player: some further playloop cleanups

Handle --term-playing-msg at a better place.

Move MPV_EVENT_TICK hack into a separate function. Also add some words
to the client API that you shouldn't use it. (But better leave breaking
it for later.)

Handle --frames and frame_step differently. Remove the mess from the
playloop, and do it after frame display. Give up on the weird semantics
for audio-only mode (they didn't make sense anyway), and adjust the
manpage accordingly.

DOCS/man/input.rst

@@ -106,7 +106,7 @@ List of Input Commands
     ``revert_seek`` command itself.
 
 ``frame_step``
-    Play one frame, then pause.
+    Play one frame, then pause. Does nothing with audio-only playback.
 
 ``frame_back_step``
     Go back by one frame, then pause. Note that this can be very slow (it tries

DOCS/man/options.rst

@@ -919,11 +919,14 @@ OPTIONS
         Practical use of this feature is questionable. Disabled by default.
 
 ``--frames=<number>``
-    Play/convert only first ``<number>`` video frames, then quit. For audio
-    only, run ``<number>`` iteration of the playback loop, which is most likely
-    not what you want. (This behavior also applies to the corner case when there
-    are fewer video frames than ``<number>``, and audio is longer than the
-    video.)
+    Play/convert only first ``<number>`` video frames, then quit.
+
+    ``--frames=0`` loads the file, but immediately quits before initializing
+    playback. (Might be useful for scripts which just want to determine some
+    file properties.)
+
+    For audio-only playback, any value greater than 0 will quit playback
+    immediately after initialization. The value 0 works as with video.
 
 ``--fullscreen``, ``--fs``
     Fullscreen playback.

libmpv/client.h

@@ -919,8 +919,10 @@ typedef enum mpv_event_id {
      */
     MPV_EVENT_UNPAUSE           = 13,
     /**
-     * Sent every time after a video frame is displayed (or in lower frequency
-     * if there is no video, or playback is paused).
+     * Sent every time after a video frame is displayed. Note that currently,
+     * this will be sent in lower frequency if there is no video, or playback
+     * is paused - but that will be removed in the future, and it will be
+     * restricted to video frames only.
      */
     MPV_EVENT_TICK              = 14,
     /**

player/playloop.c

@@ -712,12 +712,20 @@ static void handle_backstep(struct MPContext *mpctx)
 static void handle_sstep(struct MPContext *mpctx)
 {
     struct MPOpts *opts = mpctx->opts;
-    if (opts->step_sec > 0 && !mpctx->stop_play && !mpctx->paused &&
-        mpctx->restart_complete)
-    {
+    if (mpctx->stop_play || !mpctx->restart_complete)
+        return;
+
+    if (opts->step_sec > 0 && !mpctx->paused) {
         set_osd_function(mpctx, OSD_FFW);
         queue_seek(mpctx, MPSEEK_RELATIVE, opts->step_sec, 0, true);
     }
+
+    if (mpctx->video_status >= STATUS_DRAINING) {
+        if (mpctx->max_frames >= 0)
+            mpctx->stop_play = PT_NEXT_ENTRY;
+        if (mpctx->step_frames > 0 && !mpctx->paused)
+            pause_player(mpctx);
+    }
 }
 
 static void handle_loop_file(struct MPContext *mpctx)
@@ -785,6 +793,17 @@ void handle_force_window(struct MPContext *mpctx, bool reconfig)
     }
 }
 
+// Potentially needed by some Lua scripts, which assume TICK always comes.
+static void handle_dummy_ticks(struct MPContext *mpctx)
+{
+    if (mpctx->video_status == STATUS_EOF || mpctx->paused) {
+        if (mp_time_sec() - mpctx->last_idle_tick > 0.5) {
+            mpctx->last_idle_tick = mp_time_sec();
+            mp_notify(mpctx, MPV_EVENT_TICK, NULL);
+        }
+    }
+}
+
 static double get_wakeup_period(struct MPContext *mpctx)
 {
     double sleeptime = 100.0; // infinite for all practical purposes
@@ -806,7 +825,6 @@ void run_playloop(struct MPContext *mpctx)
     struct MPOpts *opts = mpctx->opts;
     double endpts = get_play_end_pts(mpctx);
     bool end_is_new_segment = false;
-    int64_t shown_vframes = mpctx->shown_vframes;
 
 #if HAVE_ENCODING
     if (encode_lavc_didfail(mpctx->encode_lavc_ctx)) {
@@ -840,13 +858,6 @@ void run_playloop(struct MPContext *mpctx)
     fill_audio_out_buffers(mpctx, endpts);
     write_video(mpctx, endpts);
 
