/***************************************************************************
*
* Copyright (c) Microsoft Corporation. All rights reserved.
*
* File: xma2defs.h
* Content: Constants, data types and functions for XMA2 compressed audio.
*
***************************************************************************/
#ifndef __XMA2DEFS_INCLUDED__
#define __XMA2DEFS_INCLUDED__
#include <sal.h> // Markers for documenting API semantics
#include <winerror.h> // For S_OK, E_FAIL
#include <audiodefs.h> // Basic data types and constants for audio work
/***************************************************************************
* Overview
***************************************************************************/
// A typical XMA2 file contains these RIFF chunks:
//
// 'fmt' or 'XMA2' chunk (or both): A description of the XMA data's structure
// and characteristics (length, channels, sample rate, loops, block size, etc).
//
// 'seek' chunk: A seek table to help navigate the XMA data.
//
// 'data' chunk: The encoded XMA2 data.
//
// The encoded XMA2 data is structured as a set of BLOCKS, which contain PACKETS,
// which contain FRAMES, which contain SUBFRAMES (roughly speaking). The frames
// in a file may also be divided into several subsets, called STREAMS.
//
// FRAME: A variable-sized segment of XMA data that decodes to exactly 512 mono
// or stereo PCM samples. This is the smallest unit of XMA data that can
// be decoded in isolation. Frames are an arbitrary number of bits in
// length, and need not be byte-aligned. See "XMA frame structure" below.
//
// SUBFRAME: A region of bits in an XMA frame that decodes to 128 mono or stereo
// samples. The XMA decoder cannot decode a subframe in isolation; it needs
// a whole frame to work with. However, it can begin emitting the frame's
// decoded samples at any one of the four subframe boundaries. Subframes
// can be addressed for seeking and looping purposes.
//
// PACKET: A 2Kb region containing a 32-bit header and some XMA frames. Frames
// can (and usually do) span packets. A packet's header includes the offset
// in bits of the first frame that begins within that packet. All of the
// frames that begin in a given packet belong to the same "stream" (see the
// Multichannel Audio section below).
//
// STREAM: A set of packets within an XMA file that all contain data for the
// same mono or stereo component of a PCM file with more than two channels.
// The packets comprising a given stream may be interleaved with each other
// more or less arbitrarily; see Multichannel Audio.
//
// BLOCK: An array of XMA packets; or, to break it down differently, a series of
// consecutive XMA frames, padded at the end with reserved data. A block
// must contain at least one 2Kb packet per stream, and it can hold up to
// 4095 packets (8190Kb), but its size is typically in the 32Kb-128Kb range.
// (The size chosen involves a trade-off between memory use and efficiency
// of reading from permanent storage.)
//
// XMA frames do not span blocks, so a block is guaranteed to begin with a
// set of complete frames, one per stream. Also, a block in a multi-stream
// XMA2 file always contains the same number of samples for each stream;
// see Multichannel Audio.
//
// The 'data' chunk in an XMA2 file is an array of XMA2WAVEFORMAT.BlockCount XMA
// blocks, all the same size (as specified in XMA2WAVEFORMAT.BlockSizeInBytes)
// except for the last one, which may be shorter.
// MULTICHANNEL AUDIO: the XMA decoder can only decode raw XMA data into either
// mono or stereo PCM data. In order to encode a 6-channel file (say), the file
// must be deinterleaved into 3 stereo streams that are encoded independently,
// producing 3 encoded XMA data streams. Then the packets in these 3 streams
// are interleaved to produce a single XMA2 file, and some information is added
// to the file so that the original 6-channel audio can be reconstructed at
// decode time. This works using the concept of an XMA stream (see above).
//
// The frames for all the streams in an XMA file are interleaved in an arbitrary
// order. To locate a frame that belongs to a given stream in a given XMA block,
// you must examine the first few packets in the block. Here (and only here) the
// packets are guaranteed to be presented in stream order, so that all frames
// beginning in packet 0 belong to stream 0 (the first stereo pair), etc.
