fix seek issue

PLAN.md

@@ -59,10 +59,13 @@ playback continues locally and the event is logged; clients do not reconnect.
 6. Any connected client receives the event and sends the corresponding JSON IPC
    command to its local MPV instance.
 
-Remote seeks use a serialized, acknowledged transaction: disable delivery of
+Remote seeks use a serialized transaction: disable delivery of the `seek`
-the `seek` event for the IPC connection, apply an `absolute+exact` seek, then
+event for the IPC connection, apply an `absolute+exact` seek, wait for mpv's
-re-enable the event even when the seek fails. This prevents remote seeks from
+`playback-restart` completion event, then re-enable the `seek` event even when
-being reported as new local seeks and looping through the server.
+the operation fails. A successful command reply alone is not a completion
+barrier because mpv can deliver seek effects afterward. Keeping delivery
+disabled through completion prevents remote seeks from being reported as new
+local seeks and looping through the server.
 
 **Example cli command to run MPV**
 

README.md

@@ -71,10 +71,13 @@ triggering ID to relayed events. Server and client terminals log play, pause,
 and seek actions with that ID; the triggering client is marked with `(you)` in
 its own terminal.
 
-Remote seeks are applied using an acknowledged mpv IPC transaction: seek event
+Remote seeks are applied using an mpv IPC transaction: seek event delivery is
-delivery is disabled for this IPC connection, an exact absolute seek is sent,
+disabled for this IPC connection, an exact absolute seek is sent, and the
-and event delivery is restored even if the seek fails. This prevents a remote
+client waits for mpv's `playback-restart` completion event before restoring
-seek from being mistaken for a new local seek and sent back indefinitely.
+seek event delivery. A command reply can arrive before the seek effects, so it
+is not sufficient as the end of the suppression window. Event delivery is
+still restored if the operation fails. This prevents a remote seek from being
+mistaken for a new local seek and sent back indefinitely.
 
 ## Prototype limitations
 

SEEK.md

@@ -0,0 +1,104 @@
+# seek issue
+
+When seeking (when video is paused, or being played) the video stutters and has clearly some feedback loop between clients.
+Analyze the code and find a fix.
+
+# client output
+
+```sh
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.848 seconds
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.848 seconds
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.848 seconds
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.848 seconds
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.848 seconds
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.848 seconds
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.848 seconds
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.848 seconds
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.848 seconds
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.848 seconds
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.848 seconds
+client: client 2 (you) played
+client: client 1 sought to 1766.848 seconds
+client: client 2 (you) sought to 1766.890 seconds
+client: client 1 sought to 1766.932 seconds
+client: client 2 (you) sought to 1766.974 seconds
+client: client 1 sought to 1767.015 seconds
+client: client 2 (you) sought to 1767.057 seconds
+client: client 1 sought to 1767.099 seconds
+client: client 2 (you) sought to 1767.140 seconds
+client: client 1 sought to 1767.182 seconds
+client: client 2 (you) sought to 1767.224 seconds
+client: client 1 sought to 1767.266 seconds
+client: client 2 (you) sought to 1767.307 seconds
+client: client 1 sought to 1767.349 seconds
+client: client 2 (you) paused
+client: client 2 (you) played
+client: client 2 (you) paused
+client: client 2 (you) played
+client: client 2 (you) paused
+client: mpv IPC connection closed
+client: server connection lost (mpv exited); playback will continue
+client: mpv exited with status 15
+```
+
+# server output
+
+```sh
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.848 seconds
+server: client 2 played
+server: client 1 sought to 1766.848 seconds
+server: client 2 sought to 1766.890 seconds
+server: client 1 sought to 1766.932 seconds
+server: client 2 sought to 1766.974 seconds
+server: client 1 sought to 1767.015 seconds
+server: client 2 sought to 1767.057 seconds
+server: client 1 sought to 1767.099 seconds
+server: client 2 sought to 1767.140 seconds
+server: client 1 sought to 1767.182 seconds
+server: client 2 sought to 1767.224 seconds
+server: client 1 sought to 1767.266 seconds
+server: client 2 sought to 1767.307 seconds
+server: client 1 sought to 1767.349 seconds
+server: client 2 paused
+server: client 2 played
+server: client 2 paused
+server: client 2 played
+server: client 2 paused
+server: client 2 disconnected (connection closed)
+server: client 1 disconnected (connection closed)
+```

