SCI32: Fix VMD playback stuttering when kEventFlagToFrame is used

For example, Shivers room 932 when subtitles are enabled.

2 files changed, 16 insertions, 4 deletions

diff --git a/engines/sci/graphics/video32.cpp b/engines/sci/graphics/video32.cpp
index 5f3a7a38a0..e44c159c1d 100644
--- a/engines/sci/graphics/video32.cpp
+++ b/engines/sci/graphics/video32.cpp
@@ -487,6 +487,7 @@ VMDPlayer::VMDPlayer(SegManager *segMan, EventManager *eventMan) :
 
 	_isOpen(false),
 	_isInitialized(false),
+	_yieldFrame(0),
 	_yieldInterval(0),
 	_lastYieldedFrameNo(0),
 
@@ -612,12 +613,12 @@ VMDPlayer::VMDStatus VMDPlayer::getStatus() const {
 VMDPlayer::EventFlags VMDPlayer::kernelPlayUntilEvent(const EventFlags flags, const int16 lastFrameNo, const int16 yieldInterval) {
 	assert(lastFrameNo >= -1);
 
-	const int32 maxFrameNo = (int32)(_decoder->getFrameCount() - 1);
+	const int32 maxFrameNo = _decoder->getFrameCount() - 1;
 
-	if ((flags & kEventFlagToFrame) && lastFrameNo > 0) {
-		_decoder->setEndFrame(MIN<int32>(lastFrameNo, maxFrameNo));
+	if (flags & kEventFlagToFrame) {
+		_yieldFrame = MIN<int32>(lastFrameNo, maxFrameNo);
 	} else {
-		_decoder->setEndFrame(maxFrameNo);
+		_yieldFrame = maxFrameNo;
 	}
 
 	if (flags & kEventFlagYieldToVM) {
@@ -755,6 +756,11 @@ VMDPlayer::EventFlags VMDPlayer::playUntilEvent(const EventFlags flags) {
 
 		const int currentFrameNo = _decoder->getCurFrame();
 
+		if (currentFrameNo == _yieldFrame) {
+			stopFlag = kEventFlagEnd;
+			break;
+		}
+
 		if (_yieldInterval > 0 &&
 			currentFrameNo != _lastYieldedFrameNo &&
 			(currentFrameNo % _yieldInterval) == 0
diff --git a/engines/sci/graphics/video32.h b/engines/sci/graphics/video32.h
index 75b8fb2d21..c3ae891c2e 100644
--- a/engines/sci/graphics/video32.h
+++ b/engines/sci/graphics/video32.h
@@ -326,6 +326,12 @@ private:
 	bool _isInitialized;
 
 	/**
+	 * For VMDs played with the `kEventFlagToFrame` flag,
+	 * the target frame for yielding back to the SCI VM.
+	 */
+	int32 _yieldFrame;
+
+	/**
 	 * For VMDs played with the `kEventFlagYieldToVM` flag,
 	 * the number of frames that should be rendered until
 	 * yielding back to the SCI VM.