| /* |
| * Copyright (c) 2012 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. |
| */ |
| |
| // This class provides a generator for DTMF tones. The tone generation is based |
| // on a sinusoid recursion. Each sinusoid is generated using a recursion |
| // formula; x[n] = a * x[n-1] - x[n-2], where the coefficient |
| // a = 2*cos(2*pi*f/fs). The recursion is started with x[-1] = 0 and |
| // x[-2] = sin(2*pi*f/fs). (Note that with this initialization, the resulting |
| // sinusoid gets a "negative" rotation; x[n] = sin(-2*pi*f/fs * n + phi), but |
| // kept this way due to historical reasons.) |
| // TODO(hlundin): Change to positive rotation? |
| // |
| // Each key on the telephone keypad corresponds to an "event", 0-15. Each event |
| // is mapped to a tone pair, with a low and a high frequency. There are four |
| // low and four high frequencies, each corresponding to a row and column, |
| // respectively, on the keypad as illustrated below. |
| // |
| // 1209 Hz 1336 Hz 1477 Hz 1633 Hz |
| // 697 Hz 1 2 3 12 |
| // 770 Hz 4 5 6 13 |
| // 852 Hz 7 8 9 14 |
| // 941 Hz 10 0 11 15 |
| |
| #include "webrtc/modules/audio_coding/neteq/dtmf_tone_generator.h" |
| |
| #include <assert.h> |
| |
| namespace webrtc { |
| |
| // The filter coefficient a = 2*cos(2*pi*f/fs) for the low frequency tone, for |
| // sample rates fs = {8000, 16000, 32000, 48000} Hz, and events 0 through 15. |
| // Values are in Q14. |
| const int DtmfToneGenerator::kCoeff1[4][16] = { |
| { 24219, 27980, 27980, 27980, 26956, 26956, 26956, 25701, 25701, 25701, |
| 24219, 24219, 27980, 26956, 25701, 24219 }, |
| { 30556, 31548, 31548, 31548, 31281, 31281, 31281, 30951, 30951, 30951, |
| 30556, 30556, 31548, 31281, 30951, 30556 }, |
| { 32210, 32462, 32462, 32462, 32394, 32394, 32394, 32311, 32311, 32311, |
| 32210, 32210, 32462, 32394, 32311, 32210 }, |
| { 32520, 32632, 32632, 32632, 32602, 32602, 32602, 32564, 32564, 32564, |
| 32520, 32520, 32632, 32602, 32564, 32520 } }; |
| |
| // The filter coefficient a = 2*cos(2*pi*f/fs) for the high frequency tone, for |
| // sample rates fs = {8000, 16000, 32000, 48000} Hz, and events 0 through 15. |
| // Values are in Q14. |
| const int DtmfToneGenerator::kCoeff2[4][16] = { |
| { 16325, 19073, 16325, 13085, 19073, 16325, 13085, 19073, 16325, 13085, |
| 19073, 13085, 9315, 9315, 9315, 9315}, |
| { 28361, 29144, 28361, 27409, 29144, 28361, 27409, 29144, 28361, 27409, |
| 29144, 27409, 26258, 26258, 26258, 26258}, |
| { 31647, 31849, 31647, 31400, 31849, 31647, 31400, 31849, 31647, 31400, |
| 31849, 31400, 31098, 31098, 31098, 31098}, |
| { 32268, 32359, 32268, 32157, 32359, 32268, 32157, 32359, 32268, 32157, |
| 32359, 32157, 32022, 32022, 32022, 32022} }; |
| |
| // The initialization value x[-2] = sin(2*pi*f/fs) for the low frequency tone, |
| // for sample rates fs = {8000, 16000, 32000, 48000} Hz, and events 0-15. |
| // Values are in Q14. |
| const int DtmfToneGenerator::kInitValue1[4][16] = { |
| { 11036, 8528, 8528, 8528, 9315, 9315, 9315, 10163, 10163, 10163, 11036, |
| 11036, 8528, 9315, 10163, 11036}, |
| { 5918, 4429, 4429, 4429, 4879, 4879, 4879, 5380, 5380, 5380, 5918, 5918, |
| 4429, 4879, 5380, 5918}, |
| { 3010, 2235, 2235, 2235, 2468, 2468, 2468, 2728, 2728, 2728, 3010, 3010, |
| 2235, 2468, 2728, 3010}, |
| { 2013, 1493, 1493, 1493, 1649, 1649, 1649, 1823, 1823, 1823, 2013, 2013, |
| 1493, 1649, 1823, 2013 } }; |
| |
| // The initialization value x[-2] = sin(2*pi*f/fs) for the high frequency tone, |
| // for sample rates fs = {8000, 16000, 32000, 48000} Hz, and events 0-15. |
| // Values are in Q14. |
| const int DtmfToneGenerator::kInitValue2[4][16] = { |
| { 14206, 13323, 14206, 15021, 13323, 14206, 15021, 13323, 14206, 15021, |
| 13323, 15021, 15708, 15708, 15708, 15708}, |