//
// (This means that when decoding multi-stream XMA files, only entire XMA blocks
// should be submitted to the decoder; otherwise it cannot know which frames
// belong to which stream.)
//
// Once you have one frame that belongs to a given stream, you can find the next
// one by looking at the frame's 'NextFrameOffsetBits' value (which is stored in
// its first 15 bits; see XMAFRAME below). The GetXmaFrameBitPosition function
// uses this technique.
// SEEKING IN XMA2 FILES: Here is some pseudocode to find the byte position and
// subframe in an XMA2 file which will contain sample S when decoded.
//
// 1. Traverse the seek table to find the XMA2 block containing sample S. The
// seek table is an array of big-endian DWORDs, one per block in the file.
// The Nth DWORD is the total number of PCM samples that would be obtained
// by decoding the entire XMA file up to the end of block N. Hence, the
// block we want is the first one whose seek table entry is greater than S.
// (See the GetXmaBlockContainingSample helper function.)
//
// 2. Calculate which frame F within the block found above contains sample S.
// Since each frame decodes to 512 samples, this is straightforward. The
// first frame in the block produces samples X to X + 512, where X is the
// seek table entry for the prior block. So F is (S - X) / 512.
//
// 3. Find the bit offset within the block where frame F starts. Since frames
// are variable-sized, this can only be done by traversing all the frames in
// the block until we reach frame F. (See GetXmaFrameBitPosition.)
//
// 4. Frame F has four 128-sample subframes. To find the subframe containing S,
// we can use the formula (S % 512) / 128.
//
// In the case of multi-stream XMA files, sample S is a multichannel sample with
// parts coming from several frames, one per stream. To find all these frames,
// steps 2-4 need to be repeated for each stream N, using the knowledge that the
// first packets in a block are presented in stream order. The frame traversal
// in step 3 must be started at the first frame in the Nth packet of the block,
// which will be the first frame for stream N. (And the packet header will tell
// you the first frame's start position within the packet.)
//
// Step 1 can be performed using the GetXmaBlockContainingSample function below,
// and steps 2-4 by calling GetXmaDecodePositionForSample once for each stream.
/***************************************************************************
* XMA constants
***************************************************************************/
// Size of the PCM samples produced by the XMA decoder
#define XMA_OUTPUT_SAMPLE_BYTES 2u
#define XMA_OUTPUT_SAMPLE_BITS (XMA_OUTPUT_SAMPLE_BYTES * 8u)
// Size of an XMA packet
#define XMA_BYTES_PER_PACKET 2048u
#define XMA_BITS_PER_PACKET (XMA_BYTES_PER_PACKET * 8u)
// Size of an XMA packet header
#define XMA_PACKET_HEADER_BYTES 4u
#define XMA_PACKET_HEADER_BITS (XMA_PACKET_HEADER_BYTES * 8u)
// Sample blocks in a decoded XMA frame
#define XMA_SAMPLES_PER_FRAME 512u
// Sample blocks in a decoded XMA subframe
#define XMA_SAMPLES_PER_SUBFRAME 128u
// Maximum encoded data that can be submitted to the XMA decoder at a time
#define XMA_READBUFFER_MAX_PACKETS 4095u
#define XMA_READBUFFER_MAX_BYTES (XMA_READBUFFER_MAX_PACKETS * XMA_BYTES_PER_PACKET)
// Maximum size allowed for the XMA decoder's output buffers
#define XMA_WRITEBUFFER_MAX_BYTES (31u * 256u)
// Required byte alignment of the XMA decoder's output buffers
#define XMA_WRITEBUFFER_BYTE_ALIGNMENT 256u
// Decode chunk sizes for the XMA_PLAYBACK_INIT.subframesToDecode field
#define XMA_MIN_SUBFRAMES_TO_DECODE 1u
#define XMA_MAX_SUBFRAMES_TO_DECODE 8u
#define XMA_OPTIMAL_SUBFRAMES_TO_DECODE 4u
// LoopCount<255 means finite repetitions; LoopCount=255 means infinite looping
#define XMA_MAX_LOOPCOUNT 254u
#define XMA_INFINITE_LOOP 255u
/***************************************************************************
* XMA format structures
***************************************************************************/
// The currently recommended way to express format information for XMA2 files
// is the XMA2WAVEFORMATEX structure. This structure is fully compliant with
// the WAVEFORMATEX standard and contains all the information needed to parse
// and manage XMA2 files in a compact way.
