whisper.cpp/examples/server/server.cpp

#include "common.h"

#include "whisper.h"
#include "httplib.h"
#include "json.hpp"

#include <cmath>
#include <fstream>
#include <cstdio>
#include <string>
#include <thread>
#include <vector>
#include <cstring>

#if defined(_MSC_VER)
#pragma warning(disable: 4244 4267) // possible loss of data
#endif

using namespace httplib;
using json = nlohmann::json;

namespace {

// Terminal color map. 10 colors grouped in ranges [0.0, 0.1, ..., 0.9]
// Lowest is red, middle is yellow, highest is green.
const std::vector<std::string> k_colors = {
    "\033[38;5;196m", "\033[38;5;202m", "\033[38;5;208m", "\033[38;5;214m", "\033[38;5;220m",
    "\033[38;5;226m", "\033[38;5;190m", "\033[38;5;154m", "\033[38;5;118m", "\033[38;5;82m",
};

// output formats
const std::string json_format   = "json";
const std::string text_format   = "text";
const std::string srt_format    = "srt";
const std::string vjson_format  = "verbose_json";
const std::string vtt_format    = "vtt";

struct server_params
{
    std::string hostname = "127.0.0.1";
    std::string public_path = "examples/server/public";

    int32_t port          = 8080;
    int32_t read_timeout  = 600;
    int32_t write_timeout = 600;
};

struct whisper_params {
    int32_t n_threads    = std::min(4, (int32_t) std::thread::hardware_concurrency());
    int32_t n_processors =  1;
    int32_t offset_t_ms  =  0;
    int32_t offset_n     =  0;
    int32_t duration_ms  =  0;
    int32_t progress_step =  5;
    int32_t max_context  = -1;
    int32_t max_len      =  0;
    int32_t best_of      =  2;
    int32_t beam_size    = -1;

    float word_thold    =  0.01f;
    float entropy_thold =  2.40f;
    float logprob_thold = -1.00f;
    float userdef_temp  =  0.20f;

    bool speed_up        = false;
    bool debug_mode      = false;
    bool translate       = false;
    bool detect_language = false;
    bool diarize         = false;
    bool tinydiarize     = false;
    bool split_on_word   = false;
    bool no_fallback     = false;
    bool print_special   = false;
    bool print_colors    = false;
    bool print_realtime  = false;
    bool print_progress  = false;
    bool no_timestamps   = false;
    bool use_gpu         = true;

    std::string language        = "en";
    std::string prompt          = "";
    std::string font_path       = "/System/Library/Fonts/Supplemental/Courier New Bold.ttf";
    std::string model           = "models/ggml-base.en.bin";

    std::string response_format     = json_format;

    // [TDRZ] speaker turn string
    std::string tdrz_speaker_turn = " [SPEAKER_TURN]"; // TODO: set from command line

    std::string openvino_encode_device = "CPU";
};

//  500 -> 00:05.000
// 6000 -> 01:00.000
std::string to_timestamp(int64_t t, bool comma = false) {
    int64_t msec = t * 10;
    int64_t hr = msec / (1000 * 60 * 60);
    msec = msec - hr * (1000 * 60 * 60);
    int64_t min = msec / (1000 * 60);
    msec = msec - min * (1000 * 60);
    int64_t sec = msec / 1000;
    msec = msec - sec * 1000;

    char buf[32];
    snprintf(buf, sizeof(buf), "%02d:%02d:%02d%s%03d", (int) hr, (int) min, (int) sec, comma ? "," : ".", (int) msec);

    return std::string(buf);
}

int timestamp_to_sample(int64_t t, int n_samples) {
    return std::max(0, std::min((int) n_samples - 1, (int) ((t*WHISPER_SAMPLE_RATE)/100)));
}

bool is_file_exist(const char *fileName)
{
    std::ifstream infile(fileName);
    return infile.good();
}

