fix(fmrelay): start path + JSON API + mounts XML + inline live preview

Four bugs surfaced when actually running a relay live (#377):

1. cmd_start sanity check still referenced lame_present after the
   ffmpeg switch — every start failed with
   `fmrelayctl: line 209: lame_present: command not found`.
   Renamed to ffmpeg_present.

2. log()/warn() wrote the human banner to stdout, which the API's
   subprocess.check_output(..., stderr=subprocess.STDOUT) merged into
   the JSON parser. /start returned 500 even when the runner spawned
   correctly. log() now writes to stderr; api/_ctl_json switches to
   subprocess.run(capture_output=True) so stdout stays clean JSON
   and stderr is only surfaced on failure.

3. emit_mounts_json grep'd `<mount>...</mount>` elements but icecast2
   /admin/listmounts uses `<source mount="...">` attribute form. The
   mounts table always showed empty. New parser handles the real XML
   shape + reports connected_sec + content_type alongside listeners.

4. admin webui had only the "Open Webradio →" link (which targets a
   vhost that doesn't exist yet). Added a card with `<audio controls>`
   that auto-binds to the active LAN mount via /access + /mounts,
   so the operator can verify playback without leaving the dashboard.

packages/secubox-fmrelay/api/main.py

@@ -45,18 +45,22 @@ app = FastAPI(
 
 
 def _ctl_json(*args: str) -> Dict[str, Any]:
-    """Invoke fmrelayctl with --json and parse the result."""
+    """Invoke fmrelayctl with --json and parse the result.
+
+    stderr is captured separately so human-readable log lines from
+    `log()` don't pollute the JSON parser on stdout. The captured
+    stderr is only surfaced when the call fails."""
     cmd = [CTL, *args, "--json"]
     try:
-        out = subprocess.check_output(cmd, stderr=subprocess.STDOUT, timeout=15)
+        proc = subprocess.run(cmd, capture_output=True, timeout=15, check=True)
     except subprocess.CalledProcessError as e:
-        raise HTTPException(status_code=500, detail=f"fmrelayctl failed: {e.output!r}")
+        raise HTTPException(status_code=500, detail=f"fmrelayctl failed: {e.stderr!r}")
     except FileNotFoundError:
         raise HTTPException(status_code=500, detail=f"fmrelayctl not found at {CTL}")
     try:
-        return json.loads(out.decode())
+        return json.loads(proc.stdout.decode())
     except json.JSONDecodeError as e:
-        raise HTTPException(status_code=500, detail=f"fmrelayctl non-JSON: {e}; raw={out!r}")
+        raise HTTPException(status_code=500, detail=f"fmrelayctl non-JSON: {e}; stdout={proc.stdout!r}; stderr={proc.stderr!r}")
 
 
 def _ctl_text(*args: str) -> str:

packages/secubox-fmrelay/sbin/fmrelayctl

@@ -31,7 +31,7 @@ readonly GREEN='\033[0;32m'
 readonly YELLOW='\033[1;33m'
 readonly NC='\033[0m'
 
-log()  { printf '%b[fmrelay]%b %s\n' "$GREEN" "$NC" "$*"; }
+log()  { printf '%b[fmrelay]%b %s\n' "$GREEN" "$NC" "$*" >&2; }
 warn() { printf '%b[warn]%b %s\n' "$YELLOW" "$NC" "$*" >&2; }
 err()  { printf '%b[error]%b %s\n' "$RED" "$NC" "$*" >&2; }
 
