Step 7.5b3b: Spotify audio on AES67

- spotify_init(pcm_cb, event_cb): cspot's data callback hands 44.1 kHz
  stereo s16 PCM to the player and returns what was taken; the player's
  blocking ring write paces decoding to playback speed.
- Events: FLUSH/SEEK/PLAYBACK_START empty the ring (skip/seek sound at
  once); PLAY_PAUSE pauses output (silence, buffer kept, no underrun);
  VOLUME logged (applied in b4).
- player: Spotify via its own audio_out converter (44.1 -> 48 kHz);
  source_state playing / paused / buffering.
- Verified from a Mac: music on the AES67 stream (10 s: 0 gaps, no
  silent packets, RMS -9.6 dBFS, peak 0.0 dBFS), buffer 4.0 s full,
  0 underruns, pause/play/skip/seek events.
  Seen: first 3 connects "Can't connect to spotify servers", 4th worked.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "external/cspot"]
+	path = external/cspot
+	url = https://github.com/philippe44/cspot.git

CLAUDE.md

@@ -27,6 +27,7 @@ Repo: https://gitea.apointless.space/bsncubed/aes67-ESP32-P4
   - Our board: **32 MB** flash (GigaDevice c8/4019). App slots must stay below 16 MB (cache mapping above 16 MB is experimental in IDF).
   - Rev < 3 also limits Espressif's prebuilt audio libraries: `esp_audio_codec` must stay < 2.6 and `esp_audio_effects` < 1.4 (newer versions use P4 assembly that needs rev >= 3; the build fails with a message saying so). Check this for any new Espressif binary component.
 - Embed `web/index.html` via `EMBED_TXTFILES` in `aes67_web`.
+- cspot (Spotify, `external/cspot` git submodule, philippe44 fork, pinned): after cloning run `git submodule update --init external/cspot && git -C external/cspot submodule update --init cspot/bell`. Its nanopb code generator needs, in the IDF Python env: `python -m pip install protobuf grpcio-tools 'setuptools<81'` (after `. export.sh`). Our fixes to cspot/bell live in `components/spotify/patches/{cspot,bell}/*.patch` and are applied automatically at configure time; don't edit the submodule directly, add a patch.
 - Flash over the network (normal way since step 2b; keep USB for recovery):
   `curl -f --data-binary @build/aes67_p4.bin -H 'Content-Type: application/octet-stream' http://p4-aes67/api/ota`
   The board reboots into the new image on trial; check `GET /api/ota` shows the new version with `pending_verify: false`.

components/aes67_web/cfg.c

@@ -13,6 +13,7 @@
 #include "nvs_flash.h"
 
 #define MAX_GROUPS      12
+#define MAX_SECRETS     4
 #define MAX_BODY        8192
 #define NVS_NAMESPACE   "cfg"
 
@@ -24,6 +25,8 @@ typedef struct {
     cJSON *values;
     cfg_validate_cb_t validate;
     cfg_apply_cb_t apply;
+    char secrets[MAX_SECRETS][24];  // write-only keys
+    int n_secrets;
 } cfg_group_t;
 
 static cfg_group_t s_groups[MAX_GROUPS];
@@ -220,6 +223,35 @@ esp_err_t cfg_register(const char *group, const char *defaults_json,
     return ESP_OK;
 }
 
+esp_err_t cfg_mark_secret(const char *group, const char *key)
+{
+    if (!s_lock) {
+        return ESP_ERR_INVALID_STATE;
+    }
+    xSemaphoreTake(s_lock, portMAX_DELAY);
+    cfg_group_t *g = find(group);
+    esp_err_t err = ESP_OK;
+    if (!g || !cJSON_IsString(cJSON_GetObjectItemCaseSensitive(g->defaults, key))) {
+        err = ESP_ERR_NOT_FOUND;
+    } else if (g->n_secrets >= MAX_SECRETS || strlen(key) >= sizeof(g->secrets[0])) {
+        err = ESP_ERR_NO_MEM;
+    } else {
+        strcpy(g->secrets[g->n_secrets++], key);
+    }
+    xSemaphoreGive(s_lock);
+    return err;
+}
+
+// Group values for the API: secrets blanked.
+static cJSON *public_values(const cfg_group_t *g)
+{
+    cJSON *v = cJSON_Duplicate(g->values, true);
+    for (int i = 0; i < g->n_secrets; i++) {
+        cJSON_ReplaceItemInObjectCaseSensitive(v, g->secrets[i], cJSON_CreateString(""));
+    }
+    return v;
+}
+
 cJSON *cfg_get(const char *group)
 {
     if (!s_lock) {
@@ -270,7 +302,7 @@ static esp_err_t config_get(httpd_req_t *req)
     cJSON *all = cJSON_CreateObject();
     xSemaphoreTake(s_lock, portMAX_DELAY);
     for (int i = 0; i < s_group_n; i++) {
-        cJSON_AddItemToObject(all, s_groups[i].name, cJSON_Duplicate(s_groups[i].values, true));
+        cJSON_AddItemToObject(all, s_groups[i].name, public_values(&s_groups[i]));
     }
     xSemaphoreGive(s_lock);
     esp_err_t err = web_send_json(req, all);
@@ -331,7 +363,18 @@ static esp_err_t config_post(httpd_req_t *req)
             break;
         }
         cand[i] = cJSON_Duplicate(g->values, true);
-        ok = merge_known(cand[i], g->defaults, src, g->name, err, sizeof(err));
+        // Secrets: "" = unchanged (the API never returns the stored value), null = clear.
+        cJSON *in_g = cJSON_Duplicate(src, true);
+        for (int k = 0; k < g->n_secrets; k++) {
+            const cJSON *sv = cJSON_GetObjectItemCaseSensitive(in_g, g->secrets[k]);
+            if (cJSON_IsString(sv) && !sv->valuestring[0]) {
+                cJSON_DeleteItemFromObjectCaseSensitive(in_g, g->secrets[k]);
+            } else if (cJSON_IsNull(sv)) {
+                cJSON_ReplaceItemInObjectCaseSensitive(in_g, g->secrets[k], cJSON_CreateString(""));
+            }
+        }
+        ok = merge_known(cand[i], g->defaults, in_g, g->name, err, sizeof(err));
+        cJSON_Delete(in_g);
         if (ok && g->validate) {
             char verr[96] = "";
             ok = g->validate(cand[i], verr, sizeof(verr));

components/aes67_web/include/aes67_cfg.h

@@ -18,6 +18,9 @@ esp_err_t cfg_override_defaults(const char *group, const char *json);
 // Register a group. Stored values (NVS) are loaded immediately, merged over the defaults.
 esp_err_t cfg_register(const char *group, const char *defaults_json,
                        cfg_validate_cb_t validate, cfg_apply_cb_t apply);
+// Write-only key (e.g. a password): GET /api/config returns "" for it; a POST with "" keeps the
+// stored value, null clears it. cfg_get() still returns the real value. Call after cfg_register().
+esp_err_t cfg_mark_secret(const char *group, const char *key);
 // Copy of a group's current values; caller frees with cJSON_Delete. NULL if not registered.
 cJSON *cfg_get(const char *group);
 // Firmware-side change of one number (e.g. aes67.session_ver): stored like a POST, no validation.

