examples : add parakeet-server example

This commit adds a http server for parkeet similar to whisper-server.
The shared functionality has been extracted in to
examples/server-common.h to avoid code duplication.

Author: danbev

examples/CMakeLists.txt

@@ -109,6 +109,7 @@ else()
     add_subdirectory(vad-speech-segments)
     add_subdirectory(parakeet-cli)
     add_subdirectory(parakeet-quantize)
+    add_subdirectory(parakeet-server)
     if (WHISPER_SDL2)
         add_subdirectory(stream)
         add_subdirectory(command)

examples/server/httplib.h examples/httplib.hexamples/server/httplib.h renamed to examples/httplib.h

@@ -0,0 +1,17 @@
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+set(TARGET parakeet-server)
+add_executable(${TARGET} parakeet-server.cpp)
+
+include(DefaultTargetOptions)
+
+target_sources(${TARGET} PRIVATE ../server-common.cpp)
+
+target_link_libraries(${TARGET} PRIVATE common json_cpp parakeet ${CMAKE_THREAD_LIBS_INIT})
+
+if (WIN32)
+    target_link_libraries(${TARGET} PRIVATE ws2_32)
+endif()
+
+install(TARGETS ${TARGET} RUNTIME)

examples/parakeet-server/CMakeLists.txt

@@ -0,0 +1,350 @@
+#include "server-common.h"
+#include "common-whisper.h"
+
+#include <cstdio>
+#include <csignal>
+#include <random>
+#include <sstream>
+#include <memory>
+#include <fstream>
+#include <algorithm>
+#include <cmath>
+#include <cstdlib>
+#include <filesystem>
+
+#if defined (_WIN32)
+#include <windows.h>
+#endif
+
+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";
+
+namespace {
+    std::function<void()> g_shutdown_callback;
+    std::atomic_flag g_is_terminating = ATOMIC_FLAG_INIT;
+
+    void signal_handler(int /*signal*/) {
+        if (g_is_terminating.test_and_set()) {
+            fprintf(stderr, "Received second interrupt, terminating immediately.\n");
+            exit(1);
+        }
+        if (g_shutdown_callback) {
+            g_shutdown_callback();
+        }
+    }
+}
+
+bool parse_str_to_bool(const std::string & s) {
+    if (s == "true" || s == "1" || s == "yes" || s == "y") {
+        return true;
+    }
+    return false;
+}
+
+bool check_ffmpeg_availability() {
+    int result = system("ffmpeg -version");
+    if (result == 0) {
+        std::cout << "ffmpeg is available." << std::endl;
+    } else {
+        std::cout << "ffmpeg is not found. Please ensure that ffmpeg is installed "
+                  << "and that its executable is included in your system's PATH. ";
+        exit(0);
+    }
+    return true;
+}
+
+std::string generate_temp_filename(const std::string & path, const std::string & prefix, const std::string & extension) {
+    auto now = std::chrono::system_clock::now();
+    auto now_time_t = std::chrono::system_clock::to_time_t(now);
+
+    static std::mt19937 rng{std::random_device{}()};
+    std::uniform_int_distribution<long long> dist(0, 1e9);
+
+    std::stringstream ss;
+    ss << path
+       << std::filesystem::path::preferred_separator
+       << prefix
+       << "-"
+       << std::put_time(std::localtime(&now_time_t), "%Y%m%d-%H%M%S")
+       << "-"
+       << dist(rng)
+       << extension;
+
+    return ss.str();
+}
+
+bool convert_to_wav(const std::string & temp_filename, std::string & error_resp, bool stereo) {
+    std::ostringstream cmd_stream;
+    std::string converted_filename_temp = temp_filename + "_temp.wav";
+    cmd_stream << "ffmpeg -i \"" << temp_filename << "\" -y -ar 16000 -ac " << (stereo ? 2 : 1) << " -c:a pcm_s16le \"" << converted_filename_temp << "\" 2>&1";
+    std::string cmd = cmd_stream.str();
+
+    int status = std::system(cmd.c_str());
+    if (status != 0) {
+        error_resp = "{\"error\":\"FFmpeg conversion failed.\"}";
+        return false;
+    }
+
+    if (remove(temp_filename.c_str()) != 0) {
+        error_resp = "{\"error\":\"Failed to remove the original file.\"}";
+        return false;
+    }
+
+    if (rename(converted_filename_temp.c_str(), temp_filename.c_str()) != 0) {
+        error_resp = "{\"error\":\"Failed to rename the temporary file.\"}";
+        return false;
+    }
+    return true;
+}
+
+void setup_signal_handler(std::function<void()> shutdown_callback) {
