player: add an option to abort playback on partial init failures

This is probably what libmpv users want; and it also improves error
reporting (or we'd have to add a way to communicate such mid-playback
failures as events).

DOCS/client-api-changes.rst

@@ -28,6 +28,8 @@ API changes
  1.9    - add enum mpv_end_file_reason for mpv_event_end_file.reason
         - add MPV_END_FILE_REASON_ERROR and the mpv_event_end_file.error field
           for slightly better error reporting on playback failure
+        - add --stop-playback-on-init-failure option, and make it the default
+          behavior for libmpv only
  1.8    - add qthelper.hpp
  1.7    - add mpv_command_node(), mpv_command_node_async()
  1.6    - modify "core-idle" property behavior

DOCS/man/options.rst

@@ -252,6 +252,12 @@ Playback Control
 
         Without ``--hr-seek``, skipping will snap to keyframes.
 
+``--stop-playback-on-init-failure=<yes|no>``
+    Stop playback if either audio or video fails to initialize. Currently,
+    the default behavior is ``no`` for the command line player, but ``yes``
+    for libmpv. With ``no``, playback will continue in video-only or audio-only
+    mode if one of them fails. This doesn't affect playback of audio-only or
+    video-only files.
 
 Program Behavior
 ----------------

options/options.c

@@ -478,6 +478,8 @@ const m_option_t mp_opts[] = {
     OPT_STRING("stream-capture", stream_capture, M_OPT_FIXED | M_OPT_FILE),
     OPT_STRING("stream-dump", stream_dump, M_OPT_FIXED | M_OPT_FILE),
 
+    OPT_FLAG("stop-playback-on-init-failure", stop_playback_on_init_failure, 0),
+
     OPT_CHOICE_OR_INT("loop", loop_times, M_OPT_GLOBAL, 2, 10000,
                       ({"no", -1}, {"1", -1},
                        {"inf", 0})),

options/options.h

@@ -110,6 +110,7 @@ typedef struct MPOpts {
     int untimed;
     char *stream_capture;
     char *stream_dump;
+    int stop_playback_on_init_failure;
     int loop_times;
     int loop_file;
     int shuffle;

player/client.c

@@ -417,6 +417,7 @@ mpv_handle *mpv_create(void)
         mpv_set_option_string(ctx, "input-appleremote", "no");
         mpv_set_option_string(ctx, "input-media-keys", "no");
         mpv_set_option_string(ctx, "input-app-events", "no");
+        mpv_set_option_string(ctx, "stop-playback-on-init-failure", "yes");
     } else {
         mp_destroy(mpctx);
     }

player/loadfile.c

@@ -1091,7 +1091,7 @@ goto_reopen_demuxer: ;
         struct demuxer *d = mpctx->demuxer;
         MP_FATAL(mpctx, "No video or audio streams selected.\n");
         if (d->stream->uncached_type == STREAMTYPE_DVB) {
-            int dir = mpctx->last_dvb_step;
+            int  dir = mpctx->last_dvb_step;
             if (demux_stream_control(d, STREAM_CTRL_DVB_STEP_CHANNEL, &dir) > 0)
                 mpctx->stop_play = PT_RELOAD_DEMUXER;
         }

player/misc.c

@@ -189,8 +189,9 @@ void error_on_track(struct MPContext *mpctx, struct track *track)
             MP_INFO(mpctx, "Audio: no audio\n");
         if (track->type == STREAM_VIDEO)
             MP_INFO(mpctx, "Video: no video\n");
-        if (!mpctx->current_track[0][STREAM_AUDIO] &&
-            !mpctx->current_track[0][STREAM_VIDEO])
+        if (mpctx->opts->stop_playback_on_init_failure ||
+            (!mpctx->current_track[0][STREAM_AUDIO] &&
+             !mpctx->current_track[0][STREAM_VIDEO]))
         {
             mpctx->stop_play = PT_ERROR;
             if (mpctx->error_playing >= 0)