components/spotify/CMakeLists.txt

@@ -0,0 +1,49 @@
+# Spotify Connect via cspot (philippe44 fork, git submodule external/cspot). GPL-3.0.
+# Project component (not part of the reusable aes67_* core).
+idf_component_register(SRCS "spotify.cpp"
+                       INCLUDE_DIRS "include"
+                       PRIV_REQUIRES aes67_web espressif__mdns mbedtls json pthread lwip esp_timer esp_http_server)
+
+# bell: only what cspot needs (Tremor Vorbis inside; no codec wrapper, sinks, MQTT, web server).
+set(BELL_DISABLE_CODECS ON CACHE BOOL "" FORCE)
+set(BELL_DISABLE_SINKS ON CACHE BOOL "" FORCE)
+set(BELL_DISABLE_MQTT ON CACHE BOOL "" FORCE)
+set(BELL_DISABLE_WEBSERVER ON CACHE BOOL "" FORCE)
+set(BELL_DISABLE_FMT ON CACHE BOOL "" FORCE)
+set(BELL_DISABLE_REGEX ON CACHE BOOL "" FORCE)
+set(BELL_ONLY_CJSON ON CACHE BOOL "" FORCE)
+set(BELL_EXTERNAL_CJSON idf::json CACHE STRING "" FORCE)
+option(BUILD_TESTING OFF)
+
+# Our fixes to the pinned cspot / bell sources (newer GCC, protobuf, CMake), kept as patch files:
+# patches/cspot/*.patch apply in external/cspot, patches/bell/*.patch in external/cspot/cspot/bell.
+# Each is applied once (skipped when it already reverse-applies).
+function(spotify_apply_patches dir repo)
+    file(GLOB patches "${CMAKE_CURRENT_LIST_DIR}/patches/${dir}/*.patch")
+    list(SORT patches)
+    foreach(p ${patches})
+        execute_process(COMMAND git apply --reverse --check "${p}" WORKING_DIRECTORY "${repo}"
+                        RESULT_VARIABLE applied OUTPUT_QUIET ERROR_QUIET)
+        if(NOT applied EQUAL 0)
+            execute_process(COMMAND git apply "${p}" WORKING_DIRECTORY "${repo}" RESULT_VARIABLE rc)
+            if(NOT rc EQUAL 0)
+                message(FATAL_ERROR "spotify: patch does not apply: ${p}")
+            endif()
+            message(STATUS "spotify: applied ${p}")
+        endif()
+    endforeach()
+endfunction()
+spotify_apply_patches(cspot "${PROJECT_DIR}/external/cspot")
+spotify_apply_patches(bell "${PROJECT_DIR}/external/cspot/cspot/bell")
+
+# cspot/bell declare cmake_minimum_required(2.8.12); CMake 4 rejects < 3.5 unless told otherwise.
+set(CMAKE_POLICY_VERSION_MINIMUM 3.5)
+add_subdirectory(${PROJECT_DIR}/external/cspot/cspot ${CMAKE_CURRENT_BINARY_DIR}/cspot)
+
+# bell adds Xtensa (ESP32) assembly for a DSP biquad; the P4 is RISC-V and cspot does not use it.
+get_target_property(BELL_SRCS bell SOURCES)
+list(FILTER BELL_SRCS EXCLUDE REGEX "\\.S$")
+set_target_properties(bell PROPERTIES SOURCES "${BELL_SRCS}")
+
+target_link_libraries(${COMPONENT_LIB} PRIVATE cspot)
+target_compile_options(${COMPONENT_LIB} PRIVATE -std=gnu++20)

components/spotify/include/spotify.h

@@ -0,0 +1,32 @@
+// Spotify Connect (cspot). Project code; GPL-3.0 through cspot.
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "esp_err.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef enum {
+    SPOTIFY_EV_PLAY,        // playback (re)started or resumed
+    SPOTIFY_EV_PAUSE,
+    SPOTIFY_EV_FLUSH,       // skip, seek, new track: drop buffered audio
+    SPOTIFY_EV_VOLUME,      // value: 0..65535
+} spotify_event_t;
+
+// PCM from Spotify: 44.1 kHz stereo s16 interleaved. Return the frames taken (may block).
+typedef size_t (*spotify_pcm_cb_t)(const int16_t *pcm, size_t frames);
+typedef void (*spotify_event_cb_t)(spotify_event_t ev, int value);
+
+// Registers the zeroconf endpoints (/spotify_info) and, when source.mode is spotify/auto and the
+// client credentials are set, advertises the device and starts the session task.
+esp_err_t spotify_init(spotify_pcm_cb_t pcm, spotify_event_cb_t event);
+// Current state for status.spotify_state.
+const char *spotify_state(void);
+
+#ifdef __cplusplus
+}
+#endif

components/spotify/patches/bell/0001-nanopb-generator-protobuf5.patch

@@ -0,0 +1,18 @@
+diff --git a/external/nanopb/generator/nanopb_generator.py b/external/nanopb/generator/nanopb_generator.py
+index e40f18b..64dad5e 100755
+--- a/external/nanopb/generator/nanopb_generator.py
++++ b/external/nanopb/generator/nanopb_generator.py
+@@ -1463,7 +1463,12 @@ class Message(ProtoElement):
+         optional_only.ClearField(str('extension'))
+         optional_only.ClearField(str('enum_type'))
+         desc = google.protobuf.descriptor.MakeDescriptor(optional_only)
+-        msg = reflection.MakeClass(desc)()
++        # protobuf >= 5 removed reflection.MakeClass (patch for this project)
++        try:
++            msg = reflection.MakeClass(desc)()
++        except AttributeError:
++            from google.protobuf import message_factory
++            msg = message_factory.GetMessageClass(desc)()
+ 
+         for field in optional_only.field:
+             if field.type == FieldD.TYPE_STRING:

