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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
commit | 6bf0a5cb5034a7e684dcc3500e841785237ce2dd (patch) | |
tree | a68f146d7fa01f0134297619fbe7e33db084e0aa /third_party/libwebrtc/common_audio/vad/vad_gmm.c | |
parent | Initial commit. (diff) | |
download | thunderbird-upstream.tar.xz thunderbird-upstream.zip |
Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/libwebrtc/common_audio/vad/vad_gmm.c')
-rw-r--r-- | third_party/libwebrtc/common_audio/vad/vad_gmm.c | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/third_party/libwebrtc/common_audio/vad/vad_gmm.c b/third_party/libwebrtc/common_audio/vad/vad_gmm.c new file mode 100644 index 0000000000..4a7fe67d09 --- /dev/null +++ b/third_party/libwebrtc/common_audio/vad/vad_gmm.c @@ -0,0 +1,82 @@ +/* + * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved. + * + * Use of this source code is governed by a BSD-style license + * that can be found in the LICENSE file in the root of the source + * tree. An additional intellectual property rights grant can be found + * in the file PATENTS. All contributing project authors may + * be found in the AUTHORS file in the root of the source tree. + */ + +#include "common_audio/vad/vad_gmm.h" + +#include "common_audio/signal_processing/include/signal_processing_library.h" + +static const int32_t kCompVar = 22005; +static const int16_t kLog2Exp = 5909; // log2(exp(1)) in Q12. + +// For a normal distribution, the probability of `input` is calculated and +// returned (in Q20). The formula for normal distributed probability is +// +// 1 / s * exp(-(x - m)^2 / (2 * s^2)) +// +// where the parameters are given in the following Q domains: +// m = `mean` (Q7) +// s = `std` (Q7) +// x = `input` (Q4) +// in addition to the probability we output `delta` (in Q11) used when updating +// the noise/speech model. +int32_t WebRtcVad_GaussianProbability(int16_t input, + int16_t mean, + int16_t std, + int16_t* delta) { + int16_t tmp16, inv_std, inv_std2, exp_value = 0; + int32_t tmp32; + + // Calculate `inv_std` = 1 / s, in Q10. + // 131072 = 1 in Q17, and (`std` >> 1) is for rounding instead of truncation. + // Q-domain: Q17 / Q7 = Q10. + tmp32 = (int32_t) 131072 + (int32_t) (std >> 1); + inv_std = (int16_t) WebRtcSpl_DivW32W16(tmp32, std); + + // Calculate `inv_std2` = 1 / s^2, in Q14. + tmp16 = (inv_std >> 2); // Q10 -> Q8. + // Q-domain: (Q8 * Q8) >> 2 = Q14. + inv_std2 = (int16_t)((tmp16 * tmp16) >> 2); + // TODO(bjornv): Investigate if changing to + // inv_std2 = (int16_t)((inv_std * inv_std) >> 6); + // gives better accuracy. + + tmp16 = (input << 3); // Q4 -> Q7 + tmp16 = tmp16 - mean; // Q7 - Q7 = Q7 + + // To be used later, when updating noise/speech model. + // `delta` = (x - m) / s^2, in Q11. + // Q-domain: (Q14 * Q7) >> 10 = Q11. + *delta = (int16_t)((inv_std2 * tmp16) >> 10); + + // Calculate the exponent `tmp32` = (x - m)^2 / (2 * s^2), in Q10. Replacing + // division by two with one shift. + // Q-domain: (Q11 * Q7) >> 8 = Q10. + tmp32 = (*delta * tmp16) >> 9; + + // If the exponent is small enough to give a non-zero probability we calculate + // `exp_value` ~= exp(-(x - m)^2 / (2 * s^2)) + // ~= exp2(-log2(exp(1)) * `tmp32`). + if (tmp32 < kCompVar) { + // Calculate `tmp16` = log2(exp(1)) * `tmp32`, in Q10. + // Q-domain: (Q12 * Q10) >> 12 = Q10. + tmp16 = (int16_t)((kLog2Exp * tmp32) >> 12); + tmp16 = -tmp16; + exp_value = (0x0400 | (tmp16 & 0x03FF)); + tmp16 ^= 0xFFFF; + tmp16 >>= 10; + tmp16 += 1; + // Get `exp_value` = exp(-`tmp32`) in Q10. + exp_value >>= tmp16; + } + + // Calculate and return (1 / s) * exp(-(x - m)^2 / (2 * s^2)), in Q20. + // Q-domain: Q10 * Q10 = Q20. + return inv_std * exp_value; +} |