Log what the master offers and let the caller pin audio or video

The recorder passed no -f, so yt-dlp used its default, which prefers video.
That was never a decision: on 2 Sep the master held exactly one rendition, so
there was nothing to choose between. If a master ever carries a video variant
the account is not entitled to, the default would take it and 403 on segments.

--prefer audio|video|best makes it explicit. best keeps the old behaviour.

Every run now logs the renditions the master advertises, parsed from
EXT-X-STREAM-INF, so we build evidence about whether video and audio ever
appear together instead of assuming entitlement shapes the master.

Observed so far, both audio nights: one rendition, mp4a.40.2 at 140 kbps.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Kyt7QHQvLJtQRuiY4wAqKB

record_live.py

@@ -106,7 +106,35 @@ def mint_master(entry_id):
                  "Referer": "https://www.bristolrovers.co.uk/"})
     data = json.loads(urllib.request.urlopen(req, timeout=20)
                       .read().decode("utf-8", "replace"))
-    return (data.get("media") or {}).get("hls") or None
+    hls = (data.get("media") or {}).get("hls") or None
+    if hls:
+        log_renditions(hls)
+    return hls
+
+
+def log_renditions(master_url):
+    """Record what the master offers. We have never seen one carrying both
+    video and audio, so log it every time until we know how that looks."""
+    import urllib.request
+    try:
+        req = urllib.request.Request(master_url, headers={"User-Agent": UA,
+              "Referer": "https://www.bristolrovers.co.uk/"})
+        body = urllib.request.urlopen(req, timeout=15).read().decode("utf-8", "replace")
+    except Exception as exc:
+        log(f"  (could not read master for rendition list: {exc})")
+        return
+    PREFIX = "#EXT-X-STREAM-INF:"
+    streams = [ln[len(PREFIX):] for ln in body.splitlines()
+               if ln.startswith(PREFIX)]
+    log(f"  master offers {len(streams)} rendition(s):")
+    for st in streams:
+        bw = re.search(r"BANDWIDTH=(\d+)", st)
+        res = re.search(r"RESOLUTION=([\dx]+)", st)
+        cod = re.search(r'CODECS="([^"]+)"', st)
+        codecs = cod.group(1) if cod else "?"
+        kind = "audio-only" if ("avc" not in codecs and "hvc" not in codecs) else "video"
+        log(f"    {kind:11s} {int(bw.group(1))//1000 if bw else '?':>6} kbps  "
+            f"{res.group(1) if res else '-':>10}  {codecs}")
 
 
 def find_manifest(timeout_s=90):
@@ -175,7 +203,7 @@ def find_manifest(timeout_s=90):
     return m.group(1) if m else None
 
 
-def record(url, duration_min):
+def record(url, duration_min, prefer='best'):
     stamp = datetime.now().strftime("%Y%m%d-%H%M%S")
     out = os.path.join(RECORDINGS, f"brfc-{stamp}.ts")
     os.makedirs(RECORDINGS, exist_ok=True)
@@ -197,8 +225,14 @@ def record(url, duration_min):
         "-reconnect_delay_max 30",
         "--downloader-args", f"ffmpeg_o:-t {duration_min * 60}",
         "-o", out,
-        url,
     ]
+    if prefer == "audio":
+        # Pin audio when the entitlement is audio-only: if a video rendition
+        # ever appears in the master, taking it would 403 on the segments.
+        cmd += ["-f", "bestaudio/best"]
+    elif prefer == "video":
+        cmd += ["-f", "bestvideo*+bestaudio/best"]
+    cmd.append(url)
     log(f"recording -> {os.path.basename(out)}  (cap {duration_min} min)")
     log(f"  yt-dlp log -> {os.path.basename(logfile)}")
     with open(logfile, "w", encoding="utf-8") as fh:
@@ -213,6 +247,9 @@ def main():
     ap.add_argument("--duration", type=int, default=150,
                     help="recording cap in minutes")
     ap.add_argument("--poll", type=int, default=60, help="seconds between attempts")
+    ap.add_argument("--prefer", choices=("best", "audio", "video"), default="best",
+                    help="which rendition to take when the master offers both; "
+                         "'best' is yt-dlp's default and prefers video")
     args = ap.parse_args()
 
     if args.at:
@@ -244,7 +281,7 @@ def main():
                 time.sleep(args.poll)
                 continue
             log("  minted fresh master playlist")
-            proc = record(url, args.duration)
+            proc = record(url, args.duration, args.prefer)
             log(f"  downloader pid {proc.pid}; waiting for it to finish")
             t0 = time.time()
             proc.wait()