#define WAVE_FORMAT_XMA2 0x166
typedef struct XMA2WAVEFORMATEX
{
WAVEFORMATEX wfx;
// Meaning of the WAVEFORMATEX fields here:
// wFormatTag; // Audio format type; always WAVE_FORMAT_XMA2
// nChannels; // Channel count of the decoded audio
// nSamplesPerSec; // Sample rate of the decoded audio
// nAvgBytesPerSec; // Used internally by the XMA encoder
// nBlockAlign; // Decoded sample size; channels * wBitsPerSample / 8
// wBitsPerSample; // Bits per decoded mono sample; always 16 for XMA
// cbSize; // Size in bytes of the rest of this structure (34)
WORD NumStreams; // Number of audio streams (1 or 2 channels each)
DWORD ChannelMask; // Spatial positions of the channels in this file,
// stored as SPEAKER_xxx values (see audiodefs.h)
DWORD SamplesEncoded; // Total number of PCM samples the file decodes to
DWORD BytesPerBlock; // XMA block size (but the last one may be shorter)
DWORD PlayBegin; // First valid sample in the decoded audio
DWORD PlayLength; // Length of the valid part of the decoded audio
DWORD LoopBegin; // Beginning of the loop region in decoded sample terms
DWORD LoopLength; // Length of the loop region in decoded sample terms
BYTE LoopCount; // Number of loop repetitions; 255 = infinite
BYTE EncoderVersion; // Version of XMA encoder that generated the file
WORD BlockCount; // XMA blocks in file (and entries in its seek table)
} XMA2WAVEFORMATEX, *PXMA2WAVEFORMATEX;
// The legacy XMA format structures are described here for reference, but they
// should not be used in new content. XMAWAVEFORMAT was the structure used in
// XMA version 1 files. XMA2WAVEFORMAT was used in early XMA2 files; it is not
// placed in the usual 'fmt' RIFF chunk but in its own 'XMA2' chunk.
#ifndef WAVE_FORMAT_XMA
#define WAVE_FORMAT_XMA 0x0165
// Values used in the ChannelMask fields below. Similar to the SPEAKER_xxx
// values defined in audiodefs.h, but modified to fit in a single byte.
#ifndef XMA_SPEAKER_LEFT
#define XMA_SPEAKER_LEFT 0x01
#define XMA_SPEAKER_RIGHT 0x02
#define XMA_SPEAKER_CENTER 0x04
#define XMA_SPEAKER_LFE 0x08
#define XMA_SPEAKER_LEFT_SURROUND 0x10
#define XMA_SPEAKER_RIGHT_SURROUND 0x20
#define XMA_SPEAKER_LEFT_BACK 0x40
#define XMA_SPEAKER_RIGHT_BACK 0x80
#endif
// Used in XMAWAVEFORMAT for per-stream data
typedef struct XMASTREAMFORMAT
{
DWORD PsuedoBytesPerSec; // Used by the XMA encoder (typo preserved for legacy reasons)
DWORD SampleRate; // The stream's decoded sample rate (in XMA2 files,
// this is the same for all streams in the file).
DWORD LoopStart; // Bit offset of the frame containing the loop start
// point, relative to the beginning of the stream.