+    g_shutdown_callback = std::move(shutdown_callback);
+
+#if defined (__unix__) || (defined (__APPLE__) && defined (__MACH__))
+    struct sigaction sigint_action;
+    sigint_action.sa_handler = signal_handler;
+    sigemptyset(&sigint_action.sa_mask);
+    sigint_action.sa_flags = 0;
+    sigaction(SIGINT, &sigint_action, NULL);
+    sigaction(SIGTERM, &sigint_action, NULL);
+#elif defined (_WIN32)
+    auto console_ctrl_handler = +[](DWORD ctrl_type) -> BOOL {
+        return (ctrl_type == CTRL_C_EVENT) ? (signal_handler(SIGINT), true) : false;
+    };
+    SetConsoleCtrlHandler(reinterpret_cast<PHANDLER_ROUTINE>(console_ctrl_handler), true);
+#endif
+}
+
+static std::string ms_to_timestamp(int64_t t_ms, bool comma = false) {
+    // to_timestamp expects centiseconds, our adapter uses milliseconds
+    return ::to_timestamp(t_ms / 10, comma);
+}
+
+
+std::string format_text(const transcription_result & result) {
+    std::stringstream ss;
+    const int n_segments = result.n_segments();
+    for (int i = 0; i < n_segments; ++i) {
+        auto seg = result.get_segment(i);
+        auto speaker = result.get_speaker(i);
+        ss << speaker << seg.text << "\n";
+    }
+    return ss.str();
+}
+
+std::string format_srt(const transcription_result & result, int offset_n) {
+    std::stringstream ss;
+    const int n_segments = result.n_segments();
+    for (int i = 0; i < n_segments; ++i) {
+        auto seg = result.get_segment(i);
+        auto speaker = result.get_speaker(i);
+
+        ss << i + 1 + offset_n << "\n";
+        ss << ms_to_timestamp(seg.t0, true) << " --> " << ms_to_timestamp(seg.t1, true) << "\n";
+        ss << speaker << seg.text << "\n\n";
+    }
+    return ss.str();
+}
+
+std::string format_vtt(const transcription_result & result) {
+    std::stringstream ss;
+    ss << "WEBVTT\n\n";
+
+    const int n_segments = result.n_segments();
+    for (int i = 0; i < n_segments; ++i) {
+        auto seg = result.get_segment(i);
+        std::string speaker_tag;
+
+        auto speaker_id = result.get_speaker(i);
+        if (!speaker_id.empty()) {
+            speaker_tag = "<v Speaker" + speaker_id + ">";
+        }
+
+        ss << ms_to_timestamp(seg.t0) << " --> " << ms_to_timestamp(seg.t1) << "\n";
+        ss << speaker_tag << seg.text << "\n\n";
+    }
+    return ss.str();
+}
+
+std::string format_json(const transcription_result & result) {
+    std::string text = format_text(result);
+    json jres = json{{"text", text}};
+    return jres.dump(-1, ' ', false, json::error_handler_t::replace);
+}
+
+std::string format_verbose_json(
+        const transcription_result & result,
+        float temperature,
+        float duration,
+        bool no_timestamps,
+        bool token_timestamps) {
+    std::string text = format_text(result);
+    std::string task     = result.get_task();
+    std::string language = result.get_language();
+
+    json jres = json{
+        {"task", task},
+        {"language", language},
+        {"duration", duration},
+        {"text", text},
+        {"segments", json::array()}
+    };
+
+    // Merge language probability data into the top-level response.
+    // Adapters return a json object whose keys are merged directly, allowing
+    // model-specific fields (e.g. whisper's detected_language) to appear at
+    // the top level alongside the standard language_probabilities map.
+    json lang_data = result.get_language_probabilities();
+    for (auto & [key, val] : lang_data.items()) {
+        jres[key] = val;
+    }
+
+    const int n_segments = result.n_segments();
+    for (int i = 0; i < n_segments; ++i) {
+        auto seg = result.get_segment(i);
+
+        json segment = json{
+            {"id", i},
+            {"text", seg.text},
+        };
+
+        if (!no_timestamps) {
+            segment["start"] = seg.t0 * 0.001f;  // ms -> seconds
+            segment["end"] = seg.t1 * 0.001f;
+        }
+
+        auto speaker_id = result.get_speaker(i);
+        if (!speaker_id.empty()) {
+            segment["speaker"] = speaker_id;
+        }
+
+        // Build word-level tokens by merging partial UTF-8 tokens