components/spotify/patches/bell/0002-urlparser-includes.patch

@@ -0,0 +1,13 @@
+diff --git a/main/io/URLParser.cpp b/main/io/URLParser.cpp
+index 4a50ab1..af679ec 100644
+--- a/main/io/URLParser.cpp
++++ b/main/io/URLParser.cpp
+@@ -1,5 +1,8 @@
+ #include "URLParser.h"
+ 
++#include <cstdio>   // sscanf (GCC 14 / ESP-IDF 5.5: not included transitively)
++#include <cstring>  // strstr
++
+ namespace bell {
+ 
+ #ifdef BELL_DISABLE_REGEX

components/spotify/spotify.cpp

@@ -0,0 +1,285 @@
+#include "spotify.h"
+
+#include <atomic>
+#include <cstring>
+#include <exception>
+#include <map>
+#include <memory>
+#include <string>
+
+#include "BellLogger.h"
+#include "CSpotContext.h"
+#include "LoginBlob.h"
+#include "SpircHandler.h"
+#include "TrackPlayer.h"
+#include "esp_log.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "mdns.h"
+
+extern "C" {
+#include "aes67_cfg.h"
+#include "aes67_web.h"
+}
+
+#define BODY_MAX 8192
+
+static const char *TAG = "spotify";
+
+static std::shared_ptr<cspot::LoginBlob> s_blob;
+static std::atomic<bool> s_got_blob{false};
+static std::atomic<const char *> s_state{"disabled"};
+static std::atomic<uint64_t> s_pcm_bytes{0};
+static spotify_pcm_cb_t s_pcm_cb;
+static spotify_event_cb_t s_event_cb;
+
+const char *spotify_state(void)
+{
+    return s_state.load();
+}
+
+/* ----- cspot/bell logging -> esp_log (UART + syslog) ----- */
+
+// cspot logs through bell::bellGlobalLogger; without one, CSPOT_LOG dereferences NULL.
+class EspLogger : public bell::AbstractLogger {
+    static void out(esp_log_level_t lvl, const std::string &file, int line, const std::string &sub,
+                    const char *fmt, va_list ap)
+    {
+        char msg[256];
+        vsnprintf(msg, sizeof(msg), fmt, ap);
+        // CDN URLs carry signed tokens: keep them out of the log (syslog may leave the box).
+        char *q = strstr(msg, "?__token__=");
+        if (q) {
+            strcpy(q, "?__token__=...");
+        }
+        size_t slash = file.find_last_of('/');
+        const char *base = file.c_str() + (slash == std::string::npos ? 0 : slash + 1);
+        ESP_LOG_LEVEL(lvl, sub.empty() ? "cspot" : sub.c_str(), "%s:%d: %s", base, line, msg);
+    }
+
+public:
+    void debug(std::string file, int line, std::string sub, const char *fmt, ...) override
+    {
+        va_list ap;
+        va_start(ap, fmt);
+        out(ESP_LOG_DEBUG, file, line, sub, fmt, ap);
+        va_end(ap);
+    }
+    void info(std::string file, int line, std::string sub, const char *fmt, ...) override
+    {
+        va_list ap;
+        va_start(ap, fmt);
+        out(ESP_LOG_INFO, file, line, sub, fmt, ap);
+        va_end(ap);
+    }
+    void error(std::string file, int line, std::string sub, const char *fmt, ...) override
+    {
+        va_list ap;
+        va_start(ap, fmt);
+        out(ESP_LOG_ERROR, file, line, sub, fmt, ap);
+        va_end(ap);
+    }
+};
+
+/* ----- zeroconf (Spotify Connect discovery) on our httpd ----- */
+
+static esp_err_t info_get(httpd_req_t *req)
+{
+    std::string json = s_blob->buildZeroconfInfo();
+    httpd_resp_set_type(req, "application/json");
+    return httpd_resp_send(req, json.data(), json.size());
+}
+
+static std::string url_decode(const char *s, size_t n)
+{
+    std::string out;
+    for (size_t i = 0; i < n; i++) {
+        if (s[i] == '+') {
+            out += ' ';
+        } else if (s[i] == '%' && i + 2 < n && isxdigit((unsigned char)s[i + 1]) && isxdigit((unsigned char)s[i + 2])) {
+            char hex[3] = { s[i + 1], s[i + 2], 0 };
+            out += (char)strtol(hex, nullptr, 16);
+            i += 2;
+        } else {
+            out += s[i];
+        }
+    }
+    return out;
+}
+
+// The Spotify app posts its login blob (action=addUser&userName=...&blob=...&clientKey=...).
+static esp_err_t info_post(httpd_req_t *req)
+{
+    if (req->content_len == 0 || req->content_len > BODY_MAX) {
+        return httpd_resp_send_err(req, HTTPD_400_BAD_REQUEST, "bad body");
+    }
+    std::string body(req->content_len, '\0');
+    size_t got = 0;
+    while (got < body.size()) {
+        int r = httpd_req_recv(req, body.data() + got, body.size() - got);
+        if (r <= 0) {
+            return ESP_FAIL;
+        }
+        got += r;
+    }
+    std::map<std::string, std::string> query;
+    size_t pos = 0;
+    while (pos < body.size()) {
+        size_t amp = body.find('&', pos), end = amp == std::string::npos ? body.size() : amp;
+        size_t eq = body.find('=', pos);
+        if (eq != std::string::npos && eq < end) {
+            query[url_decode(&body[pos], eq - pos)] = url_decode(&body[eq + 1], end - eq - 1);
+        }
+        pos = end + 1;
+    }
+    ESP_LOGI(TAG, "zeroconf %s from \"%s\"", query["action"].c_str(), query["userName"].c_str());
+    s_blob->loadZeroconfQuery(query);
+    s_got_blob = true;
+    static const char ok[] = "{\"status\":101,\"spotifyError\":0,\"statusString\":\"ERROR-OK\"}";
+    httpd_resp_set_type(req, "application/json");
+    return httpd_resp_send(req, ok, sizeof(ok) - 1);
+}
+
+/* ----- session ----- */
+
+static const char *event_name(cspot::SpircHandler::EventType t)
+{
+    using E = cspot::SpircHandler::EventType;
+    switch (t) {
+    case E::PLAY_PAUSE: return "PLAY_PAUSE";
+    case E::VOLUME: return "VOLUME";
+    case E::TRACK_INFO: return "TRACK_INFO";
+    case E::DISC: return "DISC";
+    case E::NEXT: return "NEXT";
+    case E::PREV: return "PREV";
+    case E::SEEK: return "SEEK";
+    case E::DEPLETED: return "DEPLETED";