-    if (mpctx->video_status == STATUS_EOF || mpctx->paused) {
-        if (mp_time_sec() - mpctx->last_idle_tick > 0.5) {
-            mpctx->last_idle_tick = mp_time_sec();
-            mp_notify(mpctx, MPV_EVENT_TICK, NULL);
-        }
-    }
-
     // We always make sure audio and video buffers are filled before actually
     // starting playback. This code handles starting them at the same time.
     if (mpctx->audio_status >= STATUS_READY &&
@@ -856,7 +867,6 @@ void run_playloop(struct MPContext *mpctx)
             mpctx->video_status = STATUS_PLAYING;
             get_relative_time(mpctx);
             mpctx->sleeptime = 0;
-            shown_vframes -= 1; // make framestep think there was a new video frame
         }
         if (mpctx->audio_status == STATUS_READY)
             fill_audio_out_buffers(mpctx, endpts); // actually play prepared buffer
@@ -864,6 +874,13 @@ void run_playloop(struct MPContext *mpctx)
             mpctx->hrseek_active = false;
             mp_notify(mpctx, MPV_EVENT_PLAYBACK_RESTART, NULL);
             mpctx->restart_complete = true;
+            if (opts->playing_msg && !mpctx->playing_msg_shown) {
+                mpctx->playing_msg_shown = true;
+                char *msg =
+                    mp_property_expand_escaped_string(mpctx, opts->playing_msg);
+                MP_INFO(mpctx, "%s\n", msg);
+                talloc_free(msg);
+            }
         }
     }
 
@@ -876,6 +893,8 @@ void run_playloop(struct MPContext *mpctx)
         mpctx->playback_pts = a_pos;
     }
 
+    handle_dummy_ticks(mpctx);
+
     update_osd_msg(mpctx);
     update_subtitles(mpctx);
 
@@ -908,37 +927,7 @@ void run_playloop(struct MPContext *mpctx)
 
     handle_keep_open(mpctx);
 
-    if (!mpctx->stop_play && mpctx->restart_complete) {
-        bool new_frame_shown = shown_vframes < mpctx->shown_vframes;
-
-        // If no more video is available, one frame means one playloop iteration.
-        // Otherwise, one frame means one video frame.
-        if (mpctx->video_status == STATUS_EOF)
-            new_frame_shown = true;
-
-        if (opts->playing_msg && !mpctx->playing_msg_shown && new_frame_shown) {
-            mpctx->playing_msg_shown = true;
-            char *msg =
-                mp_property_expand_escaped_string(mpctx, opts->playing_msg);
-            MP_INFO(mpctx, "%s\n", msg);
-            talloc_free(msg);
-        }
-
-        if (mpctx->max_frames >= 0) {
-            if (new_frame_shown)
-                mpctx->max_frames--;
-            if (mpctx->max_frames <= 0)
-                mpctx->stop_play = PT_NEXT_ENTRY;
-        }
-
-        if (mpctx->step_frames > 0 && !mpctx->paused) {
-            if (new_frame_shown)
-                mpctx->step_frames--;
-            if (mpctx->step_frames == 0)
-                pause_player(mpctx);
-        }
-
-    }
+    handle_sstep(mpctx);
 
     handle_loop_file(mpctx);
 
@@ -960,8 +949,6 @@ void run_playloop(struct MPContext *mpctx)
 
     handle_backstep(mpctx);
 
-    handle_sstep(mpctx);
-
     handle_chapter_change(mpctx);
 
     handle_force_window(mpctx, false);
@@ -987,6 +974,7 @@ void idle_loop(struct MPContext *mpctx)
             handle_force_window(mpctx, true);
         }
         need_reinit = false;
+        handle_dummy_ticks(mpctx);
         int uninit = INITIALIZED_AO;
         if (!mpctx->opts->force_vo)
             uninit |= INITIALIZED_VO;

player/video.c

@@ -896,4 +896,16 @@ void write_video(struct MPContext *mpctx, double endpts)
 
     if (!mpctx->sync_audio_to_video)
         mpctx->video_status = STATUS_EOF;
+
+    if (mpctx->video_status != STATUS_EOF) {
+        if (mpctx->step_frames > 0) {
+            mpctx->step_frames--;
+            if (!mpctx->step_frames && !opts->pause)
+                pause_player(mpctx);
+        }
+        if (mpctx->max_frames == 0)
+            mpctx->stop_play = PT_NEXT_ENTRY;
+        if (mpctx->max_frames > 0)
+            mpctx->max_frames--;
+    }
 }