From 2b6ebf99559196491da9df06bf90b09665d218db Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <mclaughc@outlook.com>
Date: Tue, 15 Oct 2019 17:24:11 +1000
Subject: [PATCH] Common: Add helper functions for decoding CD-XA ADPCM

---
 src/common/cd_image.h             | 30 +---------
 src/common/cd_xa.cpp              | 98 +++++++++++++++++++++++++++++++
 src/common/cd_xa.h                | 70 ++++++++++++++++++++++
 src/common/common.vcxproj         |  2 +
 src/common/common.vcxproj.filters |  2 +
 5 files changed, 173 insertions(+), 29 deletions(-)
 create mode 100644 src/common/cd_xa.cpp
 create mode 100644 src/common/cd_xa.h

diff --git a/src/common/cd_image.h b/src/common/cd_image.h
index 8b3f6e1a8..b8f9f57ac 100644
--- a/src/common/cd_image.h
+++ b/src/common/cd_image.h
@@ -16,10 +16,9 @@ public:
     DATA_SECTOR_SIZE = 2048,
     SECTOR_SYNC_SIZE = 12,
     SECTOR_HEADER_SIZE = 4,
-    SECTOR_XA_SUBHEADER_SIZE = 4,
     FRAMES_PER_SECOND = 75, // "sectors"
     SECONDS_PER_MINUTE = 60,
-    FRAMES_PER_MINUTE = FRAMES_PER_SECOND * SECONDS_PER_MINUTE,
+    FRAMES_PER_MINUTE = FRAMES_PER_SECOND * SECONDS_PER_MINUTE
   };
 
   enum class ReadMode : u32
@@ -37,33 +36,6 @@ public:
     u8 sector_mode;
   };
 
-  struct XASubHeader
-  {
-    u8 file_number;
-    u8 channel_number;
-    union Submode
-    {
-      u8 bits;
-      BitField<u8, bool, 0, 1> eor;
-      BitField<u8, bool, 1, 1> video;
-      BitField<u8, bool, 2, 1> audio;
-      BitField<u8, bool, 3, 1> data;
-      BitField<u8, bool, 4, 1> trigger;
-      BitField<u8, bool, 5, 1> form2;
-      BitField<u8, bool, 6, 1> realtime;
-      BitField<u8, bool, 7, 1> eof;
-    } submode;
-    union Codinginfo
-    {
-      u8 bits;
-
-      BitField<u8, u8, 0, 2> mono_stereo;
-      BitField<u8, u8, 2, 2> sample_rate;
-      BitField<u8, u8, 4, 2> bits_per_sample;
-      BitField<u8, bool, 6, 1> emphasis;
-    } codinginfo;
-  };
-
   // Conversion helpers.
   static constexpr u64 MSFToLBA(u32 pregap_seconds, u32 minute, u32 second, u32 frame);
   static constexpr void LBAToMSF(u32 pregap_seconds, u64 lba, u32* minute, u32* second, u32* frame);
diff --git a/src/common/cd_xa.cpp b/src/common/cd_xa.cpp
new file mode 100644
index 000000000..4c5ec82ea
--- /dev/null
+++ b/src/common/cd_xa.cpp
@@ -0,0 +1,98 @@
+#include "cd_xa.h"
+#include "cd_image.h"
+#include <algorithm>
+#include <array>
+
+namespace CDXA {
+static constexpr std::array<s32, 4> s_xa_adpcm_filter_table_pos = {{0, 60, 115, 98}};
+static constexpr std::array<s32, 4> s_xa_adpcm_filter_table_neg = {{0, 0, -52, -55}};
+
+template<bool IS_STEREO, bool IS_8BIT>
+static void DecodeXA_ADPCMChunk(const u8* chunk_ptr, s16* samples, s32* last_samples)
+{
+  // The data layout is annoying here. Each word of data is interleaved with the other blocks, requiring multiple
+  // passes to decode the whole chunk.
