basis_universal: Update to upstream commit from Apr 16, 2021

BinomialLLC/basis_universal@ba1c3e40f1.

thirdparty/basis_universal/transcoder/basisu_file_headers.h

@@ -1,5 +1,5 @@
 // basis_file_headers.h
-// Copyright (C) 2019 Binomial LLC. All Rights Reserved.
+// Copyright (C) 2019-2020 Binomial LLC. All Rights Reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -20,8 +20,11 @@ namespace basist
 	// Slice desc header flags
 	enum basis_slice_desc_flags
 	{
-		cSliceDescFlagsIsAlphaData = 1,
-		cSliceDescFlagsFrameIsIFrame = 2			// Video only: Frame doesn't refer to previous frame (no usage of conditional replenishment pred symbols)
+		cSliceDescFlagsHasAlpha = 1,
+		
+		// Video only: Frame doesn't refer to previous frame (no usage of conditional replenishment pred symbols)
+		// Currently the first frame is always an I-Frame, all subsequent frames are P-Frames. This will eventually be changed to periodic I-Frames.
+		cSliceDescFlagsFrameIsIFrame = 2			
 	};
 
 #pragma pack(push)
@@ -38,7 +41,7 @@ namespace basist
 		basisu::packed_uint<2> m_num_blocks_x;	// The slice's block X dimensions. Each block is 4x4 pixels. The slice's pixel resolution may or may not be a power of 2.
 		basisu::packed_uint<2> m_num_blocks_y;	// The slice's block Y dimensions. 
 
-		basisu::packed_uint<4> m_file_ofs;		// Offset from the header to the start of the slice's data
+		basisu::packed_uint<4> m_file_ofs;		// Offset from the start of the file to the start of the slice's data
 		basisu::packed_uint<4> m_file_size;		// The size of the compressed slice data in bytes
 
 		basisu::packed_uint<2> m_slice_data_crc16; // The CRC16 of the compressed slice data, for extra-paranoid use cases
@@ -47,9 +50,21 @@ namespace basist
 	// File header files
 	enum basis_header_flags
 	{
-		cBASISHeaderFlagETC1S = 1,					// Always set for basis universal files
-		cBASISHeaderFlagYFlipped = 2,				// Set if the texture had to be Y flipped before encoding
-		cBASISHeaderFlagHasAlphaSlices = 4		// True if the odd slices contain alpha data
+		// Always set for ETC1S files. Not set for UASTC files.
+		cBASISHeaderFlagETC1S = 1,					 
+		
+		// Set if the texture had to be Y flipped before encoding. The actual interpretation of this (is Y up or down?) is up to the user.
+		cBASISHeaderFlagYFlipped = 2,				 
+		
+		// Set if any slices contain alpha (for ETC1S, if the odd slices contain alpha data)
+		cBASISHeaderFlagHasAlphaSlices = 4,		 
+		
+		// For ETC1S files, this will be true if the file utilizes a codebook from another .basis file. 
+		cBASISHeaderFlagUsesGlobalCodebook = 8, 
+		
+		// Set if the texture data is sRGB, otherwise it's linear. 
+		// In reality, we have no idea if the texture data is actually linear or sRGB. This is the m_perceptual parameter passed to the compressor.
+		cBASISHeaderFlagSRGB = 16,					 
 	};
 
 	// The image type field attempts to describe how to interpret the image data in a Basis file.
@@ -71,6 +86,12 @@ namespace basist
 		cBASISMaxUSPerFrame = 0xFFFFFF
 	};
 
+	enum class basis_tex_format
+	{
+		cETC1S = 0,
+		cUASTC4x4 = 1
+	};
+
 	struct basis_file_header
 	{
 		enum
@@ -82,16 +103,16 @@ namespace basist
 		basisu::packed_uint<2>      m_sig;				// 2 byte file signature
 		basisu::packed_uint<2>      m_ver;				// Baseline file version
 		basisu::packed_uint<2>      m_header_size;	// Header size in bytes, sizeof(basis_file_header)
-		basisu::packed_uint<2>      m_header_crc16;	// crc16 of the remaining header data
+		basisu::packed_uint<2>      m_header_crc16;	// CRC16 of the remaining header data
 
 		basisu::packed_uint<4>      m_data_size;		// The total size of all data after the header
 		basisu::packed_uint<2>      m_data_crc16;		// The CRC16 of all data after the header
 
-		basisu::packed_uint<3>      m_total_slices;	// The total # of compressed slices (1 slice per image, or 2 for alpha basis files)
+		basisu::packed_uint<3>      m_total_slices;	// The total # of compressed slices (1 slice per image, or 2 for alpha .basis files)
 
 		basisu::packed_uint<3>      m_total_images;	// The total # of images
 				
-		basisu::packed_uint<1>      m_format;			// enum basist::block_format
+		basisu::packed_uint<1>      m_tex_format;		// enum basis_tex_format
 		basisu::packed_uint<2>      m_flags;			// enum basist::header_flags
 		basisu::packed_uint<1>      m_tex_type;		// enum basist::basis_texture_type
 		basisu::packed_uint<3>      m_us_per_frame;	// Framerate of video, in microseconds per frame
@@ -101,11 +122,11 @@ namespace basist
 		basisu::packed_uint<4>      m_userdata1;		// For client use
 
 		basisu::packed_uint<2>      m_total_endpoints;			// The number of endpoints in the endpoint codebook 
-		basisu::packed_uint<4>      m_endpoint_cb_file_ofs;	// The compressed endpoint codebook's file offset relative to the header
+		basisu::packed_uint<4>      m_endpoint_cb_file_ofs;	// The compressed endpoint codebook's file offset relative to the start of the file
 		basisu::packed_uint<3>      m_endpoint_cb_file_size;	// The compressed endpoint codebook's size in bytes
 
 		basisu::packed_uint<2>      m_total_selectors;			// The number of selectors in the endpoint codebook 
-		basisu::packed_uint<4>      m_selector_cb_file_ofs;	// The compressed selectors codebook's file offset relative to the header
+		basisu::packed_uint<4>      m_selector_cb_file_ofs;	// The compressed selectors codebook's file offset relative to the start of the file
 		basisu::packed_uint<3>      m_selector_cb_file_size;	// The compressed selector codebook's size in bytes
 
 		basisu::packed_uint<4>      m_tables_file_ofs;			// The file offset of the compressed Huffman codelength tables, for decompressing slices