@@ -165,13 +165,28 @@ emit_mounts_json() {
         return
     fi
     # Hand-parse the XML response — full XML parser would need lxml as
-    # a hard dep on the host. icecast's <listmounts> shape is stable.
+    # a hard dep on the host. icecast2 /admin/listmounts shape:
+    #   <source mount="/foo.mp3">
+    #     <listeners>0</listeners>
+    #     <Connected>63</Connected>
+    #     <content-type>audio/mpeg</content-type>
+    #   </source>
     python3 - <<PY
 import re, json
 xml = """${raw//\"/\\\"}"""
 mounts = []
-for m in re.finditer(r"<mount>([^<]+)</mount>.*?<listeners>(\d+)</listeners>", xml, re.S):
-    mounts.append({"mount": m.group(1), "listeners": int(m.group(2))})
+for m in re.finditer(r'<source\b[^>]*\bmount="([^"]+)"[^>]*>(.*?)</source>', xml, re.S):
+    mount, body = m.group(1), m.group(2)
+    def field(name):
+        mm = re.search(rf"<{name}>([^<]*)</{name}>", body)
+        return mm.group(1) if mm else ""
+    listeners = field("listeners") or "0"
+    mounts.append({
+        "mount": mount,
+        "listeners": int(listeners),
+        "connected_sec": int(field("Connected") or 0),
+        "content_type": field("content-type"),
+    })
 print(json.dumps({"module": "fmrelay", "mounts": mounts}))
 PY
 }
@@ -206,7 +221,7 @@ cmd_start() {
 
     if ! icecast_running;  then err "icecast2 not running on ${ICECAST_HOST}:${ICECAST_PORT}"; exit 2; fi
     if ! rtl_fm_present;   then err "rtl_fm not installed (apt install rtl-sdr)"; exit 2; fi
-    if ! lame_present;     then err "lame not installed (apt install lame)"; exit 2; fi
+    if ! ffmpeg_present;   then err "ffmpeg not installed (apt install ffmpeg)"; exit 2; fi
 
     log "Starting fmrelay: freq=$freq mount=$mount bitrate=${bitrate}k gain=${gain}dB ppm=${ppm}"
     echo "$freq"  > "$CURRENT_FREQ_FILE"

packages/secubox-fmrelay/www/fmrelay/index.html

@@ -67,6 +67,18 @@
     </a>
   </header>
 
+  <section class="card" style="margin-bottom: 1rem;">
+    <h3>Live preview</h3>
+    <p class="hint" style="margin-bottom: 0.5rem;">
+      Direct playback of the active LAN mount — handy to verify the stream
+      is healthy without leaving the dashboard.
+    </p>
+    <audio id="live-audio" controls preload="none" style="width: 100%; max-width: 500px;"></audio>
+    <div id="live-audio-meta" style="margin-top: 0.5rem; font-size: 0.85rem; color: var(--muted);">
+      no active mount
+    </div>
+  </section>
+
   <section class="cards">
     <article class="card">
       <h3>Status</h3>
@@ -180,6 +192,11 @@
       const target = (pub && pub.url) || (lan && lan.url) || "#";
       const btn = document.getElementById("open-webradio");
       if (btn) btn.href = target;
+
+      // Cache the LAN base for refreshLivePreview() (called by loadMounts
+      // once the mounts list is in — avoids relying on poll order).
+      window._fmrelayLanBase = (lan && lan.url) ? lan.url.replace(/\/$/, "") : "";
+      refreshLivePreview();
     } catch (e) {
       document.getElementById("access-v").innerHTML = `<span class="empty">${esc(e.message)}</span>`;
     }
@@ -209,6 +226,8 @@
     try {
       const d = await api("/mounts");
       const list = d.mounts || [];
+      window._fmrelayLastMounts = list;
+      refreshLivePreview();
       if (!list.length) {
         wrap.innerHTML = `<div class="empty">no active mounts${d.reason ? " — " + esc(d.reason) : ""}</div>`;
         return;
@@ -257,6 +276,24 @@
     }
   }
 
+  function refreshLivePreview() {
+    try {
+      const audio = document.getElementById("live-audio");
+      const meta  = document.getElementById("live-audio-meta");
+      const base  = window._fmrelayLanBase || "";
+      const mounts = window._fmrelayLastMounts || [];
+      const liveMount = mounts.find(m => (m.connected_sec || 0) > 0);
+      if (audio && base && liveMount) {
+        const url = base + liveMount.mount;
+        if (audio.getAttribute("src") !== url) audio.setAttribute("src", url);
+        if (meta) meta.textContent = `mount ${liveMount.mount} · ${liveMount.connected_sec}s · ${liveMount.content_type || ""}`;
+      } else if (audio) {
+        audio.removeAttribute("src");
+        if (meta) meta.textContent = "no active mount — start a relay below";
+      }
+    } catch (_) {}
+  }
+
   function loadAll() {
     loadStatus();
     loadComponents();