DWORD LoopEnd; // Bit offset of the frame containing the loop end.
BYTE SubframeData; // Two 4-bit numbers specifying the exact location of
// the loop points within the frames that contain them.
// SubframeEnd: Subframe of the loop end frame where
// the loop ends. Ranges from 0 to 3.
// SubframeSkip: Subframes to skip in the start frame to
// reach the loop. Ranges from 0 to 4.
BYTE Channels; // Number of channels in the stream (1 or 2)
WORD ChannelMask; // Spatial positions of the channels in the stream
} XMASTREAMFORMAT;
// Legacy XMA1 format structure
typedef struct XMAWAVEFORMAT
{
WORD FormatTag; // Audio format type (always WAVE_FORMAT_XMA)
WORD BitsPerSample; // Bit depth (currently required to be 16)
WORD EncodeOptions; // Options for XMA encoder/decoder
WORD LargestSkip; // Largest skip used in interleaving streams
WORD NumStreams; // Number of interleaved audio streams
BYTE LoopCount; // Number of loop repetitions; 255 = infinite
BYTE Version; // XMA encoder version that generated the file.
// Always 3 or higher for XMA2 files.
XMASTREAMFORMAT XmaStreams[1]; // Per-stream format information; the actual
// array length is in the NumStreams field.
} XMAWAVEFORMAT;
// Used in XMA2WAVEFORMAT for per-stream data
typedef struct XMA2STREAMFORMAT
{
BYTE Channels; // Number of channels in the stream (1 or 2)
BYTE RESERVED; // Reserved for future use
WORD ChannelMask; // Spatial positions of the channels in the stream
} XMA2STREAMFORMAT;
// Legacy XMA2 format structure (big-endian byte ordering)
typedef struct XMA2WAVEFORMAT
{
BYTE Version; // XMA encoder version that generated the file.
// Always 3 or higher for XMA2 files.
BYTE NumStreams; // Number of interleaved audio streams
BYTE RESERVED; // Reserved for future use
BYTE LoopCount; // Number of loop repetitions; 255 = infinite
DWORD LoopBegin; // Loop begin point, in samples
DWORD LoopEnd; // Loop end point, in samples
DWORD SampleRate; // The file's decoded sample rate
DWORD EncodeOptions; // Options for the XMA encoder/decoder
DWORD PsuedoBytesPerSec; // Used internally by the XMA encoder
DWORD BlockSizeInBytes; // Size in bytes of this file's XMA blocks (except
// possibly the last one). Always a multiple of
// 2Kb, since XMA blocks are arrays of 2Kb packets.
DWORD SamplesEncoded; // Total number of PCM samples encoded in this file
DWORD SamplesInSource; // Actual number of PCM samples in the source
// material used to generate this file
DWORD BlockCount; // Number of XMA blocks in this file (and hence
// also the number of entries in its seek table)
XMA2STREAMFORMAT Streams[1]; // Per-stream format information; the actual
// array length is in the NumStreams field.
} XMA2WAVEFORMAT;
#endif // #ifndef WAVE_FORMAT_XMA
/***************************************************************************
* XMA packet structure (in big-endian form)
***************************************************************************/
typedef struct XMA2PACKET
{
int FrameCount : 6; // Number of XMA frames that begin in this packet
int FrameOffsetInBits : 15; // Bit of XmaData where the first complete frame begins
int PacketMetaData : 3; // Metadata stored in the packet (always 1 for XMA2)
int PacketSkipCount : 8; // How many packets belonging to other streams must be
// skipped to find the next packet belonging to this one
BYTE XmaData[XMA_BYTES_PER_PACKET - sizeof(DWORD)]; // XMA encoded data
} XMA2PACKET;
// E.g. if the first DWORD of a packet is 0x30107902:
//
// 001100 000001000001111 001 00000010
// | | | |____ Skip 2 packets to find the next one for this stream
// | | |___________ XMA2 signature (always 001)
// | |_____________________ First frame starts 527 bits into packet
// |________________________________ Packet contains 12 frames
// Helper functions to extract the fields above from an XMA packet. (Note that
// the bitfields cannot be read directly on little-endian architectures such as
// the Intel x86, as they are laid out in big-endian form.)
