Fix single-image input with the FFmpeg Qt Media backend

src/videoframe.cpp

@@ -1,7 +1,7 @@
 /*
  * This file is part of Bino, a 3D video player.
  *
- * Copyright (C) 2022
+ * Copyright (C) 2022, 2023, 2024
  * Martin Lambers <[email protected]>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -27,14 +27,18 @@ VideoFrame::VideoFrame()
     update(Input_Unknown, Surround_Unknown, QVideoFrame(), false);
 }
 
+bool VideoFrame::isValid() const
+{
+    return (qframe.isValid() && qframe.pixelFormat() != QVideoFrameFormat::Format_Invalid);
+}
+
 void VideoFrame::update(InputMode im, SurroundMode sm, const QVideoFrame& frame, bool newSrc)
 {
     if (qframe.isMapped())
         qframe.unmap();
     qframe = frame;
 
-    bool valid = (qframe.isValid() && qframe.pixelFormat() != QVideoFrameFormat::Format_Invalid);
-    if (valid) {
+    if (isValid()) {
         subtitle = qframe.subtitleText();
         width = qframe.width();
         height = qframe.height();
@@ -172,7 +176,7 @@ void VideoFrame::reUpdate()
 
 void VideoFrame::invalidate()
 {
-    if (qframe.isValid())
+    if (isValid())
         update(Input_Unknown, Surround_Unknown, QVideoFrame(), false);
 }
 

src/videoframe.hpp

@@ -1,7 +1,7 @@
 /*
  * This file is part of Bino, a 3D video player.
  *
- * Copyright (C) 2022
+ * Copyright (C) 2022, 2023, 2024
  * Martin Lambers <[email protected]>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -87,6 +87,7 @@ Q_DECLARE_TR_FUNCTIONS(VideoFrame)
 
     VideoFrame();
 
+    bool isValid() const;
     void update(InputMode im, SurroundMode ts, const QVideoFrame& frame, bool newSrc);
     void reUpdate();
     void invalidate();

src/videosink.cpp

@@ -1,7 +1,7 @@
 /*
  * This file is part of Bino, a 3D video player.
  *
- * Copyright (C) 2022
+ * Copyright (C) 2022, 2023, 2024
  * Martin Lambers <[email protected]>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -32,7 +32,8 @@ VideoSink::VideoSink(VideoFrame* frame, VideoFrame* extFrame, bool* frameIsNew)
     frameIsNew(frameIsNew),
     needExtFrame(false),
     inputMode(Input_Unknown),
-    surroundMode(Surround_Unknown)
+    surroundMode(Surround_Unknown),
+    lastFrameWasValid(false)
 {
     connect(this, SIGNAL(videoFrameChanged(const QVideoFrame&)), this, SLOT(processNewFrame(const QVideoFrame&)));
 }
@@ -42,6 +43,7 @@ void VideoSink::newUrl(const QUrl& url, InputMode im, SurroundMode sm)
 {
     frameCounter = 0;
     fileFormatIsMPO = false;
+    lastFrameWasValid = false;
 
     LOG_DEBUG("initial input mode for %s: %s", qPrintable(url.toString()), inputModeToString(im));
     inputMode = im;
@@ -116,6 +118,16 @@ void VideoSink::newUrl(const QUrl& url, InputMode im, SurroundMode sm)
 
 void VideoSink::processNewFrame(const QVideoFrame& frame)
 {
+    if (!frame.isValid() && lastFrameWasValid) {
+        // keep showing the last frame of the current media; ignore that QtMultiMedia
+        // with the FFmpeg backend gives us an invalid frame as soon as the media stops
+        // (it does not do this with the GStreamer backend)
+        LOG_DEBUG("video sink gets invalid frame and ignores it since last frame of current media was valid");
+        return;
+    }
+    if (frame.isValid())
+        lastFrameWasValid = true;
+
     // Workaround a glitch in the MPO file format:
     // Gstreamer reads three frames from such files, the first two being the left
     // view and the last one being the right view.

src/videosink.hpp

@@ -1,7 +1,7 @@
 /*
  * This file is part of Bino, a 3D video player.
  *
- * Copyright (C) 2022
+ * Copyright (C) 2022, 2023, 2024
  * Martin Lambers <[email protected]>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -40,6 +40,7 @@ Q_OBJECT
     bool needExtFrame;    // flag to set in alternating stereo when extFrame is not filled yet
     InputMode inputMode;  // input mode of current media
     SurroundMode surroundMode; // surround mode of the current media
+    bool lastFrameWasValid; // last frame of current media was valid
 
     VideoSink(VideoFrame* frame, VideoFrame* extFrame, bool* frameIsNew);