[MSE][GStreamer] Skip waiting for preroll when audio sink is non-async

https://bugs.webkit.org/show_bug.cgi?id=262492

Reviewed by Alicia Boya Garcia.

When the audio sink is non-async, the GST_STATE_CHANGE_ASYNC change will never happen. Under
these circumstances, the asyncStateChangeDone() code will never run. This patch calls that
method manually, fixing the issue. The method has been now given a better name (didPreroll()),
which better expresses the semantics.

Original author: Pawel Lampe <pawel.lampe@gmail.com>

See: #1195

* Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.cpp:
(WebCore::MediaPlayerPrivateGStreamerMSE::doSeek): Manually call asyncStateChangeDone() when the audio sink is non-async.
* Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:
(WebCore::MediaPlayerPrivateGStreamer::handleMessage): asyncStateChangeDone() renamed to didPreroll().
* Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.h:
(WebCore::MediaPlayerPrivateGStreamer::didPreroll): Old asyncStateChangeDone().
(WebCore::MediaPlayerPrivateGStreamer::asyncStateChangeDone): Deleted.
* Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.cpp:
(WebCore::MediaPlayerPrivateGStreamerMSE::doSeek): asyncStateChangeDone() renamed to didPreroll().
(WebCore::MediaPlayerPrivateGStreamerMSE::didPreroll): Old asyncStateChangeDone().
(WebCore::MediaPlayerPrivateGStreamerMSE::asyncStateChangeDone): Deleted.
* Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.h:

Canonical link: https://commits.webkit.org/268845@main

Author: Scony

Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp

@@ -1835,7 +1835,7 @@ void MediaPlayerPrivateGStreamer::handleMessage(GstMessage* message)
 
         // The MediaPlayerPrivateGStreamer superclass now processes what it needs by calling updateStates() in handleMessage() for
         // GST_MESSAGE_STATE_CHANGED. However, subclasses still need to override asyncStateChangeDone() to do their own stuff.
-        asyncStateChangeDone();
+        didPreroll();
         break;
     case GST_MESSAGE_STATE_CHANGED: {
         GstState newState;

Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.h

@@ -501,7 +501,7 @@ class MediaPlayerPrivateGStreamer : public MediaPlayerPrivateInterface
 
     virtual void updateStates();
     void finishSeek();
-    virtual void asyncStateChangeDone() { }
+    virtual void didPreroll() { }
 
     void createGSTPlayBin(const URL&);
 

Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.cpp

@@ -259,7 +259,19 @@ bool MediaPlayerPrivateGStreamerMSE::doSeek(const MediaTime& position, float rat
     invalidateCachedPosition();
 
     // Notify MediaSource and have new frames enqueued (when they're available).
+
     m_mediaSource->seekToTime(m_seekTime);
+
+    if (m_player && !m_player->isVideoPlayer() && m_audioSink) {
+        gboolean audioSinkPerformsAsyncStateChanges;
+        g_object_get(m_audioSink.get(), "async", &audioSinkPerformsAsyncStateChanges, nullptr);
+        if (!audioSinkPerformsAsyncStateChanges) {
+            // If audio-only pipeline's sink is not performing async state changes
+            // we must simulate preroll right away as otherwise nothing will trigger it.
+            didPreroll();
+        }
+    }
+
     return true;
 }
 
@@ -310,7 +322,7 @@ void MediaPlayerPrivateGStreamerMSE::propagateReadyStateToPlayer()
         m_player->timeChanged();
 }
 
-void MediaPlayerPrivateGStreamerMSE::asyncStateChangeDone()
+void MediaPlayerPrivateGStreamerMSE::didPreroll()
 {
     ASSERT(GST_STATE(m_pipeline.get()) >= GST_STATE_PAUSED);
     // There are three circumstances in which a preroll can occur:

Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.h

@@ -79,7 +79,7 @@ class MediaPlayerPrivateGStreamerMSE : public MediaPlayerPrivateGStreamer {
 
     void setInitialVideoSize(const FloatSize&);
 
-    void asyncStateChangeDone() override;
+    void didPreroll() override;
 
     void startSource(const Vector<RefPtr<MediaSourceTrackGStreamer>>& tracks);
     WebKitMediaSrc* webKitMediaSrc() { return reinterpret_cast<WebKitMediaSrc*>(m_source.get()); }