__inline DWORD GetXmaPacketFrameCount(__in_bcount(1) const BYTE* pPacket)
{
return (DWORD)(pPacket[0] >> 2);
}
__inline DWORD GetXmaPacketFirstFrameOffsetInBits(__in_bcount(3) const BYTE* pPacket)
{
return ((DWORD)(pPacket[0] & 0x3) << 13) |
((DWORD)(pPacket[1]) << 5) |
((DWORD)(pPacket[2]) >> 3);
}
__inline DWORD GetXmaPacketMetadata(__in_bcount(3) const BYTE* pPacket)
{
return (DWORD)(pPacket[2] & 0x7);
}
__inline DWORD GetXmaPacketSkipCount(__in_bcount(4) const BYTE* pPacket)
{
return (DWORD)(pPacket[3]);
}
/***************************************************************************
* XMA frame structure
***************************************************************************/
// There is no way to represent the XMA frame as a C struct, since it is a
// variable-sized string of bits that need not be stored at a byte-aligned
// position in memory. This is the layout:
//
// XMAFRAME
// {
// LengthInBits: A 15-bit number representing the length of this frame.
// XmaData: Encoded XMA data; its size in bits is (LengthInBits - 15).
// }
// Size in bits of the frame's initial LengthInBits field
#define XMA_BITS_IN_FRAME_LENGTH_FIELD 15
// Special LengthInBits value that marks an invalid final frame
#define XMA_FINAL_FRAME_MARKER 0x7FFF
/***************************************************************************
* XMA helper functions
***************************************************************************/
// We define a local ASSERT macro to equal the global one if it exists.
// You can define XMA2DEFS_ASSERT in advance to override this default.
#ifndef XMA2DEFS_ASSERT
#ifdef ASSERT
#define XMA2DEFS_ASSERT ASSERT
#else
#define XMA2DEFS_ASSERT(a) /* No-op by default */
#endif
#endif
// GetXmaBlockContainingSample: Use a given seek table to find the XMA block
// containing a given decoded sample. Note that the seek table entries in an
// XMA file are stored in big-endian form and may need to be converted prior
// to calling this function.
__inline HRESULT GetXmaBlockContainingSample
(
DWORD nBlockCount, // Blocks in the file (= seek table entries)
__in_ecount(nBlockCount) const DWORD* pSeekTable, // Pointer to the seek table data
DWORD nDesiredSample, // Decoded sample to locate
__out DWORD* pnBlockContainingSample, // Index of the block containing the sample
__out DWORD* pnSampleOffsetWithinBlock // Position of the sample in this block
)
{
DWORD nPreviousTotalSamples = 0;
DWORD nBlock;
DWORD nTotalSamplesSoFar;
XMA2DEFS_ASSERT(pSeekTable);
XMA2DEFS_ASSERT(pnBlockContainingSample);
XMA2DEFS_ASSERT(pnSampleOffsetWithinBlock);
for (nBlock = 0; nBlock < nBlockCount; ++nBlock)
{
nTotalSamplesSoFar = pSeekTable[nBlock];
if (nTotalSamplesSoFar > nDesiredSample)
{
*pnBlockContainingSample = nBlock;
*pnSampleOffsetWithinBlock = nDesiredSample - nPreviousTotalSamples;
return S_OK;
}
nPreviousTotalSamples = nTotalSamplesSoFar;
}
return E_FAIL;
}
// GetXmaFrameLengthInBits: Reads a given frame's LengthInBits field.