void whisper_print_usage(int /*argc*/, char ** argv, const whisper_params & params,
                         const server_params& sparams) {
    fprintf(stderr, "\n");
    fprintf(stderr, "usage: %s [options] \n", argv[0]);
    fprintf(stderr, "\n");
    fprintf(stderr, "options:\n");
    fprintf(stderr, "  -h,        --help              [default] show this help message and exit\n");
    fprintf(stderr, "  -t N,      --threads N         [%-7d] number of threads to use during computation\n",    params.n_threads);
    fprintf(stderr, "  -p N,      --processors N      [%-7d] number of processors to use during computation\n", params.n_processors);
    fprintf(stderr, "  -ot N,     --offset-t N        [%-7d] time offset in milliseconds\n",                    params.offset_t_ms);
    fprintf(stderr, "  -on N,     --offset-n N        [%-7d] segment index offset\n",                           params.offset_n);
    fprintf(stderr, "  -d  N,     --duration N        [%-7d] duration of audio to process in milliseconds\n",   params.duration_ms);
    fprintf(stderr, "  -mc N,     --max-context N     [%-7d] maximum number of text context tokens to store\n", params.max_context);
    fprintf(stderr, "  -ml N,     --max-len N         [%-7d] maximum segment length in characters\n",           params.max_len);
    fprintf(stderr, "  -sow,      --split-on-word     [%-7s] split on word rather than on token\n",             params.split_on_word ? "true" : "false");
    fprintf(stderr, "  -bo N,     --best-of N         [%-7d] number of best candidates to keep\n",              params.best_of);
    fprintf(stderr, "  -bs N,     --beam-size N       [%-7d] beam size for beam search\n",                      params.beam_size);
    fprintf(stderr, "  -wt N,     --word-thold N      [%-7.2f] word timestamp probability threshold\n",         params.word_thold);
    fprintf(stderr, "  -et N,     --entropy-thold N   [%-7.2f] entropy threshold for decoder fail\n",           params.entropy_thold);
    fprintf(stderr, "  -lpt N,    --logprob-thold N   [%-7.2f] log probability threshold for decoder fail\n",   params.logprob_thold);
    // fprintf(stderr, "  -su,       --speed-up          [%-7s] speed up audio by x2 (reduced accuracy)\n",        params.speed_up ? "true" : "false");
    fprintf(stderr, "  -debug,    --debug-mode        [%-7s] enable debug mode (eg. dump log_mel)\n",           params.debug_mode ? "true" : "false");
    fprintf(stderr, "  -tr,       --translate         [%-7s] translate from source language to english\n",      params.translate ? "true" : "false");
    fprintf(stderr, "  -di,       --diarize           [%-7s] stereo audio diarization\n",                       params.diarize ? "true" : "false");
    fprintf(stderr, "  -tdrz,     --tinydiarize       [%-7s] enable tinydiarize (requires a tdrz model)\n",     params.tinydiarize ? "true" : "false");
    fprintf(stderr, "  -nf,       --no-fallback       [%-7s] do not use temperature fallback while decoding\n", params.no_fallback ? "true" : "false");
    fprintf(stderr, "  -ps,       --print-special     [%-7s] print special tokens\n",                           params.print_special ? "true" : "false");
    fprintf(stderr, "  -pc,       --print-colors      [%-7s] print colors\n",                                   params.print_colors ? "true" : "false");
    fprintf(stderr, "  -pr,       --print-realtime    [%-7s] print output in realtime\n",                       params.print_realtime ? "true" : "false");
    fprintf(stderr, "  -pp,       --print-progress    [%-7s] print progress\n",                                 params.print_progress ? "true" : "false");
    fprintf(stderr, "  -nt,       --no-timestamps     [%-7s] do not print timestamps\n",                        params.no_timestamps ? "true" : "false");
    fprintf(stderr, "  -l LANG,   --language LANG     [%-7s] spoken language ('auto' for auto-detect)\n",       params.language.c_str());
    fprintf(stderr, "  -dl,       --detect-language   [%-7s] exit after automatically detecting language\n",    params.detect_language ? "true" : "false");
    fprintf(stderr, "             --prompt PROMPT     [%-7s] initial prompt\n",                                 params.prompt.c_str());
    fprintf(stderr, "  -m FNAME,  --model FNAME       [%-7s] model path\n",                                     params.model.c_str());
    fprintf(stderr, "  -oved D,   --ov-e-device DNAME [%-7s] the OpenVINO device used for encode inference\n",  params.openvino_encode_device.c_str());
    // server params
    fprintf(stderr, "  --host HOST,                   [%-7s] Hostname/ip-adress for the server\n", sparams.hostname.c_str());
    fprintf(stderr, "  --port PORT,                   [%-7d] Port number for the server\n", sparams.port);
    fprintf(stderr, "  --public PATH,                 [%-7s] Path to the public folder\n", sparams.public_path.c_str());
    fprintf(stderr, "\n");
}

