audio: avoid returning audio-device-list entries without description

Use the device name as fallback. This is ugly, but still better than
skipping the description entirely. This can be an issue on ALSA, where
the API can return entries without proper description.

DOCS/interface-changes.rst

@@ -95,6 +95,8 @@ Interface changes
       --terminal, --osc, --ytdl, can all be enable/disabled after
       mpv_initialize() - this can be extended to other still fixed options
       on user requests)
+    - the "audio-device-list" property now sets empty device description to the
+      device name as a fallback
  --- mpv 0.20.0 ---
     - add --image-display-duration option - this also means that image duration
       is not influenced by --mf-fps anymore in the general case (this is an

DOCS/man/input.rst

@@ -1912,8 +1912,9 @@ Property list
 
     The ``name`` is what is to be passed to the ``--audio-device`` option (and
     often a rather cryptic audio API-specific ID), while ``description`` is
-    human readable free form text. The description is an empty string if none
-    was received.
+    human readable free form text. The description is set to the device name
+    (minus mpv-specific ``<driver>/`` prefix) if no description is available
+    or the description would have been an empty string.
 
     The special entry with the name set to ``auto`` selects the default audio
     output driver and the default device.

audio/out/ao.c

@@ -599,6 +599,8 @@ void ao_device_list_add(struct ao_device_list *list, struct ao *ao,
 {
     struct ao_device_desc c = *e;
     const char *dname = ao->driver->name;
+    if ((!c.desc || !c.desc[0]) && c.name)
+        c.desc = c.name;
     c.name = c.name[0] ? talloc_asprintf(list, "%s/%s", dname, c.name)
                        : talloc_strdup(list, dname);
     c.desc = talloc_strdup(list, c.desc);