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Diffstat (limited to 'chromium/third_party/webrtc/modules/audio_coding/neteq/dtmf_tone_generator.cc')
| -rw-r--r-- | chromium/third_party/webrtc/modules/audio_coding/neteq/dtmf_tone_generator.cc | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/chromium/third_party/webrtc/modules/audio_coding/neteq/dtmf_tone_generator.cc b/chromium/third_party/webrtc/modules/audio_coding/neteq/dtmf_tone_generator.cc new file mode 100644 index 00000000000..34c615d70f6 --- /dev/null +++ b/chromium/third_party/webrtc/modules/audio_coding/neteq/dtmf_tone_generator.cc @@ -0,0 +1,192 @@ +/* + * 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(int num_samples, + AudioMultiVector* output) { + if (!initialized_) { + return kNotInitialized; + } + + if (num_samples < 0 || !output) { + return kParameterError; + } + assert(output->Channels() == 1); // Not adapted for multi-channel yet. + if (output->Channels() != 1) { + return kStereoNotSupported; + } + + output->AssertSize(num_samples); + for (int 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); + } + + return num_samples; +} + +} // namespace webrtc |