__inline DWORD GetXmaFrameLengthInBits
(
__in_bcount(nBitPosition / 8 + 3)
__in const BYTE* pPacket, // Pointer to XMA packet[s] containing the frame
DWORD nBitPosition // Bit offset of the frame within this packet
)
{
DWORD nRegion;
DWORD nBytePosition = nBitPosition / 8;
DWORD nBitOffset = nBitPosition % 8;
if (nBitOffset < 2) // Only need to read 2 bytes (and might not be safe to read more)
{
nRegion = (DWORD)(pPacket[nBytePosition+0]) << 8 |
(DWORD)(pPacket[nBytePosition+1]);
return (nRegion >> (1 - nBitOffset)) & 0x7FFF; // Last 15 bits
}
else // Need to read 3 bytes
{
nRegion = (DWORD)(pPacket[nBytePosition+0]) << 16 |
(DWORD)(pPacket[nBytePosition+1]) << 8 |
(DWORD)(pPacket[nBytePosition+2]);
return (nRegion >> (9 - nBitOffset)) & 0x7FFF; // Last 15 bits
}
}
// GetXmaFrameBitPosition: Calculates the bit offset of a given frame within
// an XMA block or set of blocks. Returns 0 on failure.
__inline DWORD GetXmaFrameBitPosition
(
__in_bcount(nXmaDataBytes) const BYTE* pXmaData, // Pointer to XMA block[s]
DWORD nXmaDataBytes, // Size of pXmaData in bytes
DWORD nStreamIndex, // Stream within which to seek
DWORD nDesiredFrame // Frame sought
)
{
const BYTE* pCurrentPacket;
DWORD nPacketsExamined = 0;
DWORD nFrameCountSoFar = 0;
DWORD nFramesToSkip;
DWORD nFrameBitOffset;
XMA2DEFS_ASSERT(pXmaData);
XMA2DEFS_ASSERT(nXmaDataBytes % XMA_BYTES_PER_PACKET == 0);
// Get the first XMA packet belonging to the desired stream, relying on the
// fact that the first packets for each stream are in consecutive order at
// the beginning of an XMA block.
pCurrentPacket = pXmaData + nStreamIndex * XMA_BYTES_PER_PACKET;
for (;;)
{
// If we have exceeded the size of the XMA data, return failure
if (pCurrentPacket + XMA_BYTES_PER_PACKET > pXmaData + nXmaDataBytes)
{
return 0;
}
// If the current packet contains the frame we are looking for...
if (nFrameCountSoFar + GetXmaPacketFrameCount(pCurrentPacket) > nDesiredFrame)
{
// See how many frames in this packet we need to skip to get to it
XMA2DEFS_ASSERT(nDesiredFrame >= nFrameCountSoFar);
nFramesToSkip = nDesiredFrame - nFrameCountSoFar;
// Get the bit offset of the first frame in this packet
nFrameBitOffset = XMA_PACKET_HEADER_BITS + GetXmaPacketFirstFrameOffsetInBits(pCurrentPacket);
// Advance nFrameBitOffset to the frame of interest
while (nFramesToSkip--)
{
nFrameBitOffset += GetXmaFrameLengthInBits(pCurrentPacket, nFrameBitOffset);
}
// The bit offset to return is the number of bits from pXmaData to
// pCurrentPacket plus the bit offset of the frame of interest
return (DWORD)(pCurrentPacket - pXmaData) * 8 + nFrameBitOffset;
}
// If we haven't found the right packet yet, advance our counters
++nPacketsExamined;
nFrameCountSoFar += GetXmaPacketFrameCount(pCurrentPacket);
// And skip to the next packet belonging to the same stream
pCurrentPacket += XMA_BYTES_PER_PACKET * (GetXmaPacketSkipCount(pCurrentPacket) + 1);
}
}
// GetLastXmaFrameBitPosition: Calculates the bit offset of the last complete
// frame in an XMA block or set of blocks.