bool whisper_params_parse(int argc, char ** argv, whisper_params & params, server_params & sparams) {
    for (int i = 1; i < argc; i++) {
        std::string arg = argv[i];

        if (arg == "-h" || arg == "--help") {
            whisper_print_usage(argc, argv, params, sparams);
            exit(0);
        }
        else if (arg == "-t"    || arg == "--threads")         { params.n_threads       = std::stoi(argv[++i]); }
        else if (arg == "-p"    || arg == "--processors")      { params.n_processors    = std::stoi(argv[++i]); }
        else if (arg == "-ot"   || arg == "--offset-t")        { params.offset_t_ms     = std::stoi(argv[++i]); }
        else if (arg == "-on"   || arg == "--offset-n")        { params.offset_n        = std::stoi(argv[++i]); }
        else if (arg == "-d"    || arg == "--duration")        { params.duration_ms     = std::stoi(argv[++i]); }
        else if (arg == "-mc"   || arg == "--max-context")     { params.max_context     = std::stoi(argv[++i]); }
        else if (arg == "-ml"   || arg == "--max-len")         { params.max_len         = std::stoi(argv[++i]); }
        else if (arg == "-bo"   || arg == "--best-of")         { params.best_of         = std::stoi(argv[++i]); }
        else if (arg == "-bs"   || arg == "--beam-size")       { params.beam_size       = std::stoi(argv[++i]); }
        else if (arg == "-wt"   || arg == "--word-thold")      { params.word_thold      = std::stof(argv[++i]); }
        else if (arg == "-et"   || arg == "--entropy-thold")   { params.entropy_thold   = std::stof(argv[++i]); }
        else if (arg == "-lpt"  || arg == "--logprob-thold")   { params.logprob_thold   = std::stof(argv[++i]); }
        // else if (arg == "-su"   || arg == "--speed-up")        { params.speed_up        = true; }
        else if (arg == "-debug"|| arg == "--debug-mode")      { params.debug_mode      = true; }
        else if (arg == "-tr"   || arg == "--translate")       { params.translate       = true; }
        else if (arg == "-di"   || arg == "--diarize")         { params.diarize         = true; }
        else if (arg == "-tdrz" || arg == "--tinydiarize")     { params.tinydiarize     = true; }
        else if (arg == "-sow"  || arg == "--split-on-word")   { params.split_on_word   = true; }
        else if (arg == "-nf"   || arg == "--no-fallback")     { params.no_fallback     = true; }
        else if (arg == "-fp"   || arg == "--font-path")       { params.font_path       = argv[++i]; }
        else if (arg == "-ps"   || arg == "--print-special")   { params.print_special   = true; }
        else if (arg == "-pc"   || arg == "--print-colors")    { params.print_colors    = true; }
        else if (arg == "-pr"   || arg == "--print-realtime")  { params.print_realtime  = true; }
        else if (arg == "-pp"   || arg == "--print-progress")  { params.print_progress  = true; }
        else if (arg == "-nt"   || arg == "--no-timestamps")   { params.no_timestamps   = true; }
        else if (arg == "-l"    || arg == "--language")        { params.language        = argv[++i]; }
        else if (arg == "-dl"   || arg == "--detect-language") { params.detect_language = true; }
        else if (                  arg == "--prompt")          { params.prompt          = argv[++i]; }
        else if (arg == "-m"    || arg == "--model")           { params.model           = argv[++i]; }
        else if (arg == "-oved" || arg == "--ov-e-device")     { params.openvino_encode_device = argv[++i]; }
        else if (arg == "-ng"   || arg == "--no-gpu")          { params.use_gpu         = false; }
        // server params
        else if (                  arg == "--port")            { sparams.port        = std::stoi(argv[++i]); }
        else if (                  arg == "--host")            { sparams.hostname    = argv[++i]; }
        else if (                  arg == "--public")          { sparams.public_path = argv[++i]; }
        else {
            fprintf(stderr, "error: unknown argument: %s\n", arg.c_str());
            whisper_print_usage(argc, argv, params, sparams);
            exit(0);
        }
    }