mpv.odin

@@ -26,6 +26,8 @@ Mpv_Connection :: struct {
 	pending_id:      i64,
 	pending_done:    bool,
 	pending_result:  Mpv_Command_Result,
+	remote_seek_waiting:   bool,
+	remote_seek_completed: bool,
 	closed:          bool,
 
 	client: ^Client_State,
@@ -136,10 +138,35 @@ mpv_apply_remote_seek :: proc(mpv: ^Mpv_Connection, position: f64) -> bool {
 
 	seek_command := fmt.aprintf(`["seek",%.6f,"absolute+exact"]`, position)
 	defer delete(seek_command)
+	sync.mutex_lock(&mpv.response_mutex)
+	mpv.remote_seek_waiting = true
+	mpv.remote_seek_completed = false
+	sync.mutex_unlock(&mpv.response_mutex)
 	seek_result := mpv_command_locked(mpv, seek_command)
+
+	seek_completed := false
+	sync.mutex_lock(&mpv.response_mutex)
+	if seek_result.success {
+		deadline_remaining := MPV_COMMAND_TIMEOUT
+		for !mpv.remote_seek_completed && !mpv.closed {
+			start := time.now()
+			if !sync.cond_wait_with_timeout(&mpv.response_cond, &mpv.response_mutex, deadline_remaining) {
+				break
+			}
+			elapsed := time.since(start)
+			if elapsed >= deadline_remaining {
+				break
+			}
+			deadline_remaining -= elapsed
+		}
+		seek_completed = mpv.remote_seek_completed
+	}
+	mpv.remote_seek_waiting = false
+	sync.mutex_unlock(&mpv.response_mutex)
+
 	enable_result := mpv_command_locked(mpv, `["enable_event","seek"]`)
 	reenabled = enable_result.success
-	return seek_result.success && enable_result.success
+	return seek_result.success && seek_completed && enable_result.success
 }
 
 mpv_set_pause :: proc(mpv: ^Mpv_Connection, paused: bool) -> bool {
@@ -223,6 +250,14 @@ mpv_handle_line :: proc(mpv: ^Mpv_Connection, line: string) {
 	if !event_ok {
 		return
 	}
+	if string(event_name) == "playback-restart" {
+		sync.mutex_lock(&mpv.response_mutex)
+		if mpv.remote_seek_waiting {
+			mpv.remote_seek_completed = true
+			sync.cond_broadcast(&mpv.response_cond)
+		}
+		sync.mutex_unlock(&mpv.response_mutex)
+	}
 	if mpv.client != nil {
 		client_on_mpv_event(mpv.client, string(event_name), object)
 	}

mpv_test.odin

@@ -11,6 +11,7 @@ Fake_Mpv :: struct {
 	fd:       posix.FD,
 	received: [3]string,
 	fail_seek: bool,
+	enable_before_restart: bool,
 }
 
 fake_mpv_read_line :: proc(fd: posix.FD, buffer: []byte) -> (line: string, ok: bool) {
@@ -46,6 +47,14 @@ fake_mpv_loop :: proc(data: rawptr) {
 		)
 		_ = mpv_send_all(fake.fd, response)
 		delete(response)
+		if index == 1 && error_name == "success" {
+			poll_fd := posix.pollfd {
+				fd     = fake.fd,
+				events = {.IN},
+			}
+			fake.enable_before_restart = posix.poll(&poll_fd, 1, 50) > 0
+			_ = mpv_send_all(fake.fd, "{\"event\":\"playback-restart\"}\n")
+		}
 	}
 }
 
@@ -83,6 +92,7 @@ remote_seek_masks_and_restores_seek_events :: proc(t: ^testing.T) {
 	testing.expect(t, strings.contains(fake.received[0], `"disable_event","seek"`))
 	testing.expect(t, strings.contains(fake.received[1], `"seek",42.500000,"absolute+exact"`))
 	testing.expect(t, strings.contains(fake.received[2], `"enable_event","seek"`))
+	testing.expect(t, !fake.enable_before_restart)
 	for line in fake.received {
 		delete(line)
 	}