+  constexpr u32 NUM_BLOCKS = IS_8BIT ? 4 : 8;
+  constexpr u32 WORDS_PER_BLOCK = 28;
+
+  const u8* headers_ptr = chunk_ptr + 4;
+  const u8* words_ptr = chunk_ptr + 16;
+
+  for (u32 block = 0; block < NUM_BLOCKS; block++)
+  {
+    const XA_ADPCMBlockHeader block_header{headers_ptr[block]};
+    const u8 shift = block_header.GetShift();
+    const u8 filter = block_header.GetFilter();
+    const s32 filter_pos = s_xa_adpcm_filter_table_pos[filter];
+    const s32 filter_neg = s_xa_adpcm_filter_table_neg[filter];
+
+    s16* out_samples_ptr =
+      IS_STEREO ? &samples[(block / 2) * (WORDS_PER_BLOCK * 2) + (block % 2)] : &samples[block * WORDS_PER_BLOCK];
+    constexpr u32 out_samples_increment = IS_STEREO ? 2 : 1;
+
+    for (u32 word = 0; word < 28; word++)
+    {
+      // NOTE: assumes LE
+      u32 word_data;
+      std::memcpy(&word_data, &words_ptr[word * sizeof(u32)], sizeof(word_data));
+
+      // extract nibble from block
+      const u32 nibble = IS_8BIT ? ((word_data >> (block * 8)) & 0xFF) : ((word_data >> (block * 4)) & 0x0F);
+      const s16 sample = static_cast<s16>(Truncate16(nibble << 12)) >> shift;
+
+      // mix in previous values
+      s32* prev = IS_STEREO ? &last_samples[(block & 1) * 2] : last_samples;
+      const s32 interp_sample = s32(sample) + ((prev[0] * filter_pos) + (prev[1] * filter_neg) + 32) / 64;
+
+      // update previous values
+      prev[1] = prev[0];
+      prev[0] = interp_sample;
+
+      *out_samples_ptr = static_cast<s16>(std::clamp<s32>(interp_sample, -0x8000, 0x7FFF));
+      out_samples_ptr += out_samples_increment;
+    }
+  }
+}
+
+template<bool IS_STEREO, bool IS_8BIT>
+static void DecodeXA_ADPCMChunks(const u8* chunk_ptr, s16* samples, s32* last_samples)
+{
+  constexpr u32 NUM_CHUNKS = 18;
+  constexpr u32 CHUNK_SIZE_IN_BYTES = 128;
+  constexpr u32 WORDS_PER_CHUNK = 28;
+  constexpr u32 SAMPLES_PER_CHUNK = 28 * (IS_8BIT ? 4 : 8);
+
+  for (u32 i = 0; i < NUM_CHUNKS; i++)
+  {
+    DecodeXA_ADPCMChunk<IS_STEREO, IS_8BIT>(chunk_ptr, samples, last_samples);
+    samples += SAMPLES_PER_CHUNK;
+    chunk_ptr += CHUNK_SIZE_IN_BYTES;
+  }
+}
+
+void DecodeADPCMSector(const void* data, s16* samples, s32* last_samples)
+{
+  const XASubHeader* subheader = reinterpret_cast<const XASubHeader*>(
+    reinterpret_cast<const u8*>(data) + CDImage::SECTOR_SYNC_SIZE + sizeof(CDImage::SectorHeader));
+
+  // The XA subheader is repeated?
+  const u8* chunk_ptr = reinterpret_cast<const u8*>(data) + CDImage::SECTOR_SYNC_SIZE + sizeof(CDImage::SectorHeader) +
+                        sizeof(XASubHeader) + 4;
+
+  if (subheader->codinginfo.bits_per_sample != 1)
+  {
+    if (subheader->codinginfo.mono_stereo != 1)
+      DecodeXA_ADPCMChunks<false, false>(chunk_ptr, samples, last_samples);
+    else
+      DecodeXA_ADPCMChunks<true, false>(chunk_ptr, samples, last_samples);
+  }
+  else
+  {
+    if (subheader->codinginfo.mono_stereo != 1)
+      DecodeXA_ADPCMChunks<false, true>(chunk_ptr, samples, last_samples);
+    else
+      DecodeXA_ADPCMChunks<true, true>(chunk_ptr, samples, last_samples);
+  }
+}
+
+} // namespace CDXA
diff --git a/src/common/cd_xa.h b/src/common/cd_xa.h
new file mode 100644
index 000000000..3e996d16c
--- /dev/null
+++ b/src/common/cd_xa.h
@@ -0,0 +1,70 @@
+#pragma once
+#include "bitfield.h"
+#include "types.h"
+
+namespace CDXA {