    return true;
}

struct whisper_print_user_data {
    const whisper_params * params;

    const std::vector<std::vector<float>> * pcmf32s;
    int progress_prev;
};

std::string estimate_diarization_speaker(std::vector<std::vector<float>> pcmf32s, int64_t t0, int64_t t1, bool id_only = false) {
    std::string speaker = "";
    const int64_t n_samples = pcmf32s[0].size();

    const int64_t is0 = timestamp_to_sample(t0, n_samples);
    const int64_t is1 = timestamp_to_sample(t1, n_samples);

    double energy0 = 0.0f;
    double energy1 = 0.0f;

    for (int64_t j = is0; j < is1; j++) {
        energy0 += fabs(pcmf32s[0][j]);
        energy1 += fabs(pcmf32s[1][j]);
    }

    if (energy0 > 1.1*energy1) {
        speaker = "0";
    } else if (energy1 > 1.1*energy0) {
        speaker = "1";
    } else {
        speaker = "?";
    }

    //printf("is0 = %lld, is1 = %lld, energy0 = %f, energy1 = %f, speaker = %s\n", is0, is1, energy0, energy1, speaker.c_str());

    if (!id_only) {
        speaker.insert(0, "(speaker ");
        speaker.append(")");
    }

    return speaker;
}

void whisper_print_progress_callback(struct whisper_context * /*ctx*/, struct whisper_state * /*state*/, int progress, void * user_data) {
    int progress_step = ((whisper_print_user_data *) user_data)->params->progress_step;
    int * progress_prev  = &(((whisper_print_user_data *) user_data)->progress_prev);
    if (progress >= *progress_prev + progress_step) {
        *progress_prev += progress_step;
        fprintf(stderr, "%s: progress = %3d%%\n", __func__, progress);
    }
}

void whisper_print_segment_callback(struct whisper_context * ctx, struct whisper_state * /*state*/, int n_new, void * user_data) {
    const auto & params  = *((whisper_print_user_data *) user_data)->params;
    const auto & pcmf32s = *((whisper_print_user_data *) user_data)->pcmf32s;

    const int n_segments = whisper_full_n_segments(ctx);

    std::string speaker = "";

    int64_t t0 = 0;
    int64_t t1 = 0;

    // print the last n_new segments
    const int s0 = n_segments - n_new;

    if (s0 == 0) {
        printf("\n");
    }

    for (int i = s0; i < n_segments; i++) {
        if (!params.no_timestamps || params.diarize) {
            t0 = whisper_full_get_segment_t0(ctx, i);
            t1 = whisper_full_get_segment_t1(ctx, i);
        }

        if (!params.no_timestamps) {
            printf("[%s --> %s]  ", to_timestamp(t0).c_str(), to_timestamp(t1).c_str());
        }

        if (params.diarize && pcmf32s.size() == 2) {
            speaker = estimate_diarization_speaker(pcmf32s, t0, t1);
        }

        if (params.print_colors) {
            for (int j = 0; j < whisper_full_n_tokens(ctx, i); ++j) {
                if (params.print_special == false) {
                    const whisper_token id = whisper_full_get_token_id(ctx, i, j);
                    if (id >= whisper_token_eot(ctx)) {
                        continue;
                    }
                }

                const char * text = whisper_full_get_token_text(ctx, i, j);
                const float  p    = whisper_full_get_token_p   (ctx, i, j);

                const int col = std::max(0, std::min((int) k_colors.size() - 1, (int) (std::pow(p, 3)*float(k_colors.size()))));

                printf("%s%s%s%s", speaker.c_str(), k_colors[col].c_str(), text, "\033[0m");
            }
        } else {
            const char * text = whisper_full_get_segment_text(ctx, i);

            printf("%s%s", speaker.c_str(), text);
        }

        if (params.tinydiarize) {
            if (whisper_full_get_segment_speaker_turn_next(ctx, i)) {
                printf("%s", params.tdrz_speaker_turn.c_str());
            }
        }

