Handle QMediaPlayer outputs corner cases

- Clean-up the video sink frame after stop, QMediaPlayer deleting,
  and after setting new media.
- ensure no frames lost if change QVideoSink
- ensure no frames sent after changing of outputs.

The patch fixes problems with tests on Android, summarizing of
the related commits:
codereview.qt-project.org/c/qt/qtmultimedia/+/472214
codereview.qt-project.org/c/qt/qtmultimedia/+/470890
codereview.qt-project.org/c/qt/qtmultimedia/+/472052

Users want to have flush mode customization as it was it Qt5.
It might be added in 6.6 afterwards.

Fixes: QTBUG-112173
Task-number: QTBUG-111912
Change-Id: I0e4d34de06fcf23adf8a5736cbff4119478e9baf
Reviewed-by: Lars Knoll <lars@knoll.priv.no>

9 files changed, 98 insertions, 8 deletions

diff --git a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegaudiorenderer.cpp b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegaudiorenderer.cpp
index e44736c91..f1aa545eb 100644
--- a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegaudiorenderer.cpp
+++ b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegaudiorenderer.cpp
@@ -37,6 +37,11 @@ AudioRenderer::AudioRenderer(const TimeController &tc, QAudioOutput *output)
     }
 }
 
+void AudioRenderer::setOutput(QAudioOutput *output)
+{
+    setOutputInternal(m_output, output, [this](QAudioOutput *) { onDeviceChanged(); });
+}
+
 AudioRenderer::~AudioRenderer()
 {
     freeOutput();
diff --git a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegaudiorenderer_p.h b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegaudiorenderer_p.h
index b5aef8a71..594af6edb 100644
--- a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegaudiorenderer_p.h
+++ b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegaudiorenderer_p.h
@@ -35,6 +35,8 @@ class AudioRenderer : public Renderer
 public:
     AudioRenderer(const TimeController &tc, QAudioOutput *output);
 
+    void setOutput(QAudioOutput *output);
+
     ~AudioRenderer() override;
 
 protected:
diff --git a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegrenderer_p.h b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegrenderer_p.h
index e0ff9072f..784ab7891 100644
--- a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegrenderer_p.h
+++ b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegrenderer_p.h
@@ -77,6 +77,20 @@ protected:
 
     std::chrono::microseconds frameDelay(const Frame &frame) const;
 
+    template<typename Output, typename ChangeHandler>
+    void setOutputInternal(QPointer<Output> &actual, Output *desired, ChangeHandler &&changeHandler)
+    {
+        const auto connectionType = thread() == QThread::currentThread()
+                ? Qt::AutoConnection
+                : Qt::BlockingQueuedConnection;
+        auto doer = [desired, changeHandler, &actual]() {
+            const auto prev = std::exchange(actual, desired);
+            if (prev != desired)
+                changeHandler(prev);
+        };
+        QMetaObject::invokeMethod(this, doer, connectionType);
+    }
+
 private:
     void doNextStep() override;
 
diff --git a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegsubtitlerenderer.cpp b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegsubtitlerenderer.cpp
index 4e86ed482..789c9b53b 100644
--- a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegsubtitlerenderer.cpp
+++ b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegsubtitlerenderer.cpp
@@ -15,6 +15,14 @@ SubtitleRenderer::SubtitleRenderer(const TimeController &tc, QVideoSink *sink)
 {
 }
 
+void SubtitleRenderer::setOutput(QVideoSink *sink, bool cleanPrevSink)
+{
+    setOutputInternal(m_sink, sink, [cleanPrevSink](QVideoSink *prev) {
+        if (prev && cleanPrevSink)
+            prev->setSubtitleText({});
+    });
+}
+
 SubtitleRenderer::~SubtitleRenderer()
 {
     if (m_sink)
diff --git a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegsubtitlerenderer_p.h b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegsubtitlerenderer_p.h
index 146269fc3..972e152b4 100644
--- a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegsubtitlerenderer_p.h
+++ b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegsubtitlerenderer_p.h
@@ -30,6 +30,8 @@ public:
 
     ~SubtitleRenderer() override;
 
+    void setOutput(QVideoSink *sink, bool cleanPrevSink = false);
+
 protected:
     RenderingResult renderInternal(Frame frame) override;
 
diff --git a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegvideorenderer.cpp b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegvideorenderer.cpp
index 72ae0881f..2ad591c30 100644
--- a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegvideorenderer.cpp
+++ b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegvideorenderer.cpp
@@ -14,13 +14,23 @@ VideoRenderer::VideoRenderer(const TimeController &tc, QVideoSink *sink)
 {
 }
 
+void VideoRenderer::setOutput(QVideoSink *sink, bool cleanPrevSink)
+{
+    setOutputInternal(m_sink, sink, [cleanPrevSink](QVideoSink *prev) {
+        if (prev && cleanPrevSink)
+            prev->setVideoFrame({});
+    });
+}
+
 VideoRenderer::RenderingResult VideoRenderer::renderInternal(Frame frame)
 {
-    if (!frame.isValid())
+    if (!m_sink)
         return {};
 
-    if (!m_sink)
+    if (!frame.isValid()) {
+        m_sink->setVideoFrame({});
         return {};
+    }
 
     //        qCDebug(qLcVideoRenderer) << "RHI:" << accel.isNull() << accel.rhi() << sink->rhi();
 
diff --git a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegvideorenderer_p.h b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegvideorenderer_p.h
index e604af9f8..a229df495 100644
--- a/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegvideorenderer_p.h
+++ b/src/plugins/multimedia/ffmpeg/playbackengine/qffmpegvideorenderer_p.h
@@ -28,6 +28,8 @@ class VideoRenderer : public Renderer
 public:
     VideoRenderer(const TimeController &tc, QVideoSink *sink);
 
