player: add --track-auto-selection option

I imagine this is useful. Or maybe it isn't.

DOCS/interface-changes.rst

@@ -38,6 +38,8 @@ Interface changes
     - --lavfi-complex can now be set during runtime. If you set this in
       expectation it would be applied only after a reload, you might observe
       weird behavior.
+    - add --track-auto-selection to help with scripts/applications that
+      make exclusive use of --lavfi-complex.
  --- mpv 0.26.0 ---
     - remove remaining deprecated audio device options, like --alsa-device
       Some of them were removed in earlier releases.

DOCS/man/options.rst

@@ -76,6 +76,18 @@ Track Selection
     to ``auto`` (the default), mpv will choose the first edition declared as a
     default, or if there is no default, the first edition defined.
 
+``--track-auto-selection=<yes|no>``
+    Enable the default track auto-selection (default: yes). Enabling this will
+    make the player select streams according to ``--aid``, ``--alang``, and
+    others. If it is disabled, no tracks are selected. In addition, the player
+    will not exit if no tracks are selected, and wait instead (this wait mode
+    is similar to pausing, but the pause option is not set).
+
+    This is useful with ``--lavfi-complex``: you can start playback in this
+    mode, and then set select tracks at runtime by setting the filter graph.
+    Note that if ``--lavfi-complex`` is set before playback is started, the
+    referenced tracks are always selected.
+
 
 Playback Control
 ----------------

options/options.c

@@ -361,6 +361,7 @@ const m_option_t mp_opts[] = {
     OPT_ALIAS("audio", "aid"),
     OPT_STRINGLIST("alang", stream_lang[STREAM_AUDIO], 0),
     OPT_STRINGLIST("slang", stream_lang[STREAM_SUB], 0),
+    OPT_FLAG("track-auto-selection", stream_auto_sel, 0),
 
     OPT_STRING("lavfi-complex", lavfi_complex, UPDATE_LAVFI_COMPLEX),
 
@@ -921,6 +922,7 @@ const struct MPOpts mp_default_opts = {
     .stream_id_ff = { [STREAM_AUDIO] = -1,
                       [STREAM_VIDEO] = -1,
                       [STREAM_SUB] = -1, },
+    .stream_auto_sel = 1,
     .audio_display = 1,
     .sub_visibility = 1,
     .sub_pos = 100,

options/options.h

@@ -212,6 +212,7 @@ typedef struct MPOpts {
     int stream_id[2][STREAM_TYPE_COUNT];
     int stream_id_ff[STREAM_TYPE_COUNT];
     char **stream_lang[STREAM_TYPE_COUNT];
+    int stream_auto_sel;
     int audio_display;
     char **display_tags;
     int sub_visibility;

player/loadfile.c

@@ -1269,7 +1269,7 @@ reopen_file:
             struct track *sel = NULL;
             bool taken = (t == STREAM_VIDEO && mpctx->vo_chain) ||
                          (t == STREAM_AUDIO && mpctx->ao_chain);
-            if (!taken)
+            if (!taken && opts->stream_auto_sel)
                 sel = select_default_track(mpctx, i, t);
             mpctx->current_track[i][t] = sel;
         }
@@ -1311,7 +1311,7 @@ reopen_file:
     reinit_audio_chain(mpctx);
     reinit_sub_all(mpctx);
 
-    if (!mpctx->vo_chain && !mpctx->ao_chain) {
+    if (!mpctx->vo_chain && !mpctx->ao_chain && opts->stream_auto_sel) {
         MP_FATAL(mpctx, "No video or audio streams selected.\n");
         mpctx->error_playing = MPV_ERROR_NOTHING_TO_PLAY;
         goto terminate_playback;