+    case E::FLUSH: return "FLUSH";
+    case E::PLAYBACK_START: return "PLAYBACK_START";
+    }
+    return "?";
+}
+
+static void session(void)
+{
+    cJSON *src = cfg_get("source");
+    std::string client_id = cJSON_GetObjectItemCaseSensitive(src, "spotify_client_id")->valuestring;
+    std::string client_secret = cJSON_GetObjectItemCaseSensitive(src, "spotify_client_secret")->valuestring;
+    int bitrate = (int)cJSON_GetObjectItemCaseSensitive(src, "spotify_bitrate")->valuedouble;
+    cJSON_Delete(src);
+
+    auto ctx = cspot::Context::createFromBlob(s_blob);
+    ctx->config.clientId = client_id;
+    ctx->config.clientSecret = client_secret;
+    ctx->config.audioFormat = bitrate >= 320 ? AudioFormat_OGG_VORBIS_320
+                              : bitrate >= 160 ? AudioFormat_OGG_VORBIS_160 : AudioFormat_OGG_VORBIS_96;
+    s_state = "connecting";
+    ctx->session->connectWithRandomAp();
+    auto token = ctx->session->authenticate(s_blob);
+    if (token.empty()) {
+        s_state = "login failed";
+        ESP_LOGE(TAG, "login failed (check the client ID/secret and that the account is Premium)");
+        return;
+    }
+    ctx->session->startTask();
+    auto handler = std::make_shared<cspot::SpircHandler>(ctx);
+    handler->subscribeToMercury();
+    // PCM (44.1 kHz stereo s16) to the player; returning fewer bytes makes cspot retry the rest,
+    // so the player's blocking write paces decoding to playback speed.
+    handler->getTrackPlayer()->setDataCallback([](uint8_t *data, size_t len, std::string_view id) -> size_t {
+        size_t frames = len / 4;
+        size_t taken = s_pcm_cb ? s_pcm_cb(reinterpret_cast<const int16_t *>(data), frames) : frames;
+        s_pcm_bytes += taken * 4;
+        return taken * 4;
+    });
+    handler->setEventHandler([](std::unique_ptr<cspot::SpircHandler::Event> ev) {
+        using E = cspot::SpircHandler::EventType;
+        switch (ev->eventType) {
+        case E::TRACK_INFO: {
+            auto &ti = std::get<cspot::TrackInfo>(ev->data);
+            ESP_LOGI(TAG, "track: %s - %s (%lu ms)", ti.artist.c_str(), ti.name.c_str(), (unsigned long)ti.duration);
+            return;
+        }
+        case E::PLAY_PAUSE:
+            if (s_event_cb) {
+                s_event_cb(std::get<bool>(ev->data) ? SPOTIFY_EV_PAUSE : SPOTIFY_EV_PLAY, 0);
+            }
+            break;
+        case E::FLUSH:
+        case E::SEEK:
+        case E::PLAYBACK_START:
+            if (s_event_cb) {
+                s_event_cb(SPOTIFY_EV_FLUSH, 0);
+                if (ev->eventType == E::PLAYBACK_START) {
+                    s_event_cb(SPOTIFY_EV_PLAY, 0);
+                }
+            }
+            break;
+        case E::VOLUME:
+            if (s_event_cb) {
+                s_event_cb(SPOTIFY_EV_VOLUME, std::get<int>(ev->data));
+            }
+            break;
+        default:
+            break;
+        }
+        ESP_LOGI(TAG, "event %s", event_name(ev->eventType));
+    });
+    s_state = "connected";
+    ESP_LOGI(TAG, "connected as %s", ctx->config.username.c_str());
+    while (true) {
+        ctx->session->handlePacket();
+    }
+}
+
+static void spotify_task(void *arg)
+{
+    while (true) {
+        s_state = "waiting for Spotify app";
+        while (!s_got_blob) {
+            vTaskDelay(pdMS_TO_TICKS(500));
+        }
+        s_got_blob = false;
+        try {
+            session();
+        } catch (const std::exception &e) {
+            s_state = "error";
+            ESP_LOGE(TAG, "session ended: %s", e.what());
+        }
+        vTaskDelay(pdMS_TO_TICKS(2000));
+    }
+}
+
+extern "C" esp_err_t spotify_init(spotify_pcm_cb_t pcm, spotify_event_cb_t event)
+{
+    s_pcm_cb = pcm;
+    s_event_cb = event;
+    if (!bell::bellGlobalLogger) {
+        bell::bellGlobalLogger = new EspLogger();
+    }
+    cJSON *src = cfg_get("source");
+    std::string mode = cJSON_GetObjectItemCaseSensitive(src, "mode")->valuestring;
+    std::string name = cJSON_GetObjectItemCaseSensitive(src, "spotify_name")->valuestring;
+    bool creds = cJSON_GetObjectItemCaseSensitive(src, "spotify_client_id")->valuestring[0] &&
+                 cJSON_GetObjectItemCaseSensitive(src, "spotify_client_secret")->valuestring[0];
+    cJSON_Delete(src);
+
+    if (mode != "spotify" && mode != "auto") {
+        s_state = "disabled (source mode)";
+        return ESP_OK;
+    }
+    if (!creds) {
+        s_state = "no client credentials";
+        ESP_LOGW(TAG, "not started: set the Spotify client ID and secret (web UI, Source)");
+        return ESP_OK;
+    }
+    s_blob = std::make_shared<cspot::LoginBlob>(name);
+    static const httpd_uri_t get = { .uri = "/spotify_info", .method = HTTP_GET, .handler = info_get, .user_ctx = nullptr };
+    static const httpd_uri_t post = { .uri = "/spotify_info", .method = HTTP_POST, .handler = info_post, .user_ctx = nullptr };
+    web_register_uri(&get);
+    web_register_uri(&post);
+    mdns_txt_item_t txt[] = { { "VERSION", "1.0" }, { "CPath", "/spotify_info" }, { "Stack", "SP" } };
+    esp_err_t err = mdns_service_add(name.c_str(), "_spotify-connect", "_tcp", 80, txt, 3);
+    ESP_LOGI(TAG, "Spotify Connect \"%s\" advertised (%s)", name.c_str(), esp_err_to_name(err));
+    return xTaskCreate(spotify_task, "spotify", 32 * 1024, nullptr, 5, nullptr) == pdPASS ? ESP_OK : ESP_ERR_NO_MEM;
+}

docs/aes67-core-base.md

@@ -25,6 +25,7 @@ Reference devices for UI and defaults: Riedel Bolero (PTP status), Riedel Direct
 