+    void setOutput(QVideoSink *sink, bool cleanPrevSink = false);
+
 protected:
     RenderingResult renderInternal(Frame frame) override;
 
diff --git a/src/plugins/multimedia/ffmpeg/qffmpegplaybackengine.cpp b/src/plugins/multimedia/ffmpeg/qffmpegplaybackengine.cpp
index c9c4f20f2..06215294d 100644
--- a/src/plugins/multimedia/ffmpeg/qffmpegplaybackengine.cpp
+++ b/src/plugins/multimedia/ffmpeg/qffmpegplaybackengine.cpp
@@ -50,6 +50,8 @@ PlaybackEngine::PlaybackEngine()
 
 PlaybackEngine::~PlaybackEngine() {
     qCDebug(qLcPlaybackEngine) << "Delete PlaybackEngine";
+
+    finalizeOutputs();
     forEachExistingObject([](auto &object) { object.reset(); });
     deleteFreeThreads();
 }
@@ -114,8 +116,10 @@ void PlaybackEngine::setState(QMediaPlayer::PlaybackState state) {
 
     const auto prevState = std::exchange(m_state, state);
 
-    if (m_state == QMediaPlayer::StoppedState)
+    if (m_state == QMediaPlayer::StoppedState) {
+        finalizeOutputs();
         finilizeTime(0);
+    }
 
     if (prevState == QMediaPlayer::StoppedState || m_state == QMediaPlayer::StoppedState)
         recreateObjects();
@@ -438,8 +442,7 @@ void PlaybackEngine::deleteFreeThreads() {
 
 bool PlaybackEngine::setMedia(const QUrl &media, QIODevice *stream)
 {
-    forEachExistingObject([](auto &object) { object.reset(); });
-    deleteFreeThreads();
+    stop();
 
     m_codecs = {};
 
@@ -448,14 +451,21 @@ bool PlaybackEngine::setMedia(const QUrl &media, QIODevice *stream)
         return false;
     }
 
-    forceUpdate();
     return true;
 }
 
 void PlaybackEngine::setVideoSink(QVideoSink *sink)
 {
-    if (std::exchange(m_videoSink, sink) != sink)
+    auto prev = std::exchange(m_videoSink, sink);
+    if (prev == sink)
+        return;
+
+    updateActiveVideoOutput(sink);
+
+    if (!sink || !prev) {
+        // might need some improvements
         forceUpdate();
+    }
 }
 
 void PlaybackEngine::setAudioSink(QPlatformAudioOutput *output) {
@@ -464,8 +474,16 @@ void PlaybackEngine::setAudioSink(QPlatformAudioOutput *output) {
 
 void PlaybackEngine::setAudioSink(QAudioOutput *output)
 {
-    if (std::exchange(m_audioOutput, output) != output)
+    auto prev = std::exchange(m_audioOutput, output);
+    if (prev == output)
+        return;
+
+    updateActiveAudioOutput(output);
+
+    if (!output || !prev) {
+        // might need some improvements
         forceUpdate();
+    }
 }
 
 qint64 PlaybackEngine::currentPosition(bool topPos) const {
@@ -515,6 +533,29 @@ void PlaybackEngine::finilizeTime(qint64 pos)
     m_timeController.sync(pos);
     m_currentLoopOffset = {};
 }
+
+void PlaybackEngine::finalizeOutputs()
+{
+    updateActiveAudioOutput(nullptr);
+    updateActiveVideoOutput(nullptr, true);
+}
+
+void PlaybackEngine::updateActiveAudioOutput(QAudioOutput *output)
+{
+    if (auto renderer =
+                qobject_cast<AudioRenderer *>(m_renderers[QPlatformMediaPlayer::AudioStream].get()))
+        renderer->setOutput(output);
+}
+
+void PlaybackEngine::updateActiveVideoOutput(QVideoSink *sink, bool cleanOutput)
+{
+    if (auto renderer = qobject_cast<SubtitleRenderer *>(
+                m_renderers[QPlatformMediaPlayer::SubtitleStream].get()))
+        renderer->setOutput(sink, cleanOutput);
+    if (auto renderer =
+                qobject_cast<VideoRenderer *>(m_renderers[QPlatformMediaPlayer::VideoStream].get()))
+        renderer->setOutput(sink, cleanOutput);
+}
 }
 
 QT_END_NAMESPACE
diff --git a/src/plugins/multimedia/ffmpeg/qffmpegplaybackengine_p.h b/src/plugins/multimedia/ffmpeg/qffmpegplaybackengine_p.h
index 4a61efa2f..2e39cf9cf 100644
--- a/src/plugins/multimedia/ffmpeg/qffmpegplaybackengine_p.h
+++ b/src/plugins/multimedia/ffmpeg/qffmpegplaybackengine_p.h
@@ -129,6 +129,10 @@ protected: // objects managing
 
     virtual RendererPtr createRenderer(QPlatformMediaPlayer::TrackType trackType);
 
+    void updateActiveAudioOutput(QAudioOutput *output);
+
+    void updateActiveVideoOutput(QVideoSink *sink, bool cleanOutput = false);
+
 private:
     void createStreamAndRenderer(QPlatformMediaPlayer::TrackType trackType);
 
@@ -168,6 +172,8 @@ private:
 
     void finilizeTime(qint64 pos);
 
+    void finalizeOutputs();
+
 private:
     TimeController m_timeController;