fix(music): drive mpv as a direct subprocess for reliable playback

EMMS drove mpv over an IPC socket, starting it idle and sending loadfile across the socket. That handshake left mpv loaded but never streaming, so playback silently failed and the playing flag never set. I replaced it with a subprocess player that runs mpv with the track as a direct argument, the invocation that plays every time. Pause works in place through process signals, SIGSTOP and SIGCONT. In-track seek is gone, the deliberate trade for reliability. --no-config isolates this mpv from the interactive video setup so the two cannot interfere, and it follows the system default audio sink.

1 files changed, 59 insertions, 16 deletions

diff --git a/modules/music-config.el b/modules/music-config.el
index 76fff283b..fb8febc36 100644
--- a/modules/music-config.el
+++ b/modules/music-config.el
@@ -108,8 +108,6 @@
 (defvar emms-random-playlist)
 (defvar emms-playlist-selected-marker)
 (defvar emms-source-file-default-directory)
-(defvar emms-player-mpv-parameters)
-(defvar emms-player-mpv-regexp)
 (defvar emms-player-playing-p)
 (defvar emms-player-paused-p)
 (defvar emms-playlist-mode-map)
@@ -149,6 +147,57 @@
 (defvar cj/music-playlist-buffer-name "*EMMS-Playlist*"
   "Name of the EMMS playlist buffer used by this configuration.")
 
+;;; Subprocess mpv player (reliable playback)
+
+;; The IPC player (emms-player-mpv) drives mpv over a socket -- start mpv idle,
+;; connect, send loadfile.  That handshake was leaving mpv loaded but never
+;; streaming, so playback silently failed.  Driving mpv with the track as a
+;; direct argument -- the invocation that plays every time -- is the reliable
+;; path.  --no-config isolates this mpv from the interactive/video mpv setup so
+;; the two cannot interfere.  Pause is in place via process signals; in-track
+;; seek is not available with a subprocess player (the trade for reliability).
+
+(declare-function emms-player "emms")
+(declare-function emms-player-set "emms")
+(declare-function emms-player-simple-start "emms-player-simple")
+(declare-function emms-player-simple-stop "emms-player-simple")
+(defvar emms-player-simple-process-name)
+(defvar emms-player-cj/music-mpv)
+
+(defvar cj/music--mpv-regex
+  (concat "\\(?:\\." (regexp-opt cj/music-file-extensions) "\\'\\)"
+          "\\|\\`\\(?:https?\\|mms\\)://")
+  "Track names the subprocess mpv player handles: music files or stream URLs.")
+
+(defun cj/music--mpv-start (track)
+  "Play TRACK by running mpv with the track name as a direct argument."
+  (emms-player-simple-start (emms-track-name track)
+                            'emms-player-cj/music-mpv
+                            "mpv"
+                            (list "--no-video" "--no-config" "--really-quiet")))
+
+(defun cj/music--mpv-stop ()
+  "Stop the mpv subprocess."
+  (emms-player-simple-stop))
+
+(defun cj/music--mpv-playable-p (track)
+  "Return non-nil if the subprocess mpv player can play TRACK."
+  (and (executable-find "mpv")
+       (memq (emms-track-type track) '(file url))
+       (string-match cj/music--mpv-regex (emms-track-name track))))
+
+(defun cj/music--mpv-pause ()
+  "Pause the mpv subprocess in place by stopping it (SIGSTOP)."
+  (let ((proc (get-process emms-player-simple-process-name)))
+    (when (and proc (process-live-p proc))
+      (signal-process proc 'SIGSTOP))))
+
+(defun cj/music--mpv-resume ()
+  "Resume the paused mpv subprocess (SIGCONT)."
+  (let ((proc (get-process emms-player-simple-process-name)))
+    (when (and proc (process-live-p proc))
+      (signal-process proc 'SIGCONT))))
+
 ;;; Buffer-local state
 
 (defvar-local cj/music-playlist-file nil
@@ -843,7 +892,7 @@ For URL tracks: decoded URL."
   :commands (emms-mode-line-mode)
   :config
   (require 'emms-setup)
-  (require 'emms-player-mpv)
+  (require 'emms-player-simple)
   (require 'emms-playlist-mode)
   (require 'emms-source-file)
   (require 'emms-source-playlist)
@@ -852,8 +901,13 @@ For URL tracks: decoded URL."
   (setq emms-source-file-default-directory cj/music-root)
   (setq emms-playlist-default-major-mode 'emms-playlist-mode)
 
-  ;; Use MPV as player - MUST be set before emms-all
-  (setq emms-player-list '(emms-player-mpv))
+  ;; Use the reliable subprocess mpv player (built above) - MUST be set before emms-all
+  (setq emms-player-cj/music-mpv
+        (emms-player #'cj/music--mpv-start #'cj/music--mpv-stop
+                     #'cj/music--mpv-playable-p))
+  (emms-player-set emms-player-cj/music-mpv 'pause #'cj/music--mpv-pause)
+  (emms-player-set emms-player-cj/music-mpv 'resume #'cj/music--mpv-resume)
+  (setq emms-player-list '(emms-player-cj/music-mpv))
 
   ;; Now initialize EMMS
   (emms-all)
@@ -862,17 +916,6 @@ For URL tracks: decoded URL."
   (emms-playing-time-display-mode -1)
   (emms-mode-line-mode -1)
 
-  ;; MPV configuration
-  ;; MPV supports both local files and stream URLs
-  (setq emms-player-mpv-parameters
-        '("--quiet" "--no-video" "--audio-display=no"))
-
-  ;; Update supported file types for mpv player
-  (setq emms-player-mpv-regexp
-        (concat "\\(?:\\`\\(?:https?\\|mms\\)://\\)\\|\\(?:\\."
-                (regexp-opt cj/music-file-extensions)
-                "\\'\\)"))
-
   ;; Keep cj/music-playlist-file in sync if playlist is cleared.
   ;; Ensure we don't stack duplicate advice on reload.
   (advice-remove 'emms-playlist-clear #'cj/music--after-playlist-clear)