 ## Core API
 - GET/POST /api/config (full JSON; POST validates, stores to NVS, applies live where possible, returns 4xx with message on bad values)
+  - Write-only keys (`cfg_mark_secret`, e.g. passwords/client secrets): GET returns "" for them; a POST with "" keeps the stored value, null clears it. Stored in NVS in plain text (NVS encryption is not enabled).
 - GET /api/status -> {model?, fw?, power?, ip, aes67_ip, inet_ip, inet_vlan, mac, link, tx_packets, underruns, uptime_s, heap_free, psram_free, temps:[…], ptp:{…}, …project fields}
   - model, fw, power are optional; rows only appear when present (power e.g. "PoE" / "USB" if the board can detect it).
 - GET /stream.sdp, POST /api/reboot, POST /api/log/test

docs/hardware-and-design-notes.md

@@ -30,7 +30,8 @@ source (cspot Spotify Connect | HLS player) -> decode (Vorbis/AAC/MP3) -> SRC 44
 - Firmware needs Spotify events: cspot connect, disconnect, play, pause.
 
 ## Project config group
-- source: {mode: spotify|hls|auto|tone|off, spotify_name, spotify_bitrate, hls_url, autoplay, gain_db, failover_delay_s, failover_on_pause}
+- source: {mode: spotify|hls|auto|tone|off, spotify_name, spotify_bitrate, hls_url, autoplay, gain_db, failover_delay_s, failover_on_pause, spotify_client_id, spotify_client_secret}
+- spotify_client_id / spotify_client_secret: each user's own Spotify developer app (developer.spotify.com, Premium account), needed by the maintained cspot fork (philippe44/cspot) since Spotify's 2025 API restrictions. The secret is write-only (never returned by GET /api/config). spotify_state reports "no client credentials" while either is missing.
 - Project status fields: active_source, source_state, spotify_state, buffer_ms
 - mode "tone": the core's 1 kHz / -18 dBFS test tone, phase-locked to PTP (commissioning, e.g. Riedel import tests). "off": silence.
 

main/CMakeLists.txt

@@ -1,5 +1,5 @@
-idf_component_register(SRCS "main.c" "project_cfg.c" "player.c" "audio_ring.c" "hls.c" "decoder.c"
+idf_component_register(SRCS "main.c" "project_cfg.c" "player.c" "audio_ring.c" "hls.c" "decoder.c" "audio_out.c"
                        INCLUDE_DIRS "."
                        REQUIRES esp_app_format esp_hw_support heap esp_http_client mbedtls esp_timer
                                 aes67_board aes67_health aes67_net aes67_ota aes67_ptp aes67_sdp_sap
-                                aes67_syslog aes67_tx aes67_web)
+                                aes67_syslog aes67_tx aes67_web spotify)

main/audio_out.c

@@ -0,0 +1,90 @@
+#include "audio_out.h"
+
+#include <stdlib.h>
+
+#include "esp_ae_rate_cvt.h"
+#include "esp_heap_caps.h"
+#include "esp_log.h"
+
+#define OUT_RATE        48000
+#define CONV_FRAMES     4096            // per rate converter call
+
+static const char *TAG = "audio_out";
+
+struct audio_conv {
+    player_src_t src;
+    const char *name;
+    esp_ae_rate_cvt_handle_t cvt;       // NULL: no conversion (source is 48 kHz)
+    uint32_t rate;                      // input rate the converter was opened for
+    int32_t *in32, *out32;              // stereo int32 work buffers (PSRAM)
+};
+
+audio_conv_t *audio_conv_create(player_src_t src, const char *name)
+{
+    audio_conv_t *c = calloc(1, sizeof(*c));
+    if (!c) {
+        return NULL;
+    }
+    c->src = src;
+    c->name = name;
+    c->in32 = heap_caps_malloc(CONV_FRAMES * 2 * sizeof(int32_t), MALLOC_CAP_SPIRAM);
+    c->out32 = heap_caps_malloc(CONV_FRAMES * 2 * 2 * sizeof(int32_t), MALLOC_CAP_SPIRAM);
+    if (!c->in32 || !c->out32) {
+        free(c->in32);
+        free(c->out32);
+        free(c);
+        return NULL;
+    }
+    return c;
+}
+
+static void set_rate(audio_conv_t *c, uint32_t rate)
+{
+    if (c->cvt) {
+        esp_ae_rate_cvt_close(c->cvt);
+        c->cvt = NULL;
+    }
+    c->rate = rate;
+    if (rate == OUT_RATE) {
+        return;
+    }
+    esp_ae_rate_cvt_cfg_t cfg = {
+        .src_rate = rate, .dest_rate = OUT_RATE, .channel = 2, .bits_per_sample = 32,
+        .complexity = 3, .perf_type = ESP_AE_RATE_CVT_PERF_TYPE_SPEED,
+    };
+    if (esp_ae_rate_cvt_open(&cfg, &c->cvt) != ESP_AE_ERR_OK) {
+        ESP_LOGE(TAG, "%s: rate converter %lu -> %d Hz: open failed", c->name, (unsigned long)rate, OUT_RATE);
+    } else {
+        ESP_LOGI(TAG, "%s: rate converter %lu -> %d Hz", c->name, (unsigned long)rate, OUT_RATE);
+    }
+}
+
+size_t audio_conv_write(audio_conv_t *c, const int16_t *pcm, uint32_t frames, int ch, uint32_t rate)
+{
+    if (rate != c->rate) {
+        set_rate(c, rate);
+    }
+    size_t produced = 0;
+    while (frames) {
+        uint32_t n = frames < CONV_FRAMES ? frames : CONV_FRAMES;
+        for (uint32_t i = 0; i < n; i++) {      // to stereo int32 (full scale = INT32_MAX)
+            int32_t l = (int32_t)pcm[i * ch] << 16;
+            c->in32[i * 2] = l;
+            c->in32[i * 2 + 1] = ch > 1 ? (int32_t)pcm[i * ch + 1] << 16 : l;
+        }
+        const int32_t *out = c->in32;
+        uint32_t out_n = n;
+        if (c->cvt) {
+            out_n = CONV_FRAMES * 2;
+            if (esp_ae_rate_cvt_process(c->cvt, c->in32, n, c->out32, &out_n) != ESP_AE_ERR_OK) {
+                ESP_LOGW(TAG, "%s: rate conversion failed", c->name);
+                return produced;
+            }
+            out = c->out32;
+        }
+        produced += player_write(c->src, out, out_n);
+        pcm += n * ch;
+        frames -= n;
+    }
+    return produced;
+}