__inline DWORD GetLastXmaFrameBitPosition
(
__in_bcount(nXmaDataBytes) const BYTE* pXmaData, // Pointer to XMA block[s]
DWORD nXmaDataBytes, // Size of pXmaData in bytes
DWORD nStreamIndex // Stream within which to seek
)
{
const BYTE* pLastPacket;
DWORD nBytesToNextPacket;
DWORD nFrameBitOffset;
DWORD nFramesInLastPacket;
XMA2DEFS_ASSERT(pXmaData);
XMA2DEFS_ASSERT(nXmaDataBytes % XMA_BYTES_PER_PACKET == 0);
XMA2DEFS_ASSERT(nXmaDataBytes >= XMA_BYTES_PER_PACKET * (nStreamIndex + 1));
// Get the first XMA packet belonging to the desired stream, relying on the
// fact that the first packets for each stream are in consecutive order at
// the beginning of an XMA block.
pLastPacket = pXmaData + nStreamIndex * XMA_BYTES_PER_PACKET;
// Search for the last packet belonging to the desired stream
for (;;)
{
nBytesToNextPacket = XMA_BYTES_PER_PACKET * (GetXmaPacketSkipCount(pLastPacket) + 1);
XMA2DEFS_ASSERT(nBytesToNextPacket);
if (pLastPacket + nBytesToNextPacket + XMA_BYTES_PER_PACKET > pXmaData + nXmaDataBytes)
{
break; // The next packet would extend beyond the end of pXmaData
}
pLastPacket += nBytesToNextPacket;
}
// The last packet can sometimes have no seekable frames, in which case we
// have to use the previous one
if (GetXmaPacketFrameCount(pLastPacket) == 0)
{
pLastPacket -= nBytesToNextPacket;
}
// Found the last packet. Get the bit offset of its first frame.
nFrameBitOffset = XMA_PACKET_HEADER_BITS + GetXmaPacketFirstFrameOffsetInBits(pLastPacket);
// Traverse frames until we reach the last one
nFramesInLastPacket = GetXmaPacketFrameCount(pLastPacket);
while (--nFramesInLastPacket)
{
nFrameBitOffset += GetXmaFrameLengthInBits(pLastPacket, nFrameBitOffset);
}
// The bit offset to return is the number of bits from pXmaData to
// pLastPacket plus the offset of the last frame in this packet.
return (DWORD)(pLastPacket - pXmaData) * 8 + nFrameBitOffset;
}
// GetXmaDecodePositionForSample: Obtains the information needed to make the
// decoder generate audio starting at a given sample position relative to the
// beginning of the given XMA block: the bit offset of the appropriate frame,
// and the right subframe within that frame. This data can be passed directly
// to the XMAPlaybackSetDecodePosition function.
__inline HRESULT GetXmaDecodePositionForSample
(
__in_bcount(nXmaDataBytes) const BYTE* pXmaData, // Pointer to XMA block[s]
DWORD nXmaDataBytes, // Size of pXmaData in bytes
DWORD nStreamIndex, // Stream within which to seek
DWORD nDesiredSample, // Sample sought
__out DWORD* pnBitOffset, // Returns the bit offset within pXmaData of
// the frame containing the sample sought
__out DWORD* pnSubFrame // Returns the subframe containing the sample
)
{
DWORD nDesiredFrame = nDesiredSample / XMA_SAMPLES_PER_FRAME;
DWORD nSubFrame = (nDesiredSample % XMA_SAMPLES_PER_FRAME) / XMA_SAMPLES_PER_SUBFRAME;
DWORD nBitOffset = GetXmaFrameBitPosition(pXmaData, nXmaDataBytes, nStreamIndex, nDesiredFrame);
XMA2DEFS_ASSERT(pnBitOffset);
XMA2DEFS_ASSERT(pnSubFrame);
if (nBitOffset)
{
*pnBitOffset = nBitOffset;
*pnSubFrame = nSubFrame;
return S_OK;
}
else
{
return E_FAIL;
}
}
// GetXmaSampleRate: Obtains the legal XMA sample rate (24, 32, 44.1 or 48Khz)
// corresponding to a generic sample rate.