        // with timestamps or speakers: each segment on new line
        if (!params.no_timestamps || params.diarize) {
            printf("\n");
        }
        fflush(stdout);
    }
}

std::string output_str(struct whisper_context * ctx, const whisper_params & params, std::vector<std::vector<float>> pcmf32s) {
    std::stringstream result;
    const int n_segments = whisper_full_n_segments(ctx);
    for (int i = 0; i < n_segments; ++i) {
        const char * text = whisper_full_get_segment_text(ctx, i);
        std::string speaker = "";

        if (params.diarize && pcmf32s.size() == 2)
        {
            const int64_t t0 = whisper_full_get_segment_t0(ctx, i);
            const int64_t t1 = whisper_full_get_segment_t1(ctx, i);
            speaker = estimate_diarization_speaker(pcmf32s, t0, t1);
        }

        result << speaker << text << "\n";
    }
    return result.str();
}

void get_req_parameters(const Request & req, whisper_params & params)
{
    // user model configu.has_fileion
    if (req.has_file("offset-t"))
    {
        params.offset_t_ms = std::stoi(req.get_file_value("offset-t").content);
    }
    if (req.has_file("offset-n"))
    {
        params.offset_n = std::stoi(req.get_file_value("offset-n").content);
    }
    if (req.has_file("duration"))
    {
        params.duration_ms = std::stoi(req.get_file_value("duration").content);
    }
    if (req.has_file("max-context"))
    {
        params.max_context = std::stoi(req.get_file_value("max-context").content);
    }
    if (req.has_file("prompt"))
    {
        params.prompt = req.get_file_value("prompt").content;
    }
    if (req.has_file("response-format"))
    {
        params.response_format = req.get_file_value("response-format").content;
    }
    if (req.has_file("temperature"))
    {
        params.userdef_temp = std::stof(req.get_file_value("temperature").content);
    }
}

}  // namespace

int main(int argc, char ** argv) {
    whisper_params params;
    server_params sparams;

    std::mutex whisper_mutex;

    if (whisper_params_parse(argc, argv, params, sparams) == false) {
        whisper_print_usage(argc, argv, params, sparams);
        return 1;
    }

    if (params.language != "auto" && whisper_lang_id(params.language.c_str()) == -1) {
        fprintf(stderr, "error: unknown language '%s'\n", params.language.c_str());
        whisper_print_usage(argc, argv, params, sparams);
        exit(0);
    }

    if (params.diarize && params.tinydiarize) {
        fprintf(stderr, "error: cannot use both --diarize and --tinydiarize\n");
        whisper_print_usage(argc, argv, params, sparams);
        exit(0);
    }

    // whisper init
    struct whisper_context_params cparams;
    cparams.use_gpu = params.use_gpu;

    struct whisper_context * ctx = whisper_init_from_file_with_params(params.model.c_str(), cparams);

    if (ctx == nullptr) {
        fprintf(stderr, "error: failed to initialize whisper context\n");
        return 3;
    }

    // initialize openvino encoder. this has no effect on whisper.cpp builds that don't have OpenVINO configured
    whisper_ctx_init_openvino_encoder(ctx, nullptr, params.openvino_encode_device.c_str(), nullptr);

    Server svr;

    std::string const default_content = "<html>hello</html>";

    // this is only called if no index.html is found in the public --path
    svr.Get("/", [&default_content](const Request &, Response &res){
        res.set_content(default_content, "text/html");
        return false;
    });

    svr.Post("/inference", [&](const Request &req, Response &res){
        // acquire whisper model mutex lock
        whisper_mutex.lock();

        // first check user requested fields of the request
        if (!req.has_file("file"))
        {
            fprintf(stderr, "error: no 'file' field in the request\n");
            const std::string error_resp = "{\"error\":\"no 'file' field in the request\"}";
            res.set_content(error_resp, "application/json");
            whisper_mutex.unlock();
            return;
        }
        auto audio_file = req.get_file_value("file");

        // check non-required fields
        get_req_parameters(req, params);

        std::string filename{audio_file.filename};
        printf("Received request: %s\n", filename.c_str());

        // audio arrays
        std::vector<float> pcmf32;               // mono-channel F32 PCM
        std::vector<std::vector<float>> pcmf32s; // stereo-channel F32 PCM

        // write to temporary file
        const std::string temp_filename = "whisper_server_temp_file.wav";
        std::ofstream temp_file{temp_filename, std::ios::binary};
        temp_file << audio_file.content;
        temp_file.close();