main/audio_out.h

@@ -0,0 +1,15 @@
+// PCM from a source (s16, any rate/channels) -> 48 kHz stereo int32 -> player ring.
+// One converter per source: each keeps its own resampler state.
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "player.h"
+
+typedef struct audio_conv audio_conv_t;
+
+audio_conv_t *audio_conv_create(player_src_t src, const char *name);
+// Blocks while the ring is full; dropped when src is not the active source.
+// Returns the 48 kHz frames produced.
+size_t audio_conv_write(audio_conv_t *c, const int16_t *pcm, uint32_t frames, int channels, uint32_t rate);

main/decoder.c

@@ -6,19 +6,15 @@
 #include "esp_audio_dec_default.h"
 #include "esp_audio_simple_dec.h"
 #include "esp_audio_simple_dec_default.h"
-#include "esp_ae_rate_cvt.h"
+#include "audio_out.h"
-#include "player.h"
 #include "esp_heap_caps.h"
 #include "esp_log.h"
 
 static const char *TAG = "decoder";
 
 #define OUT_RATE        48000
-#define CONV_FRAMES     4096            // per rate converter call
 
-static esp_ae_rate_cvt_handle_t s_cvt;  // NULL: no conversion (source is 48 kHz)
+static audio_conv_t *s_conv;            // HLS: s16 -> 48 kHz -> ring
-static uint32_t s_cvt_rate;             // input rate the converter was opened for
-static int32_t *s_in32, *s_out32;       // stereo int32 work buffers (PSRAM)
 static uint64_t s_seg_out;              // 48 kHz frames written this segment
 
 static esp_audio_simple_dec_handle_t s_dec;
@@ -45,51 +41,6 @@ static void report_segment(void)
     s_seg_count++;
 }
 
-// Decoded PCM (s16, any channel count) -> stereo int32 -> 48 kHz -> ring.
-static void output_pcm(const int16_t *pcm, uint32_t frames)
-{
-    int ch = s_info.channel;
-    if (s_info.sample_rate != s_cvt_rate) {
-        if (s_cvt) {
-            esp_ae_rate_cvt_close(s_cvt);
-            s_cvt = NULL;
-        }
-        s_cvt_rate = s_info.sample_rate;
-        if (s_cvt_rate != OUT_RATE) {
-            esp_ae_rate_cvt_cfg_t cfg = {
-                .src_rate = s_cvt_rate, .dest_rate = OUT_RATE, .channel = 2, .bits_per_sample = 32,
-                .complexity = 3, .perf_type = ESP_AE_RATE_CVT_PERF_TYPE_SPEED,
-            };
-            if (esp_ae_rate_cvt_open(&cfg, &s_cvt) != ESP_AE_ERR_OK) {
-                ESP_LOGE(TAG, "rate converter %lu -> %d Hz: open failed", (unsigned long)s_cvt_rate, OUT_RATE);
-            } else {
-                ESP_LOGI(TAG, "rate converter %lu -> %d Hz", (unsigned long)s_cvt_rate, OUT_RATE);
-            }
-        }
-    }
-    while (frames) {
-        uint32_t n = frames < CONV_FRAMES ? frames : CONV_FRAMES;
-        for (uint32_t i = 0; i < n; i++) {      // to stereo int32 (full scale = INT32_MAX)
-            int32_t l = (int32_t)pcm[i * ch] << 16;
-            s_in32[i * 2] = l;
-            s_in32[i * 2 + 1] = ch > 1 ? (int32_t)pcm[i * ch + 1] << 16 : l;
-        }
-        const int32_t *out = s_in32;
-        uint32_t out_n = n;
-        if (s_cvt) {
-            out_n = CONV_FRAMES * 2;
-            if (esp_ae_rate_cvt_process(s_cvt, s_in32, n, s_out32, &out_n) != ESP_AE_ERR_OK) {
-                ESP_LOGW(TAG, "rate conversion failed");
-                return;
-            }
-            out = s_out32;
-        }
-        s_seg_out += player_write(out, out_n);
-        pcm += n * ch;
-        frames -= n;
-    }
-}
-
 // Feed ADTS-AAC elementary stream bytes to the decoder.
 static void decode_es(const uint8_t *data, size_t len)
 {
@@ -121,7 +72,8 @@ static void decode_es(const uint8_t *data, size_t len)
             uint32_t n = out.decoded_size / (s_info.channel * s_info.bits_per_sample / 8);
             s_seg_frames += n;
             if (s_info.bits_per_sample == 16) {
-                output_pcm((const int16_t *)out.buffer, n);
+                s_seg_out += audio_conv_write(s_conv, (const int16_t *)out.buffer, n, s_info.channel,
+                                              s_info.sample_rate);
             }
         }
         raw.buffer += raw.consumed;
@@ -228,7 +180,6 @@ esp_err_t decoder_init(void)
         return ESP_FAIL;
     }
     s_pcm = heap_caps_malloc(s_pcm_size, MALLOC_CAP_SPIRAM);
-    s_in32 = heap_caps_malloc(CONV_FRAMES * 2 * sizeof(int32_t), MALLOC_CAP_SPIRAM);
+    s_conv = audio_conv_create(PLAYER_SRC_HLS, "hls");
-    s_out32 = heap_caps_malloc(CONV_FRAMES * 2 * 2 * sizeof(int32_t), MALLOC_CAP_SPIRAM);
+    return s_pcm && s_conv ? ESP_OK : ESP_ERR_NO_MEM;
-    return s_pcm && s_in32 && s_out32 ? ESP_OK : ESP_ERR_NO_MEM;
 }

main/player.c

@@ -5,9 +5,11 @@
 #include "aes67_cfg.h"
 #include "aes67_tx.h"
 #include "aes67_web.h"
+#include "audio_out.h"
 #include "audio_ring.h"
 #include "decoder.h"
 #include "hls.h"
+#include "spotify.h"
 #include "esp_log.h"
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"
@@ -19,17 +21,18 @@
 
 static const char *TAG = "player";
 