+        std::vector<json> words;
+        int n_tokens = (int)seg.tokens.size();
+        float total_logprob = 0.0f;
+
+        for (int j = 0; j < n_tokens; ++j) {
+            auto & tok = seg.tokens[j];
+
+            // Merge trailing partial UTF-8 bytes into complete words
+            std::string word_text = tok.text;
+            int64_t word_t1 = tok.t1;
+
+            while (j + 1 < n_tokens) {
+                int trailing = utf8_trailing_bytes_needed(word_text);
+                if (trailing <= 0) break;
+
+                ++j;
+                auto & next_tok = seg.tokens[j];
+                word_text += next_tok.text;
+                if (next_tok.t1 > word_t1) {
+                    word_t1 = next_tok.t1;
+                }
+            }
+
+            json word = json{{"word", word_text}};
+            if (!no_timestamps && token_timestamps) {
+                word["start"] = tok.t0 * 0.001f;
+                word["end"] = word_t1 * 0.001f;
+            }
+            word["probability"] = tok.prob;
+
+            // Approximate logprob from probability
+            float logprob = tok.prob > 0.0f ? std::log(tok.prob + 1e-10f) : -1e10f;
+            total_logprob += logprob;
+
+            words.push_back(word);
+        }
+
+        segment["words"] = words;
+        segment["tokens"] = json::array();
+        for (auto & tok : seg.tokens) {
+            segment["tokens"].push_back(tok.id);
+        }
+
+        segment["temperature"] = temperature;
+        int n_word_tokens = (int)seg.tokens.size();
+        segment["avg_logprob"] = n_word_tokens > 0 ? total_logprob / n_word_tokens : 0.0f;
+        segment["no_speech_prob"] = seg.no_speech_prob;
+
+        jres["segments"].push_back(segment);
+    }
+
+    return jres.dump(-1, ' ', false, json::error_handler_t::replace);
+}
+
+void setup_server_common(
+        httplib::Server & svr,
+        const server_params & sparams,
+        std::atomic<server_state> & state,
+        std::function<void(const httplib::Request &, httplib::Response &)> load_handler,
+        std::function<void(const httplib::Request &, httplib::Response &)> inference_handler,
+        const std::string & default_content,
+        const std::string & server_name) {
+
+    svr.set_default_headers({
+        {"Server", server_name},
+        {"Access-Control-Allow-Origin", "*"},
+        {"Access-Control-Allow-Headers", "content-type, authorization"}
+    });
+
+    // Default index page
+    svr.Get(sparams.request_path + "/", [&](const httplib::Request &, httplib::Response & res) {
+        res.set_content(default_content, "text/html");
+        return false;
+    });
+
+    // CORS preflight
+    svr.Options(sparams.request_path + sparams.inference_path,
+                [&](const httplib::Request &, httplib::Response &) {});
+
+    // Inference endpoint
+    svr.Post(sparams.request_path + sparams.inference_path, inference_handler);
+
+    // Model reload endpoint
+    if (load_handler) {
+        svr.Post(sparams.request_path + "/load", load_handler);
+    }
+
+    // Health check
+    svr.Get(sparams.request_path + "/health", [&](const httplib::Request &, httplib::Response & res) {
+        server_state current_state = state.load();
+        if (current_state == SERVER_STATE_READY) {
+            res.set_content("{\"status\":\"ok\"}", "application/json");
+        } else {
+            res.set_content("{\"status\":\"loading model\"}", "application/json");
+            res.status = 503;
+        }
+    });
+
+    // Exception handler
+    svr.set_exception_handler([](const httplib::Request &, httplib::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;
+    });
+
+    // Error handler
+    svr.set_error_handler([](const httplib::Request & req, httplib::Response & res) {
+        if (res.status == 400) {
+            res.set_content("Invalid request", "text/plain");
+        } else if (res.status != 500) {
+            res.set_content("File Not Found (" + req.path + ")", "text/plain");
+            res.status = 404;
+        }
+    });
+
+    svr.set_read_timeout(sparams.read_timeout);
+    svr.set_write_timeout(sparams.write_timeout);
+}