demux: add a demuxer thread

This adds a thread to the demuxer which reads packets asynchronously.
It will do so until a configurable minimum packet queue size is
reached. (See options.rst additions.)

For now, the thread is disabled by default. There are some corner cases
that have to be fixed, such as fixing cache behavior with webradios.

Note that most interaction with the demuxer is still blocking, so if
e.g. network dies, the player will still freeze. But this change will
make it possible to remove most causes for freezing.

Most of the new code in demux.c actually consists of weird caches to
compensate for thread-safety issues (with the previously single-threaded
design), or to avoid blocking by having to wait on the demuxer thread.

Most of the changes in the player are due to the fact that we must not
access the source stream directly. the demuxer thread already accesses
it, and the stream stuff is not thread-safe.

For timeline stuff (like ordered chapters), we enable the thread for the
current segment only. We also clear its packet queue on seek, so that
the remaining (unconsumed) readahead buffer doesn't waste memory.

Keep in mind that insane subtitles (such as ASS typesetting muxed into
mkv files) will practically disable the readahead, because the total
queue size is considered when checking whether the minimum queue size
was reached.

1 files changed, 46 insertions, 18 deletions

diff --git a/player/loadfile.c b/player/loadfile.c
index e2a1e6e145..e1ffa5d783 100644
--- a/player/loadfile.c
+++ b/player/loadfile.c
@@ -221,10 +221,15 @@ static void print_stream(struct MPContext *mpctx, struct track *t)
     MP_INFO(mpctx, "%s\n", b);
 }
 
-static void print_file_properties(struct MPContext *mpctx)
+void update_demuxer_properties(struct MPContext *mpctx)
 {
     struct demuxer *demuxer = mpctx->master_demuxer;
-    if (demuxer->num_editions > 1) {
+    if (!demuxer)
+        return;
+    demux_update(demuxer);
+    int events = demuxer->events;
+    demuxer->events = 0;
+    if ((events & DEMUX_EVENT_INIT) && demuxer->num_editions > 1) {
         for (int n = 0; n < demuxer->num_editions; n++) {
             struct demux_edition *edition = &demuxer->editions[n];
             char b[128] = {0};
@@ -238,10 +243,20 @@ static void print_file_properties(struct MPContext *mpctx)
             MP_INFO(mpctx, "%s\n", b);
         }
     }
-    for (int t = 0; t < STREAM_TYPE_COUNT; t++) {
-        for (int n = 0; n < mpctx->num_tracks; n++)
-            if (mpctx->tracks[n]->type == t)
-                print_stream(mpctx, mpctx->tracks[n]);
+    if (events & DEMUX_EVENT_STREAMS) {
+        add_demuxer_tracks(mpctx, demuxer);
+        for (int t = 0; t < STREAM_TYPE_COUNT; t++) {
+            for (int n = 0; n < mpctx->num_tracks; n++)
+                if (mpctx->tracks[n]->type == t)
+                    print_stream(mpctx, mpctx->tracks[n]);
+        }
+    }
+    struct mp_tags *info = demuxer->metadata;
+    if ((events & DEMUX_EVENT_METADATA) && info->num_keys) {
+        MP_INFO(mpctx, "File tags:\n");
+        for (int n = 0; n < info->num_keys; n++)
+            MP_INFO(mpctx, " %s: %s\n", info->keys[n], info->values[n]);
+        mp_notify(mpctx, MPV_EVENT_METADATA_UPDATE, NULL);
     }
 }
 
@@ -311,6 +326,11 @@ bool timeline_set_part(struct MPContext *mpctx, int i, bool force)
     uninit_player(mpctx, INITIALIZED_VCODEC | (mpctx->opts->fixed_vo ? 0 : INITIALIZED_VO) | (mpctx->opts->gapless_audio ? 0 : INITIALIZED_AO) | INITIALIZED_ACODEC | INITIALIZED_SUB | INITIALIZED_SUB2);
     mpctx->stop_play = orig_stop_play;
 
+    if (mpctx->demuxer) {
+        demux_stop_thread(mpctx->demuxer);
+        demux_flush(mpctx->demuxer);
+    }
+
     mpctx->demuxer = n->source;
     mpctx->stream = mpctx->demuxer->stream;
 
@@ -333,6 +353,9 @@ bool timeline_set_part(struct MPContext *mpctx, int i, bool force)
     }
     reselect_demux_streams(mpctx);
 
+    if (mpctx->demuxer && mpctx->opts->demuxer_thread)
+        demux_start_thread(mpctx->demuxer);
+
     return true;
 }
 