-typedef enum { SRC_TONE, SRC_OFF, SRC_HLS, SRC_SPOTIFY } src_t;
 static const char *const SRC_NAME[] = { "tone", "off", "hls", "spotify" };
 
-static volatile src_t s_src = SRC_OFF;
+static volatile player_src_t s_src = PLAYER_SRC_OFF;
 static volatile bool s_playing;         // ring output running (after prefill)
 static volatile bool s_flush;           // consumer drops buffered audio on the next read
+static volatile bool s_paused;          // Spotify paused: silence, buffer kept, no underrun
+static audio_conv_t *s_spotify_conv;
 
-static src_t mode_of(const char *m)
+static player_src_t mode_of(const char *m)
 {
-    return !strcmp(m, "tone") ? SRC_TONE : !strcmp(m, "hls") ? SRC_HLS :
+    return !strcmp(m, "tone") ? PLAYER_SRC_TONE : !strcmp(m, "hls") ? PLAYER_SRC_HLS :
-           !strcmp(m, "spotify") ? SRC_SPOTIFY : !strcmp(m, "auto") ? SRC_HLS /* failover: step 7 */ : SRC_OFF;
+           !strcmp(m, "spotify") ? PLAYER_SRC_SPOTIFY : !strcmp(m, "auto") ? PLAYER_SRC_HLS /* failover: step 7 */ : PLAYER_SRC_OFF;
 }
 
 // AES67 TX pull callback (TX task, must not block). Silence while buffering or off: not an underrun.
@@ -40,7 +43,7 @@ static size_t player_read(int32_t *buf, size_t frames)
         s_flush = false;
         s_playing = false;
     }
-    if (s_src == SRC_OFF || s_src == SRC_SPOTIFY) {     // Spotify: step 7 (cspot)
+    if (s_src == PLAYER_SRC_OFF || (s_src == PLAYER_SRC_SPOTIFY && s_paused)) {
         memset(buf, 0, frames * CHANNELS * sizeof(int32_t));
         return frames;
     }
@@ -60,25 +63,25 @@ static size_t player_read(int32_t *buf, size_t frames)
 
 void player_apply(const cJSON *source)
 {
-    src_t src = mode_of(cJSON_GetObjectItemCaseSensitive(source, "mode")->valuestring);
+    player_src_t src = mode_of(cJSON_GetObjectItemCaseSensitive(source, "mode")->valuestring);
     if (src == s_src) {
         return;
     }
     s_src = src;
     s_flush = true;
     // The test tone is TX's own (phase-locked to PTP); everything else goes through player_read.
-    aes67_tx_set_source(src == SRC_TONE ? NULL : player_read);
+    aes67_tx_set_source(src == PLAYER_SRC_TONE ? NULL : player_read);
     ESP_LOGI(TAG, "source: %s", SRC_NAME[src]);
 }
 
-// Source side (HLS task): write converted 48 kHz frames, waiting for space at playback speed.
+// Source side: write converted 48 kHz frames, waiting for space at playback speed.
-// Gives up when the source is no longer HLS.
+// Frames of a source that is not active are dropped.
-size_t player_write(const int32_t *frames, size_t n)
+size_t player_write(player_src_t src, const int32_t *frames, size_t n)
 {
     size_t done = 0;
     while (done < n) {
-        if (s_src != SRC_HLS) {
+        if (s_src != src) {
-            return done;
+            return n;               // not the active source: drop
         }
         size_t w = audio_ring_write(frames + done * CHANNELS, n - done);
         if (!w) {
@@ -89,13 +92,41 @@ size_t player_write(const int32_t *frames, size_t n)
     return done;
 }
 
+/* ----- Spotify ----- */
+
+static size_t spotify_pcm(const int16_t *pcm, size_t frames)
+{
+    audio_conv_write(s_spotify_conv, pcm, frames, 2, 44100);   // blocks while the ring is full
+    return frames;
+}
+
+static void spotify_event(spotify_event_t ev, int value)
+{
+    switch (ev) {
+    case SPOTIFY_EV_PLAY:
+        s_paused = false;
+        break;
+    case SPOTIFY_EV_PAUSE:
+        s_paused = true;
+        break;
+    case SPOTIFY_EV_FLUSH:
+        if (s_src == PLAYER_SRC_SPOTIFY) {
+            s_flush = true;         // skip/seek: don't play out the old buffer
+        }
+        break;
+    case SPOTIFY_EV_VOLUME:
+        ESP_LOGI(TAG, "Spotify volume %d%% (applied in step 7.5b4)", value * 100 / 65535);
+        break;
+    }
+}
+
 static void player_status(cJSON *st)
 {
-    const char *state = s_src == SRC_TONE ? "playing" : s_src == SRC_OFF ? "idle" :
+    const char *state = s_src == PLAYER_SRC_TONE ? "playing" : s_src == PLAYER_SRC_OFF ? "idle" :
-                        s_src == SRC_SPOTIFY ? "not implemented" : s_playing ? "playing" : "buffering";
+                        s_src == PLAYER_SRC_SPOTIFY && s_paused ? "paused" : s_playing ? "playing" : "buffering";
     cJSON_AddStringToObject(st, "active_source", SRC_NAME[s_src]);
     cJSON_AddStringToObject(st, "source_state", state);
-    cJSON_AddStringToObject(st, "spotify_state", "not implemented");
+    cJSON_AddStringToObject(st, "spotify_state", spotify_state());
     cJSON_AddNumberToObject(st, "buffer_ms", (double)(audio_ring_level() * 1000 / RATE));
 }
 
