[rhythmbox] xfade: improve handling of resumption after buffering

[Jonathan Matthew <jmatthew src gnome org>]

commit 59fe56f7c7937adb6cf0bf09273b7232c014f7c2
Author: Jonathan Matthew <jonathan d14n org>
Date:   Sat Apr 24 21:20:36 2021 +1000

    xfade: improve handling of resumption after buffering
    
    When we receive a buffering message indicating a stream is now buffered,
    it's either already blocked, in which case we can link it and resume
    immediately, or not yet blocked, which means we have to wait for the
    pad block callback to link it.

 backends/gstreamer/rb-player-gst-xfade.c | 44 ++++++++++++++++++++++++--------
 1 file changed, 34 insertions(+), 10 deletions(-)
---
diff --git a/backends/gstreamer/rb-player-gst-xfade.c b/backends/gstreamer/rb-player-gst-xfade.c
index c780f8495..4862b9320 100644
--- a/backends/gstreamer/rb-player-gst-xfade.c
+++ b/backends/gstreamer/rb-player-gst-xfade.c
@@ -384,6 +384,7 @@ typedef struct
 
 static void adjust_stream_base_time (RBXFadeStream *stream);
 static gboolean actually_start_stream (RBXFadeStream *stream, GError **error);
+static GstPadProbeReturn stream_src_blocked_cb (GstPad *pad, GstPadProbeInfo *info, RBXFadeStream *stream);
 
 static void rb_xfade_stream_class_init (RBXFadeStreamClass *klass);
 
@@ -1869,6 +1870,7 @@ rb_player_gst_xfade_bus_cb (GstBus *bus, GstMessage *message, RBPlayerGstXFade *
        {
                const GstStructure *s;
                gint progress;
+               gboolean resume;
 
                s = gst_message_get_structure (message);
                if (!gst_structure_get_int (s, "buffer-percent", &progress)) {
@@ -1910,20 +1912,32 @@ rb_player_gst_xfade_bus_cb (GstBus *bus, GstMessage *message, RBPlayerGstXFade *
                                break;
 
                        default:
-                               /* make sure we're not going to remove it */
                                g_mutex_lock (&stream->lock);
-                               if (stream->block_probe_id != 0) {
-                                       gst_pad_remove_probe (stream->src_pad, stream->block_probe_id);
-                                       stream->block_probe_id = 0;
-                                       stream->needs_unlink = FALSE;
+                               stream->needs_unlink = FALSE;
+                               resume = stream->src_blocked;
+                               if (resume == FALSE) {
+                                       rb_debug ("stream %s is buffered, waiting for block callback to 
resume", stream->uri);
+                                       if (stream->block_probe_id != 0) {
+                                               gst_pad_remove_probe (stream->src_pad, 
stream->block_probe_id);
+                                               stream->block_probe_id = 0;
+                                       }
+                                       stream->block_probe_id =
+                                           gst_pad_add_probe (stream->src_pad,
+                                                              GST_PAD_PROBE_TYPE_BLOCK_DOWNSTREAM,
+                                                              (GstPadProbeCallback) stream_src_blocked_cb,
+                                                              stream,
+                                                              NULL);
                                }
                                g_mutex_unlock (&stream->lock);
 
-                               rb_debug ("stream %s is buffered, resuming", stream->uri);
-                               link_and_unblock_stream (stream, &error);
-                               if (error) {
-                                       g_warning ("couldn't restart newly buffered stream: %s", 
error->message);
-                                       g_clear_error (&error);
+                               if (resume) {
+                                       rb_debug ("stream %s is buffered and already blocked, resuming", 
stream->uri);
+
+                                       link_and_unblock_stream (stream, &error);
+                                       if (error) {
+                                               g_warning ("couldn't restart newly buffered stream: %s", 
error->message);
+                                               g_clear_error (&error);
+                                       }
                                }
                                break;
                        }
@@ -2561,6 +2575,7 @@ stream_src_blocked_cb (GstPad *pad, GstPadProbeInfo *info, RBXFadeStream *stream
 {
        GError *error = NULL;
        gboolean start_stream = FALSE;
+       gboolean link_stream = FALSE;
        GstElement *src;
        GstQuery *query;
 
@@ -2613,6 +2628,11 @@ stream_src_blocked_cb (GstPad *pad, GstPadProbeInfo *info, RBXFadeStream *stream
                rb_debug ("stream %s is prerolled, need to start it", stream->uri);
                start_stream = TRUE;
                break;
+       case PLAYING:
+       case FADING_IN:
+               rb_debug ("stream %s already playing, unblocking", stream->uri);
+               link_stream = TRUE;
+               break;
        default:
                rb_debug ("didn't expect to get preroll completion callback in this state (%d)", 
stream->state);
                break;
@@ -2625,6 +2645,10 @@ stream_src_blocked_cb (GstPad *pad, GstPadProbeInfo *info, RBXFadeStream *stream
                if (actually_start_stream (stream, &error) == FALSE) {
                        emit_stream_error (stream, error);
                }
+       } else if (link_stream == TRUE) {
+               if (link_and_unblock_stream (stream, &error) == FALSE) {
+                       emit_stream_error (stream, error);
+               }
        }
 
        return GST_PAD_PROBE_OK;