whisper.cpp/examples/common.cpp

#include "common.h"

// third-party utilities
// use your favorite implementations
#define DR_WAV_IMPLEMENTATION
#include "dr_wav.h"

#include <cmath>
#include <regex>

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

std::string trim(const std::string & s) {
    std::regex e("^\\s+|\\s+$");
    return std::regex_replace(s, e, "");
}

std::string replace(const std::string & s, const std::string & from, const std::string & to) {
    std::string result = s;
    size_t pos = 0;
    while ((pos = result.find(from, pos)) != std::string::npos) {
        result.replace(pos, from.length(), to);
        pos += to.length();
    }
    return result;
}

bool read_wav(const std::string & fname, std::vector<float>& pcmf32, std::vector<std::vector<float>>& pcmf32s, bool stereo) {
    drwav wav;
    std::vector<uint8_t> wav_data; // used for pipe input from stdin

    if (fname == "-") {
        {
            uint8_t buf[1024];
            while (true)
            {
                const size_t n = fread(buf, 1, sizeof(buf), stdin);
                if (n == 0) {
                    break;
                }
                wav_data.insert(wav_data.end(), buf, buf + n);
            }
        }

        if (drwav_init_memory(&wav, wav_data.data(), wav_data.size(), nullptr) == false) {
            fprintf(stderr, "error: failed to open WAV file from stdin\n");
            return false;
        }

        fprintf(stderr, "%s: read %zu bytes from stdin\n", __func__, wav_data.size());
    }
    else if (drwav_init_file(&wav, fname.c_str(), nullptr) == false) {
        fprintf(stderr, "error: failed to open '%s' as WAV file\n", fname.c_str());
        return false;
    }

    if (wav.channels != 1 && wav.channels != 2) {
        fprintf(stderr, "%s: WAV file '%s' must be mono or stereo\n", __func__, fname.c_str());
        return false;
    }

    if (stereo && wav.channels != 2) {
        fprintf(stderr, "%s: WAV file '%s' must be stereo for diarization\n", __func__, fname.c_str());
        return false;
    }

    if (wav.sampleRate != COMMON_SAMPLE_RATE) {
        fprintf(stderr, "%s: WAV file '%s' must be %i kHz\n", __func__, fname.c_str(), COMMON_SAMPLE_RATE/1000);
        return false;
    }

    if (wav.bitsPerSample != 16) {
        fprintf(stderr, "%s: WAV file '%s' must be 16-bit\n", __func__, fname.c_str());
        return false;
    }

    const uint64_t n = wav_data.empty() ? wav.totalPCMFrameCount : wav_data.size()/(wav.channels*wav.bitsPerSample/8);

    std::vector<int16_t> pcm16;
    pcm16.resize(n*wav.channels);
    drwav_read_pcm_frames_s16(&wav, n, pcm16.data());
    drwav_uninit(&wav);

    // convert to mono, float
    pcmf32.resize(n);
    if (wav.channels == 1) {
        for (uint64_t i = 0; i < n; i++) {
            pcmf32[i] = float(pcm16[i])/32768.0f;
        }
    } else {
        for (uint64_t i = 0; i < n; i++) {
            pcmf32[i] = float(pcm16[2*i] + pcm16[2*i + 1])/65536.0f;
        }
    }

    if (stereo) {
        // convert to stereo, float
        pcmf32s.resize(2);

        pcmf32s[0].resize(n);
        pcmf32s[1].resize(n);
        for (uint64_t i = 0; i < n; i++) {
            pcmf32s[0][i] = float(pcm16[2*i])/32768.0f;
            pcmf32s[1][i] = float(pcm16[2*i + 1])/32768.0f;
        }
    }

    return true;
}

void high_pass_filter(std::vector<float> & data, float cutoff, float sample_rate) {
    const float rc = 1.0f / (2.0f * M_PI * cutoff);
    const float dt = 1.0f / sample_rate;
    const float alpha = dt / (rc + dt);

    float y = data[0];

    for (size_t i = 1; i < data.size(); i++) {
        y = alpha * (y + data[i] - data[i - 1]);
        data[i] = y;
    }
}

bool vad_simple(std::vector<float> & pcmf32, int sample_rate, int last_ms, float vad_thold, float freq_thold, bool verbose) {
    const int n_samples      = pcmf32.size();
    const int n_samples_last = (sample_rate * last_ms) / 1000;

    if (n_samples_last >= n_samples) {
        // not enough samples - assume no speech
        return false;
    }

    if (freq_thold > 0.0f) {
        high_pass_filter(pcmf32, freq_thold, sample_rate);
    }

    float energy_all  = 0.0f;
    float energy_last = 0.0f;

    for (int i = 0; i < n_samples; i++) {
        energy_all += fabsf(pcmf32[i]);

        if (i >= n_samples - n_samples_last) {
            energy_last += fabsf(pcmf32[i]);
        }
    }

    energy_all  /= n_samples;
    energy_last /= n_samples_last;

    if (verbose) {
        fprintf(stderr, "%s: energy_all: %f, energy_last: %f, vad_thold: %f, freq_thold: %f\n", __func__, energy_all, energy_last, vad_thold, freq_thold);
    }

    if (energy_last > vad_thold*energy_all) {
        return false;
    }

    return true;
}