From b31f29024a55d06c1bf26273e41fddb2c3b87457 Mon Sep 17 00:00:00 2001
From: ed <s@ocv.me>
Date: Mon, 20 Apr 2026 20:39:14 +0200
Subject: [PATCH] audioplayer: opus: enforce 1ch or 2ch; downmix 3+

---
 copyparty/mtag.py   | 1 +
 copyparty/th_srv.py | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/copyparty/mtag.py b/copyparty/mtag.py
index 1d4df60e..38caeb21 100644
--- a/copyparty/mtag.py
+++ b/copyparty/mtag.py
@@ -216,6 +216,7 @@ def au_unpk(
 def ffprobe(
     abspath: str, timeout: int = 60
 ) -> tuple[dict[str, tuple[int, Any]], dict[str, list[Any]], list[Any], dict[str, Any]]:
+    # ffprobe -hide_banner -show_streams -show_format --
     cmd = [
         b"ffprobe",
         b"-hide_banner",
diff --git a/copyparty/th_srv.py b/copyparty/th_srv.py
index 93ce8c22..eb039e3f 100644
--- a/copyparty/th_srv.py
+++ b/copyparty/th_srv.py
@@ -1219,6 +1219,13 @@ class ThumbSrv(object):
         self.log("conv2 %s [%s]" % (container, enc), 6)
         benc = enc.encode("ascii").split(b" ")
 
+        ac = b"2"
+        try:
+            if tags["chs"][1] in ("mono", "1", "1.0"):
+                ac = b"1"
+        except:
+            pass
+
         # fmt: off
         cmd = [
             b"ffmpeg",
@@ -1228,6 +1235,7 @@ class ThumbSrv(object):
             b"-i", fsenc(abspath),
         ] + tagset + [
             b"-map", b"0:a:0",
+            b"-ac", ac,
         ] + benc + [
             b"-f", container,
             fsenc(tpath)
@@ -1268,6 +1276,7 @@ class ThumbSrv(object):
             b"-i", fsenc(abspath),
             b"-map_metadata", b"-1",
             b"-map", b"0:a:0",
+            b"-ac", b"2",
         ] + benc + [
             b"-f", b"opus",
             fsenc(tmp_opus)