        // read wav content into pcmf32
        if (!::read_wav(temp_filename, pcmf32, pcmf32s, params.diarize)) {
            fprintf(stderr, "error: failed to read WAV file '%s'\n", temp_filename.c_str());
            const std::string error_resp = "{\"error\":\"failed to read WAV file\"}";
            res.set_content(error_resp, "application/json");
            std::remove(temp_filename.c_str());
            whisper_mutex.unlock();
            return;
        }
        // remove temp file
        std::remove(temp_filename.c_str());

        printf("Successfully loaded %s\n", filename.c_str());

        // print system information
        {
            fprintf(stderr, "\n");
            fprintf(stderr, "system_info: n_threads = %d / %d | %s\n",
                    params.n_threads*params.n_processors, std::thread::hardware_concurrency(), whisper_print_system_info());
        }

        // print some info about the processing
        {
            fprintf(stderr, "\n");
            if (!whisper_is_multilingual(ctx)) {
                if (params.language != "en" || params.translate) {
                    params.language = "en";
                    params.translate = false;
                    fprintf(stderr, "%s: WARNING: model is not multilingual, ignoring language and translation options\n", __func__);
                }
            }
            if (params.detect_language) {
                params.language = "auto";
            }
            fprintf(stderr, "%s: processing '%s' (%d samples, %.1f sec), %d threads, %d processors, lang = %s, task = %s, %stimestamps = %d ...\n",
                    __func__, filename.c_str(), int(pcmf32.size()), float(pcmf32.size())/WHISPER_SAMPLE_RATE,
                    params.n_threads, params.n_processors,
                    params.language.c_str(),
                    params.translate ? "translate" : "transcribe",
                    params.tinydiarize ? "tdrz = 1, " : "",
                    params.no_timestamps ? 0 : 1);

            fprintf(stderr, "\n");
        }

        // run the inference
        {

            printf("Running whisper.cpp inference on %s\n", filename.c_str());
            whisper_full_params wparams = whisper_full_default_params(WHISPER_SAMPLING_GREEDY);

            wparams.strategy = params.beam_size > 1 ? WHISPER_SAMPLING_BEAM_SEARCH : WHISPER_SAMPLING_GREEDY;

            wparams.print_realtime   = false;
            wparams.print_progress   = params.print_progress;
            wparams.print_timestamps = !params.no_timestamps;
            wparams.print_special    = params.print_special;
            wparams.translate        = params.translate;
            wparams.language         = params.language.c_str();
            wparams.detect_language  = params.detect_language;
            wparams.n_threads        = params.n_threads;
            wparams.n_max_text_ctx   = params.max_context >= 0 ? params.max_context : wparams.n_max_text_ctx;
            wparams.offset_ms        = params.offset_t_ms;
            wparams.duration_ms      = params.duration_ms;

            wparams.thold_pt         = params.word_thold;
            wparams.split_on_word    = params.split_on_word;

            wparams.speed_up         = params.speed_up;
            wparams.debug_mode       = params.debug_mode;

            wparams.tdrz_enable      = params.tinydiarize; // [TDRZ]

            wparams.initial_prompt   = params.prompt.c_str();

            wparams.greedy.best_of        = params.best_of;
            wparams.beam_search.beam_size = params.beam_size;

            wparams.temperature_inc  = params.userdef_temp;
            wparams.entropy_thold    = params.entropy_thold;
            wparams.logprob_thold    = params.logprob_thold;

            whisper_print_user_data user_data = { &params, &pcmf32s, 0 };

            // this callback is called on each new segment
            if (params.print_realtime) {
                wparams.new_segment_callback           = whisper_print_segment_callback;
                wparams.new_segment_callback_user_data = &user_data;
            }

            if (wparams.print_progress) {
                wparams.progress_callback           = whisper_print_progress_callback;
                wparams.progress_callback_user_data = &user_data;
            }

            // examples for abort mechanism
            // in examples below, we do not abort the processing, but we could if the flag is set to true

            // the callback is called before every encoder run - if it returns false, the processing is aborted
            {
                static bool is_aborted = false; // NOTE: this should be atomic to avoid data race

                wparams.encoder_begin_callback = [](struct whisper_context * /*ctx*/, struct whisper_state * /*state*/, void * user_data) {
                    bool is_aborted = *(bool*)user_data;
                    return !is_aborted;
                };
                wparams.encoder_begin_callback_user_data = &is_aborted;
            }

