Fix: don't chop off the first 26ms of each MP3 (but don't change sync,

either).

stepmania/src/RageSound.cpp

@@ -520,7 +520,7 @@ void RageSound::StopPlaying()
 	if(!playing)
 		return;
 
-	stopped_position = GetPositionSeconds();
+	stopped_position = GetPositionSecondsInternal();
 
 	/* Tell the sound manager to stop mixing this sound. */
 	SOUNDMAN->StopMixing(this);
@@ -555,7 +555,8 @@ float RageSound::GetLengthSeconds()
 	return len / 1000.f; /* ms -> secs */
 }
 
-float RageSound::GetPositionSeconds() const
+/* Get the position, not counting GetOffsetFix. */
+float RageSound::GetPositionSecondsInternal() const
 {
 	LockMut(SOUNDMAN->lock);
 
@@ -624,6 +625,13 @@ float RageSound::GetPositionSeconds() const
 	return GetPlaybackRate() * closest_position / float(samplerate());
 }
 
+float RageSound::GetPositionSeconds() const
+{
+	LOG->Trace("XXX fix %f", Sample->GetOffsetFix());
+	return GetPositionSecondsInternal() + Sample->GetOffsetFix();
+}
+
+
 bool RageSound::SetPositionSeconds( float fSeconds )
 {
 	return SetPositionSamples( fSeconds == -1? -1: int(fSeconds * samplerate()) );

stepmania/src/RageSound.h

@@ -132,6 +132,7 @@ private:
 
 	CString error;
 
+	float GetPositionSecondsInternal() const;
 	bool SetPositionSamples( int samples = -1 );
 	int GetData(char *buffer, int size);
 	void Fail(CString reason);

stepmania/src/RageSoundReader.h

@@ -10,6 +10,8 @@ protected:
 	void SetError(string e) const { error = e; }
 
 public:
+	virtual float GetOffsetFix() const { return 0; }
+	
 	virtual int GetLength() const = 0; /* ms */
 	virtual int GetLength_Fast() const { return GetLength(); } /* ms */
 	virtual int SetPosition_Accurate(int ms) = 0;

stepmania/src/RageSoundReader_MP3.cpp

@@ -604,12 +604,24 @@ SoundReader_FileReader::OpenResult RageSoundReader_MP3::Open( CString filename_
 
 	SampleRate = mad->Frame.header.samplerate;
 	mad->framelength = mad->Frame.header.duration;
-	this->Channels = 0;
+	this->Channels = MAD_NCHANNELS( &mad->Frame.header );
 
 	/* Since we've already decoded a frame, just synth it instead of rewinding
 	 * the stream. */
 	synth_output();
-	this->Channels = MAD_NCHANNELS( &mad->Frame.header );
+
+	/*
+	 * Hack: Old code was setting Channels = 0 before synth_output.  This caused
+	 * the first synthed frame to not be written to the output buffer, offsetting
+	 * the whole song by a buffer.  On one test song, it was 1152/44100, or 26ms.
+	 * This affects all MP3s.  We can't leave the bug in, since we need to handle
+	 * seeks properly, too.  So, let's make the offset to fix seeks available.
+	 *
+	 * This is negative: if we have 26ms of extra data, then song offsets are
+	 * fixed by subtracting 26ms.
+	 */
+
+	this->OffsetFix = - (float) mad->Synth.pcm.length / mad->Frame.header.samplerate;
 
     if(mad->length == -1)
     {

stepmania/src/RageSoundReader_MP3.h

@@ -11,6 +11,7 @@ class RageSoundReader_MP3: public SoundReader_FileReader
 public:
 	int SampleRate;
     int Channels;
+	float OffsetFix;
 
 	CString filename;
     FILE *rw;
@@ -40,6 +41,8 @@ public:
 	int SetPosition_Fast(int ms);
 	int Read(char *buf, unsigned len);
 	int GetSampleRate() const { return SampleRate; }
+	float GetOffsetFix() const { return OffsetFix; }
+
 	RageSoundReader_MP3();
 	~RageSoundReader_MP3();
 	RageSoundReader_MP3( const RageSoundReader_MP3 & ); /* not defined; don't use */

stepmania/src/RageSoundReader_Preload.cpp

@@ -17,6 +17,7 @@ bool SoundReader_Preload::Open(SoundReader *source)
 {
 	ASSERT(source);
 	samplerate = source->GetSampleRate();
+	OffsetFix = source->GetOffsetFix(); // propagate upwards
 
 	/* Check the length, and see if we think it'll fit in the buffer. */
 	int len = source->GetLength_Fast();

stepmania/src/RageSoundReader_Preload.h

@@ -30,6 +30,7 @@ class SoundReader_Preload: public SoundReader {
 	int total_samples() const;
 
 	int samplerate;
+	float OffsetFix;
 
 public:
 	/* Return true if the sound has been preloaded, in which case source will
@@ -41,6 +42,7 @@ public:
 	int SetPosition_Fast(int ms);
 	int Read(char *buf, unsigned len);
 	int GetSampleRate() const { return samplerate; }
+	float GetOffsetFix() const { return OffsetFix; }
 
 	SoundReader *Copy() const;
 	~SoundReader_Preload() { }

stepmania/src/RageSoundReader_Resample_Fast.h

@@ -27,6 +27,7 @@ public:
 	RageSoundReader_Resample_Fast();
 	virtual ~RageSoundReader_Resample_Fast();
 	SoundReader *Copy() const;
+	float GetOffsetFix() const { return source->GetOffsetFix(); }
 
 	/* Change the actual sample rate of a sound. */
 	void SetSampleRate(int hz);

stepmania/src/RageSoundReader_Resample_Good.h

@@ -35,6 +35,7 @@ public:
 	RageSoundReader_Resample_Good();
 	virtual ~RageSoundReader_Resample_Good();
 	SoundReader *Copy() const;
+	float GetOffsetFix() const { return source->GetOffsetFix(); }
 
 	/* Change the actual sample rate of a sound. */
 	void SetSampleRate( int hz );