Scale background playback speed by song rate. This sync isn't very accurate though (because of inaccurate playback rate code in sound library?)

stepmania/NEWS

@@ -44,6 +44,10 @@ NEW FEATURE:  Courses can be organized into group folders.  See
 	README-FIRST.html for details.
 NEW FEATURE:  Switch current theme from TitleMenu with L,L,L,R,R,R,L,R.
 NEW FEATURE:  Switch current announcer from TitleMenu with L,L,R,R,L,R,L,R.
+NEW FEATURE:  New parameters for background changes: rate, fade old, loop, 
+	rewind.
+CHANGE:  Background playback speed scaled by song rate, so movies stay in 
+	sync (although syncing isn't very accurate at some song rates).
 
 ----------------------- Version 3.01 ---------------------------
 CHANGE:  Simplified NoteSkin tap graphic format.  Old NoteSkins will need to 

stepmania/src/BGAnimationLayer.cpp

@@ -54,6 +54,9 @@ void BGAnimationLayer::Unload()
 void BGAnimationLayer::Init()
 {
 	Unload();
+
+	m_fUpdateRate = 1;
+
 //	m_bCycleColor = false;
 //	m_bCycleAlpha = false;
 //	m_Effect = EFFECT_STRETCH_STILL;
@@ -593,6 +596,8 @@ float BGAnimationLayer::GetMaxTweenTimeLeft() const
 
 void BGAnimationLayer::Update( float fDeltaTime )
 {
+	fDeltaTime *= m_fUpdateRate;
+
 	const float fSongBeat = GAMESTATE->m_fSongBeat;
 	
 	unsigned i;
@@ -869,6 +874,7 @@ void BGAnimationLayer::SetDiffuse( RageColor c )
 
 void BGAnimationLayer::GainingFocus( float fRate, bool bRewindMovie, bool bLoop )
 {
+	m_fUpdateRate = m_fRate;
 	m_Sprites.back()->GetTexture()->SetPlaybackRate(fRate);
 	if( bRewindMovie )
 		m_Sprites[0]->GetTexture()->SetPosition( 0 );

stepmania/src/BGAnimationLayer.h

@@ -96,6 +96,7 @@ protected:
 	
 	// common stuff
 	CString m_sCommand;
+	float m_fUpdateRate;	// get by GainingFocus
 
 	// stretch stuff
 	float m_fStretchTexCoordVelocityX;

stepmania/src/Background.cpp

@@ -323,6 +323,9 @@ void Background::LoadFromSong( Song* pSong )
 	// sort segments
 	SortBackgroundChangesArray( m_aBGChanges );
 
+	// scale all rates by the current music rate
+	for( unsigned i=0; i<m_aBGChanges.size(); i++ )
+		m_aBGChanges[i].m_fRate *= GAMESTATE->m_SongOptions.m_fMusicRate;
 
 
     for( map<CString,BGAnimation*>::iterator iter = m_BGAnimations.begin();