            // the callback is called before every computation - if it returns true, the computation is aborted
            {
                static bool is_aborted = false; // NOTE: this should be atomic to avoid data race

                wparams.abort_callback = [](void * user_data) {
                    bool is_aborted = *(bool*)user_data;
                    return is_aborted;
                };
                wparams.abort_callback_user_data = &is_aborted;
            }

            if (whisper_full_parallel(ctx, wparams, pcmf32.data(), pcmf32.size(), params.n_processors) != 0) {
                fprintf(stderr, "%s: failed to process audio\n", argv[0]);
                const std::string error_resp = "{\"error\":\"failed to process audio\"}";
                res.set_content(error_resp, "application/json");
                whisper_mutex.unlock();
                return;
            }
        }

        // return results to user
        if (params.response_format == text_format)
        {
            std::string results = output_str(ctx, params, pcmf32s);
            res.set_content(results.c_str(), "text/html");
        }
        // TODO add more output formats
        else
        {
            std::string results = output_str(ctx, params, pcmf32s);
            json jres = json{
                {"text", results}
            };
            res.set_content(jres.dump(-1, ' ', false, json::error_handler_t::replace),
                            "application/json");
        }

        // return whisper model mutex lock
        whisper_mutex.unlock();
    });
    svr.Post("/load", [&](const Request &req, Response &res){
        whisper_mutex.lock();
        if (!req.has_file("model"))
        {
            fprintf(stderr, "error: no 'model' field in the request\n");
            const std::string error_resp = "{\"error\":\"no 'model' field in the request\"}";
            res.set_content(error_resp, "application/json");
            whisper_mutex.unlock();
            return;
        }
        std::string model = req.get_file_value("model").content;
        if (!is_file_exist(model.c_str()))
        {
            fprintf(stderr, "error: 'model': %s not found!\n", model.c_str());
            const std::string error_resp = "{\"error\":\"model not found!\"}";
            res.set_content(error_resp, "application/json");
            whisper_mutex.unlock();
            return;
        }

        // clean up
        whisper_free(ctx);

        // whisper init
        ctx = whisper_init_from_file_with_params(model.c_str(), cparams);

        // TODO perhaps load prior model here instead of exit
        if (ctx == nullptr) {
            fprintf(stderr, "error: model init  failed, no model loaded must exit\n");
            exit(1);
        }

        // initialize openvino encoder. this has no effect on whisper.cpp builds that don't have OpenVINO configured
        whisper_ctx_init_openvino_encoder(ctx, nullptr, params.openvino_encode_device.c_str(), nullptr);

        const std::string success = "Load was successful!";
        res.set_content(success, "application/text");

        // check if the model is in the file system
        whisper_mutex.unlock();
    });

    svr.set_exception_handler([](const Request &, Response &res, std::exception_ptr ep) {
        const char fmt[] = "500 Internal Server Error\n%s";
        char buf[BUFSIZ];
        try {
            std::rethrow_exception(std::move(ep));
        } catch (std::exception &e) {
            snprintf(buf, sizeof(buf), fmt, e.what());
        } catch (...) {
            snprintf(buf, sizeof(buf), fmt, "Unknown Exception");
        }
        res.set_content(buf, "text/plain");
        res.status = 500;
    });

    svr.set_error_handler([](const Request &, Response &res) {
        if (res.status == 400) {
            res.set_content("Invalid request", "text/plain");
        } else if (res.status != 500) {
            res.set_content("File Not Found", "text/plain");
            res.status = 404;
        }
    });

    // set timeouts and change hostname and port
    svr.set_read_timeout(sparams.read_timeout);
    svr.set_write_timeout(sparams.write_timeout);

    if (!svr.bind_to_port(sparams.hostname, sparams.port))
    {
        fprintf(stderr, "\ncouldn't bind to server socket: hostname=%s port=%d\n\n",
                sparams.hostname.c_str(), sparams.port);
        return 1;
    }

    // Set the base directory for serving static files
    svr.set_base_dir(sparams.public_path);

    // to make it ctrl+clickable:
    printf("\nwhisper server listening at http://%s:%d\n\n", sparams.hostname.c_str(), sparams.port);

    if (!svr.listen_after_bind())
    {
        return 1;
    }

    whisper_print_timings(ctx);
    whisper_free(ctx);

    return 0;
}