| { 8207, 7490, 8207, 8979, 7490, 8207, 8979, 7490, 8207, 8979, 7490, 8979, |
| 9801, 9801, 9801, 9801}, |
| { 4249, 3853, 4249, 4685, 3853, 4249, 4685, 3853, 4249, 4685, 3853, 4685, |
| 5164, 5164, 5164, 5164}, |
| { 2851, 2582, 2851, 3148, 2582, 2851, 3148, 2582, 2851, 3148, 2582, 3148, |
| 3476, 3476, 3476, 3476} }; |
| |
| // Amplitude multipliers for volume values 0 through 36, corresponding to |
| // 0 dBm0 through -36 dBm0. Values are in Q14. |
| const int DtmfToneGenerator::kAmplitude[37] = { |
| 16141, 14386, 12821, 11427, 10184, 9077, 8090, 7210, 6426, 5727, 5104, 4549, |
| 4054, 3614, 3221, 2870, 2558, 2280, 2032, 1811, 1614, 1439, 1282, 1143, |
| 1018, 908, 809, 721, 643, 573, 510, 455, 405, 361, 322, 287, 256 }; |
| |
| // Constructor. |
| DtmfToneGenerator::DtmfToneGenerator() |
| : initialized_(false), |
| coeff1_(0), |
| coeff2_(0), |
| amplitude_(0) { |
| } |
| |
| // Initialize the DTMF generator with sample rate fs Hz (8000, 16000, 32000, |
| // 48000), event (0-15) and attenuation (0-36 dB). |
| // Returns 0 on success, otherwise an error code. |
| int DtmfToneGenerator::Init(int fs, int event, int attenuation) { |
| initialized_ = false; |
| int fs_index; |
| if (fs == 8000) { |
| fs_index = 0; |
| } else if (fs == 16000) { |
| fs_index = 1; |
| } else if (fs == 32000) { |
| fs_index = 2; |
| } else if (fs == 48000) { |
| fs_index = 3; |
| } else { |
| assert(false); |
| fs_index = 1; // Default to 8000 Hz. |
| } |
| |
| if (event < 0 || event > 15) { |
| return kParameterError; // Invalid event number. |
| } |
| |
| if (attenuation < 0 || attenuation > 36) { |
| return kParameterError; // Invalid attenuation. |
| } |
| |
| // Look up oscillator coefficient for low and high frequencies. |
| coeff1_ = kCoeff1[fs_index][event]; |
| coeff2_ = kCoeff2[fs_index][event]; |
| // Look up amplitude multiplier. |
| amplitude_ = kAmplitude[attenuation]; |
| // Initialize sample history. |
| sample_history1_[0] = kInitValue1[fs_index][event]; |
| sample_history1_[1] = 0; |
| sample_history2_[0] = kInitValue2[fs_index][event]; |
| sample_history2_[1] = 0; |
| |
| initialized_ = true; |
| return 0; |
| } |
| |
| // Reset tone generator to uninitialized state. |
| void DtmfToneGenerator::Reset() { |
| initialized_ = false; |
| } |
| |
| // Generate num_samples of DTMF signal and write to |output|. |
| int DtmfToneGenerator::Generate(size_t num_samples, |
| AudioMultiVector* output) { |
| if (!initialized_) { |
| return kNotInitialized; |
| } |
| |
| if (!output) { |
| return kParameterError; |
| } |
| |
| output->AssertSize(num_samples); |
| for (size_t i = 0; i < num_samples; ++i) { |
| // Use recursion formula y[n] = a * y[n - 1] - y[n - 2]. |
| int16_t temp_val_low = ((coeff1_ * sample_history1_[1] + 8192) >> 14) |
| - sample_history1_[0]; |
| int16_t temp_val_high = ((coeff2_ * sample_history2_[1] + 8192) >> 14) |
| - sample_history2_[0]; |
| |
| // Update recursion memory. |
| sample_history1_[0] = sample_history1_[1]; |
| sample_history1_[1] = temp_val_low; |
| sample_history2_[0] = sample_history2_[1]; |
| sample_history2_[1] = temp_val_high; |
| |
| // Attenuate the low frequency tone 3 dB. |
| int32_t temp_val = kAmpMultiplier * temp_val_low + (temp_val_high << 15); |
| // Normalize the signal to Q14 with proper rounding. |
| temp_val = (temp_val + 16384) >> 15; |
| // Scale the signal to correct volume. |
| (*output)[0][i] = |
| static_cast<int16_t>((temp_val * amplitude_ + 8192) >> 14); |
| } |
| // Copy first channel to all other channels. |
| for (size_t channel = 1; channel < output->Channels(); ++channel) { |
| output->CopyChannel(0, channel); |
| } |
| |
| return static_cast<int>(num_samples); |
| } |
| |
| bool DtmfToneGenerator::initialized() const { |
| return initialized_; |
| } |
| |
| } // namespace webrtc |