+enum
+{
+  XA_SUBHEADER_SIZE = 4,
+  XA_ADPCM_SAMPLES_PER_SECTOR_4BIT = 4032, // 28 words * 8 nibbles per word * 18 chunks
+  XA_ADPCM_SAMPLES_PER_SECTOR_8BIT = 2016  // 28 words * 4 bytes per word * 18 chunks
+};
+
+struct XASubHeader
+{
+  u8 file_number;
+  u8 channel_number;
+  union Submode
+  {
+    u8 bits;
+    BitField<u8, bool, 0, 1> eor;
+    BitField<u8, bool, 1, 1> video;
+    BitField<u8, bool, 2, 1> audio;
+    BitField<u8, bool, 3, 1> data;
+    BitField<u8, bool, 4, 1> trigger;
+    BitField<u8, bool, 5, 1> form2;
+    BitField<u8, bool, 6, 1> realtime;
+    BitField<u8, bool, 7, 1> eof;
+  } submode;
+  union Codinginfo
+  {
+    u8 bits;
+
+    BitField<u8, u8, 0, 2> mono_stereo;
+    BitField<u8, u8, 2, 2> sample_rate;
+    BitField<u8, u8, 4, 2> bits_per_sample;
+    BitField<u8, bool, 6, 1> emphasis;
+
+    bool IsStereo() const { return mono_stereo == 1; }
+    bool IsHalfSampleRate() const { return sample_rate == 1; }
+    u32 GetSampleRate() const { return sample_rate == 1 ? 18900 : 37800; }
+    u32 GetBitsPerSample() const { return bits_per_sample == 1 ? 8 : 4; }
+    u32 GetSamplesPerSector() const
+    {
+      return bits_per_sample == 1 ? XA_ADPCM_SAMPLES_PER_SECTOR_8BIT : XA_ADPCM_SAMPLES_PER_SECTOR_4BIT;
+    }
+  } codinginfo;
+};
+
+union XA_ADPCMBlockHeader
+{
+  u8 bits;
+
+  BitField<u8, u8, 0, 4> shift;
+  BitField<u8, u8, 4, 2> filter;
+
+  // For both 4bit and 8bit ADPCM, reserved shift values 13..15 will act same as shift=9).
+  u8 GetShift() const
+  {
+    const u8 shift_value = shift;
+    return (shift_value > 12) ? 9 : shift_value;
+  }
+
+  u8 GetFilter() const { return filter; }
+};
+static_assert(sizeof(XA_ADPCMBlockHeader) == 1, "XA-ADPCM block header is one byte");
+
+// Decodes XA-ADPCM samples in an audio sector. Stereo samples are interleaved with left first.
+void DecodeADPCMSector(const void* data, s16* samples, s32* last_samples);
+
+} // namespace CDXA
\ No newline at end of file
diff --git a/src/common/common.vcxproj b/src/common/common.vcxproj
index 2a2e9f5da..7dfcf0ec5 100644
--- a/src/common/common.vcxproj
+++ b/src/common/common.vcxproj
@@ -56,6 +56,7 @@
     <ClInclude Include="state_wrapper.h" />
     <ClInclude Include="types.h" />
     <ClInclude Include="type_registry.h" />
+    <ClInclude Include="cd_xa.h" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="audio.cpp" />
@@ -74,6 +75,7 @@
     <ClCompile Include="object_type_info.cpp" />
     <ClCompile Include="property.cpp" />
     <ClCompile Include="state_wrapper.cpp" />
+    <ClCompile Include="cd_xa.cpp" />
   </ItemGroup>
   <ItemGroup>
     <Natvis Include="bitfield.natvis" />
diff --git a/src/common/common.vcxproj.filters b/src/common/common.vcxproj.filters
index d98ca1c1a..063903cf6 100644
--- a/src/common/common.vcxproj.filters
+++ b/src/common/common.vcxproj.filters
@@ -22,6 +22,7 @@
     <ClInclude Include="fifo_queue.h" />
     <ClInclude Include="cd_image.h" />
     <ClInclude Include="audio_stream.h" />
+    <ClInclude Include="cd_xa.h" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="hdd_image.cpp" />
@@ -40,6 +41,7 @@
     <ClCompile Include="gl_texture.cpp" />
     <ClCompile Include="cd_image.cpp" />
     <ClCompile Include="audio_stream.cpp" />
+    <ClCompile Include="cd_xa.cpp" />
   </ItemGroup>
   <ItemGroup>
     <Natvis Include="bitfield.natvis" />