Initial community commit

Src/external_dependencies/openmpt-trunk/soundlib/SampleFormatBRR.cpp

@@ -0,0 +1,134 @@
+/*
+ * SampleFormatBRR.cpp
+ * -------------------
+ * Purpose: BRR (SNES Bit Rate Reduction) sample format import.
+ * Notes  : This format has no magic bytes, so frame headers are thoroughly validated.
+ * Authors: OpenMPT Devs
+ * The OpenMPT source code is released under the BSD license. Read LICENSE for more details.
+ */
+
+
+#include "stdafx.h"
+#include "Sndfile.h"
+#include "../common/FileReader.h"
+
+
+OPENMPT_NAMESPACE_BEGIN
+
+
+static void ProcessBRRSample(int32 sample, int16 *output, uint8 range, uint8 filter)
+{
+	if(sample >= 8)
+		sample -= 16;
+
+	if(range <= 12)
+		sample = mpt::rshift_signed(mpt::lshift_signed(sample, range), 1);
+	else
+		sample = (sample < 0) ? -2048 : 0;  // Implementations do not fully agree on what to do in this case. This is what bsnes does.
+
+	// Apply prediction filter
+	// Note 1: It is okay that we may access data before the first sample point because this memory is reserved for interpolation
+	// Note 2: The use of signed shift arithmetic is crucial for some samples (e.g. killer lead.brr, Mac2.brr)
+	// Note 3: Divisors are twice of what is written in the respective comments, as all sample data is divided by 2 (again crucial for accuracy)
+	static_assert(InterpolationLookaheadBufferSize >= 2);
+	switch(filter)
+	{
+	case 1:  // y(n) = x(n) + x(n-1) * 15/16
+		sample += mpt::rshift_signed(output[-1] * 15, 5);
+		break;
+	case 2:  // y(n) = x(n) + x(n-1) * 61/32 - x(n-2) * 15/16
+		sample += mpt::rshift_signed(output[-1] * 61, 6) + mpt::rshift_signed(output[-2] * -15, 5);
+		break;
+	case 3:  // y(n) = x(n) + x(n-1) * 115/64 - x(n-2) * 13/16
+		sample += mpt::rshift_signed(output[-1] * 115, 7) + mpt::rshift_signed(output[-2] * -13, 5);
+		break;
+	}
+
+	sample = std::clamp(sample, int32(-32768), int32(32767)) * 2;
+	if(sample > 32767)
+		sample -= 65536;
+	else if(sample < -32768)
+		sample += 65536;
+	output[0] = static_cast<int16>(sample);
+}
+
+
+bool CSoundFile::ReadBRRSample(SAMPLEINDEX sample, FileReader &file)
+{
+	const auto fileSize = file.GetLength();
+	if(fileSize < 9 || fileSize > uint16_max)
+		return false;
+	const bool hasLoopInfo = (fileSize % 9) == 2;
+	if((fileSize % 9) != 0 && !hasLoopInfo)
+		return false;
+	
+	file.Rewind();
+
+	SmpLength loopStart = 0;
+	if(hasLoopInfo)
+	{
+		loopStart = file.ReadUint16LE();
+		if(loopStart >= fileSize)
+			return false;
+		if((loopStart % 9) != 0)
+			return false;
+	}
+
+	// First scan the file for validity and consistency
+	// Note: There are some files with loop start set but ultimately the loop is never enabled. Cannot use this as a consistency check.
+	// Very few files also have a filter set on the first block, so we cannot reject those either.
+	bool enableLoop = false, first = true;
+	while(!file.EndOfFile())
+	{
+		const auto block = file.ReadArray<uint8, 9>();
+		const bool isLast = (block[0] & 0x01) != 0;
+		const bool isLoop = (block[0] & 0x02) != 0;
+		const uint8 range = block[0] >> 4u;
+		if(isLast != file.EndOfFile())
+			return false;
+		if(!first && enableLoop != isLoop)
+			return false;
+		// While a range of 13 is technically invalid as well, it can be found in the wild.
+		if(range > 13)
+			return false;
+		enableLoop = isLoop;
+		first = false;
+	}
+
+	file.Seek(hasLoopInfo ? 2 : 0);
+
+	DestroySampleThreadsafe(sample);
+	ModSample &mptSmp = Samples[sample];
+	mptSmp.Initialize();
+	mptSmp.uFlags = CHN_16BIT;
+	mptSmp.nLength = mpt::saturate_cast<SmpLength>((fileSize - (hasLoopInfo ? 2 : 0)) * 16 / 9);
+	if(enableLoop)
+		mptSmp.SetLoop(loopStart * 16 / 9, mptSmp.nLength, true, false, *this);
+	mptSmp.nC5Speed = 32000;
+	m_szNames[sample] = "";
+
+	if(!mptSmp.AllocateSample())
+		return false;
+
+	int16 *output = mptSmp.sample16();
+	while(!file.EndOfFile())
+	{
+		const auto block = file.ReadArray<uint8, 9>();
+		const uint8 range = block[0] >> 4u;
+		const uint8 filter = (block[0] >> 2) & 0x03;
+
+		for(int i = 0; i < 8; i++)
+		{
+			ProcessBRRSample(block[i + 1] >> 4u, output, range, filter);
+			ProcessBRRSample(block[i + 1] & 0x0F, output + 1, range, filter);
+			output += 2;
+		}
+	}
+	mptSmp.Convert(MOD_TYPE_IT, GetType());
+	mptSmp.PrecomputeLoops(*this, false);
+
+	return true;
+}
+
+
+OPENMPT_NAMESPACE_END