@@ -107,13 +138,18 @@ esp_err_t player_init(void)
         return err;
     }
     cJSON *src = cfg_get("source");
-    s_src = (src_t)-1;
+    s_src = (player_src_t)-1;
     player_apply(src);
     cJSON_Delete(src);
     err = decoder_init();
     if (err != ESP_OK) {
         return err;
     }
+    s_spotify_conv = audio_conv_create(PLAYER_SRC_SPOTIFY, "spotify");
+    if (!s_spotify_conv) {
+        return ESP_ERR_NO_MEM;
+    }
+    spotify_init(spotify_pcm, spotify_event);
         err = hls_start(decoder_feed);
     if (err != ESP_OK) {
         return err;

main/player.h

@@ -7,8 +7,11 @@
 #include "cJSON.h"
 #include "esp_err.h"
 
+typedef enum { PLAYER_SRC_TONE, PLAYER_SRC_OFF, PLAYER_SRC_HLS, PLAYER_SRC_SPOTIFY } player_src_t;
+
 esp_err_t player_init(void);
 // Apply the "source" config group (mode etc.).
 void player_apply(const cJSON *source);
 // Source side: write 48 kHz stereo int32 frames, blocking while the ring is full.
-size_t player_write(const int32_t *frames, size_t n);
+// Frames from a source that is not the active one are dropped (returns n).
+size_t player_write(player_src_t src, const int32_t *frames, size_t n);

main/project_cfg.c

@@ -7,7 +7,8 @@
 
 static const char SOURCE_DEFAULTS[] =
     "{\"mode\":\"spotify\",\"spotify_name\":\"P4 AES67\",\"spotify_bitrate\":320,\"hls_url\":\"\","
-    "\"autoplay\":false,\"gain_db\":0,\"failover_delay_s\":5,\"failover_on_pause\":false}";
+    "\"autoplay\":false,\"gain_db\":0,\"failover_delay_s\":5,\"failover_on_pause\":false,"
+    "\"spotify_client_id\":\"\",\"spotify_client_secret\":\"\"}";
 
 static bool source_validate(const cJSON *g, char *err, size_t n)
 {
@@ -17,6 +18,8 @@ static bool source_validate(const cJSON *g, char *err, size_t n)
            cfg_check_str(g, "spotify_name", 1, 63, err, n) &&
            cfg_check_num_in(g, "spotify_bitrate", bitrates, 3, err, n) &&
            cfg_check_str(g, "hls_url", 0, 255, err, n) &&
+           cfg_check_str(g, "spotify_client_id", 0, 64, err, n) &&
+           cfg_check_str(g, "spotify_client_secret", 0, 64, err, n) &&
            cfg_check_num(g, "gain_db", -60, 12, err, n) &&
            cfg_check_int(g, "failover_delay_s", 0, 3600, err, n);
 }
@@ -31,4 +34,6 @@ void project_cfg_defaults(void)
 void project_cfg_register(void)
 {
     ESP_ERROR_CHECK(cfg_register("source", SOURCE_DEFAULTS, source_validate, player_apply));
+    // Each user's own Spotify developer app (developer.spotify.com); the secret is write-only.
+    ESP_ERROR_CHECK(cfg_mark_secret("source", "spotify_client_secret"));
 }

sdkconfig.defaults

@@ -28,3 +28,11 @@ CONFIG_LWIP_MAX_SOCKETS=16
 # 32 MB PSRAM in the P4 package (hex mode, 200 MHz; 250 MHz needs rev >= 3). Needed for step 7:
 # HLS segment buffers, cspot, decoders. malloc() puts blocks >16 KB in PSRAM; DMA buffers stay internal.
 CONFIG_SPIRAM=y
+
+# cspot (Spotify Connect, step 7.5) needs C++ exceptions.
+CONFIG_COMPILER_CXX_EXCEPTIONS=y
+
+# esp_audio_codec's Vorbis decoder exports the same symbols (vorbis_info_init, ...) as cspot's
+# Tremor (bell): keep it out of the link. HLS only needs AAC.
+# CONFIG_AUDIO_DECODER_VORBIS_SUPPORT is not set
+# CONFIG_AUDIO_SIMPLE_DEC_OGG_SUPPORT is not set

web/index.html

@@ -71,6 +71,11 @@ e.g. curl -X POST http://p4-aes67.local/api/player/next
 <label><span>Spotify device name</span><input name="source.spotify_name"></label>
 <label><span>Spotify bitrate</span><select name="source.spotify_bitrate">
   <option>96</option><option>160</option><option>320</option></select></label>
+<label><span>Spotify client ID</span><input name="source.spotify_client_id" autocomplete="off"></label>
+<label><span>Spotify client secret</span><input name="source.spotify_client_secret" type="password"
+  autocomplete="new-password" placeholder="stored; leave empty to keep"></label>
+<small>Your own app from <a href="https://developer.spotify.com/dashboard" target="_blank">developer.spotify.com</a>
+  (Premium account). The secret is never shown again once saved.</small>
 <label><span>Stream URL</span><input name="source.hls_url" type="url" placeholder="https://…/playlist.m3u8"></label>
 <label><span>Autoplay stream on boot</span><input name="source.autoplay" type="checkbox"></label>
 <label><span>Output gain (dB)</span><input name="source.gain_db" type="number" min="-60" max="12" step="0.5"></label>
@@ -208,7 +213,7 @@ const PROJECT = {
   title: 'P4 AES67 Streamer',
   def: {
     source:{mode:'spotify',spotify_name:'P4 AES67',spotify_bitrate:'320',hls_url:'',autoplay:false,gain_db:0,
-            failover_delay_s:5,failover_on_pause:false},
+            failover_delay_s:5,failover_on_pause:false,spotify_client_id:'',spotify_client_secret:''},
     aes67:{name:'P4 AES67'},
     net:{hostname:'p4-aes67'}
   },
@@ -216,6 +221,7 @@ const PROJECT = {
     const m = f['source.mode'].value;
     const sp = m === 'spotify' || m === 'auto', hl = m === 'hls' || m === 'auto';
     f['source.spotify_name'].disabled = f['source.spotify_bitrate'].disabled = !sp;
+    f['source.spotify_client_id'].disabled = f['source.spotify_client_secret'].disabled = !sp;
     f['source.hls_url'].disabled = !hl;
     f['source.autoplay'].disabled = m !== 'hls';
     f['source.failover_delay_s'].disabled = f['source.failover_on_pause'].disabled = m !== 'auto';