------------+------------------------
run 2 | 22.4286 +/- 0.726449 | 22.2718 +/- 0.963738
| 396.369x | 399.16x
------+----------------------+------------------------
run 2 | 22.5688 +/- 0.831341 | 22.4166 +/- 0.953362
| 393.906x | 396.581x
This CL also moved `PitchPseudoInterpolationInvLagAutoCorr()`
into `FindBestPitchPeriod48kHz()`.
Bug: webrtc:10480
Change-Id: Id4e6d755045c3198a80fa94a0a7463577d909b7e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/191764
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32590}
05f5d636e5