@@ -364,6 +387,7 @@ static int find_new_tid(struct MPContext *mpctx, enum stream_type t)
 }
 
 static struct track *add_stream_track(struct MPContext *mpctx,
+                                      struct demuxer *demuxer,
                                       struct sh_stream *stream,
                                       bool under_timeline)
 {
@@ -383,7 +407,7 @@ static struct track *add_stream_track(struct MPContext *mpctx,
         .attached_picture = stream->attached_picture != NULL,
         .lang = stream->lang,
         .under_timeline = under_timeline,
-        .demuxer = stream->demuxer,
+        .demuxer = demuxer,
         .stream = stream,
     };
     MP_TARRAY_APPEND(mpctx, mpctx->tracks, mpctx->num_tracks, track);
@@ -398,7 +422,7 @@ static struct track *add_stream_track(struct MPContext *mpctx,
 void add_demuxer_tracks(struct MPContext *mpctx, struct demuxer *demuxer)
 {
     for (int n = 0; n < demuxer->num_streams; n++)
-        add_stream_track(mpctx, demuxer->streams[n], !!mpctx->timeline);
+        add_stream_track(mpctx, demuxer, demuxer->streams[n], !!mpctx->timeline);
 }
 
 // Result numerically higher => better match. 0 == no match.
@@ -651,9 +675,11 @@ static void open_subtitles_from_options(struct MPContext *mpctx)
         void *tmp = talloc_new(NULL);
         char *base_filename = mpctx->filename;
         char *stream_filename = NULL;
-        if (stream_control(mpctx->stream, STREAM_CTRL_GET_BASE_FILENAME,
-                           &stream_filename) > 0)
-            base_filename = talloc_steal(tmp, stream_filename);
+        if (mpctx->demuxer) {
+            if (demux_stream_control(mpctx->demuxer, STREAM_CTRL_GET_BASE_FILENAME,
+                                     &stream_filename) > 0)
+                base_filename = talloc_steal(tmp, stream_filename);
+        }
         struct subfn *list = find_text_subtitles(mpctx->global, base_filename);
         talloc_steal(tmp, list);
         for (int i = 0; list && list[i].fname; i++) {
@@ -703,7 +729,7 @@ static struct track *open_external_file(struct MPContext *mpctx, char *filename,
     for (int n = 0; n < demuxer->num_streams; n++) {
         struct sh_stream *sh = demuxer->streams[n];
         if (sh->type == filter) {
-            struct track *t = add_stream_track(mpctx, sh, false);
+            struct track *t = add_stream_track(mpctx, demuxer, sh, false);
             t->is_external = true;
             t->title = talloc_strdup(t, disp_filename);
             t->external_filename = talloc_strdup(t, filename);
@@ -1160,6 +1186,11 @@ goto_reopen_demuxer: ;
     }
     reselect_demux_streams(mpctx);
 
+    update_demuxer_properties(mpctx);
+
+    if (mpctx->demuxer && opts->demuxer_thread)
+        demux_start_thread(mpctx->demuxer);
+
     if (mpctx->current_track[0][STREAM_VIDEO] &&
         mpctx->current_track[0][STREAM_VIDEO]->attached_picture)
     {
@@ -1167,9 +1198,6 @@ goto_reopen_demuxer: ;
             "Displaying attached picture. Use --no-audio-display to prevent this.\n");
     }
 
-    demux_info_update(mpctx->master_demuxer);
-    print_file_properties(mpctx);
-
 #if HAVE_ENCODING
     if (mpctx->encode_lavc_ctx && mpctx->current_track[0][STREAM_VIDEO])
         encode_lavc_expect_stream(mpctx->encode_lavc_ctx, AVMEDIA_TYPE_VIDEO);
@@ -1189,11 +1217,11 @@ goto_reopen_demuxer: ;
     //==================== START PLAYING =======================
 
     if (!mpctx->d_video && !mpctx->d_audio) {
-        struct stream *s = mpctx->stream;
+        struct demuxer *d = mpctx->demuxer;
         MP_FATAL(mpctx, "No video or audio streams selected.\n");
-        if (s->uncached_type == STREAMTYPE_DVB) {
+        if (d->stream->uncached_type == STREAMTYPE_DVB) {
             int dir = mpctx->last_dvb_step;
-            if (stream_control(s, STREAM_CTRL_DVB_STEP_CHANNEL, &dir) > 0)
+            if (demux_stream_control(d, STREAM_CTRL_DVB_STEP_CHANNEL, &dir) > 0)
                 mpctx->stop_play = PT_RELOAD_DEMUXER;
         }
         goto terminate_playback;