Audio capture and streaming app for webOS 5/6

Captures the TV's audio and sends it out over several transports. The
primary one is HyperHDR: RTP/L16 to a host-side loopback device, since
HyperHDR has no network audio input of its own. A second route renders
the spectrum on the TV and sends FlatBuffers images to port 19400
instead, for setups where touching the host's sound config is not an
option.

  native/       the service: capture backends (PulseAudio, ALSA, exec,
                test tone, all dlopen-based), DSP, and one file per sink
  frontend/     D-pad driven UI at a fixed 1920x1080
  servicefiles/ native service manifest plus the boot script
  host/         RTP receiver and the loopback installer for the HyperHDR
                machine
  tools/        build/package, asset generation, Homebrew Channel
                manifest, on-TV probe
  test/         host-side suites: FlatBuffers and RTP verified against
                real decoders, the engine end to end, the page in jsdom

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

native/src/main.c

@@ -0,0 +1,123 @@
+// Entry point for the native Luna service.
+//
+// Nothing interesting happens here: register on the bus, hand control to the
+// glib main loop, and make sure a SIGTERM from the service launcher shuts the
+// capture down cleanly so sinks get to say goodbye (HyperHDR in particular
+// needs its Clear, or the LEDs freeze on the last frame we sent).
+
+#include "common/log.h"
+#include "service.h"
+
+#include <glib-unix.h>
+#include <glib.h>
+#include <luna-service2/lunaservice.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define SERVICE_NAME "org.webosbrew.audiocap.service"
+
+// webOS 3.5 and earlier need the service registered on the public bus too.
+// Declared weak so the same binary keeps loading on newer firmware where the
+// symbol was removed.
+extern bool LSRegisterPubPriv(const char* name, LSHandle** handle, bool public_bus,
+    LSError* error) __attribute__((weak));
+
+static gboolean on_signal(gpointer user)
+{
+    GMainLoop* loop = user;
+    INFO("Signal received, shutting down");
+    g_main_loop_quit(loop);
+    return G_SOURCE_REMOVE;
+}
+
+static void log_environment(void)
+{
+    uid_t uid = getuid();
+    INFO("lgtv-audio-cap service starting (uid=%d%s)", (int)uid,
+        uid == 0 ? ", root" : ", unprivileged");
+    if (uid != 0) {
+        // Without root the PulseAudio socket and the ALSA devices are usually
+        // out of reach, so say this once rather than leaving the user to
+        // decode a permission error later.
+        WARN("Not running as root: audio devices are likely inaccessible.");
+        WARN("Install the Homebrew Channel 'elevate-service' patch and restart the service.");
+    }
+}
+
+int main(int argc, char** argv)
+{
+    bool debug = false;
+    for (int i = 1; i < argc; i++) {
+        if (strcmp(argv[i], "-d") == 0 || strcmp(argv[i], "--debug") == 0)
+            debug = true;
+    }
+
+    log_init(debug ? LOG_DEBUG : LOG_INFO);
+    log_environment();
+
+    // A client that hangs up mid-stream must not kill the service. Every send
+    // path already asks for MSG_NOSIGNAL; this covers the rest.
+    signal(SIGPIPE, SIG_IGN);
+
+    GMainLoop* loop = g_main_loop_new(NULL, false);
+
+    LSError lserror;
+    LSErrorInit(&lserror);
+
+    LSHandle* handle = NULL;
+    bool registered = LSRegisterPubPriv
+        ? LSRegisterPubPriv(SERVICE_NAME, &handle, true, &lserror)
+        : LSRegister(SERVICE_NAME, &handle, &lserror);
+    if (!registered) {
+        ERR("Cannot register %s on the Luna bus: %s", SERVICE_NAME, lserror.message);
+        LSErrorFree(&lserror);
+        g_main_loop_unref(loop);
+        return 1;
+    }
+
+    if (!LSGmainAttach(handle, loop, &lserror)) {
+        ERR("Cannot attach to the main loop: %s", lserror.message);
+        LSErrorFree(&lserror);
+        LSUnregister(handle, &lserror);
+        g_main_loop_unref(loop);
+        return 1;
+    }
+
+    service_t* service = service_create(handle, loop);
+    if (!service) {
+        ERR("Cannot create the service");
+        LSUnregister(handle, &lserror);
+        g_main_loop_unref(loop);
+        return 1;
+    }
+
+    char err[256] = { 0 };
+    if (!service_register(service, err, sizeof(err))) {
+        ERR("%s", err);
+        service_destroy(service);
+        LSUnregister(handle, &lserror);
+        g_main_loop_unref(loop);
+        return 1;
+    }
+
+    g_unix_signal_add(SIGTERM, on_signal, loop);
+    g_unix_signal_add(SIGINT, on_signal, loop);
+
+    INFO("Registered as %s", SERVICE_NAME);
+    service_autostart(service);
+
+    g_main_loop_run(loop);
+
+    INFO("Shutting down");
+    service_destroy(service);
+
+    if (!LSUnregister(handle, &lserror)) {
+        ERR("Unregister failed: %s", lserror.message);
+        LSErrorFree(&lserror);
+    }
+    g_main_loop_unref(loop);
+    return 0;
+}