__inline DWORD GetXmaSampleRate(DWORD dwGeneralRate)
{
DWORD dwXmaRate = 48000; // Default XMA rate for all rates above 44100Hz
if (dwGeneralRate <= 24000) dwXmaRate = 24000;
else if (dwGeneralRate <= 32000) dwXmaRate = 32000;
else if (dwGeneralRate <= 44100) dwXmaRate = 44100;
return dwXmaRate;
}
// Functions to convert between WAVEFORMATEXTENSIBLE channel masks (combinations
// of the SPEAKER_xxx flags defined in audiodefs.h) and XMA channel masks (which
// are limited to eight possible speaker positions: left, right, center, low
// frequency, side left, side right, back left and back right).
__inline DWORD GetStandardChannelMaskFromXmaMask(BYTE bXmaMask)
{
DWORD dwStandardMask = 0;
if (bXmaMask & XMA_SPEAKER_LEFT) dwStandardMask |= SPEAKER_FRONT_LEFT;
if (bXmaMask & XMA_SPEAKER_RIGHT) dwStandardMask |= SPEAKER_FRONT_RIGHT;
if (bXmaMask & XMA_SPEAKER_CENTER) dwStandardMask |= SPEAKER_FRONT_CENTER;
if (bXmaMask & XMA_SPEAKER_LFE) dwStandardMask |= SPEAKER_LOW_FREQUENCY;
if (bXmaMask & XMA_SPEAKER_LEFT_SURROUND) dwStandardMask |= SPEAKER_SIDE_LEFT;
if (bXmaMask & XMA_SPEAKER_RIGHT_SURROUND) dwStandardMask |= SPEAKER_SIDE_RIGHT;
if (bXmaMask & XMA_SPEAKER_LEFT_BACK) dwStandardMask |= SPEAKER_BACK_LEFT;
if (bXmaMask & XMA_SPEAKER_RIGHT_BACK) dwStandardMask |= SPEAKER_BACK_RIGHT;
return dwStandardMask;
}
__inline BYTE GetXmaChannelMaskFromStandardMask(DWORD dwStandardMask)
{
BYTE bXmaMask = 0;
if (dwStandardMask & SPEAKER_FRONT_LEFT) bXmaMask |= XMA_SPEAKER_LEFT;
if (dwStandardMask & SPEAKER_FRONT_RIGHT) bXmaMask |= XMA_SPEAKER_RIGHT;
if (dwStandardMask & SPEAKER_FRONT_CENTER) bXmaMask |= XMA_SPEAKER_CENTER;
if (dwStandardMask & SPEAKER_LOW_FREQUENCY) bXmaMask |= XMA_SPEAKER_LFE;
if (dwStandardMask & SPEAKER_SIDE_LEFT) bXmaMask |= XMA_SPEAKER_LEFT_SURROUND;
if (dwStandardMask & SPEAKER_SIDE_RIGHT) bXmaMask |= XMA_SPEAKER_RIGHT_SURROUND;
if (dwStandardMask & SPEAKER_BACK_LEFT) bXmaMask |= XMA_SPEAKER_LEFT_BACK;
if (dwStandardMask & SPEAKER_BACK_RIGHT) bXmaMask |= XMA_SPEAKER_RIGHT_BACK;
return bXmaMask;
}
// LocalizeXma2Format: Modifies a XMA2WAVEFORMATEX structure in place to comply
// with the current platform's byte-ordering rules (little- or big-endian).
__inline HRESULT LocalizeXma2Format(__inout XMA2WAVEFORMATEX* pXma2Format)
{
#define XMASWAP2BYTES(n) ((WORD)(((n) >> 8) | (((n) & 0xff) << 8)))
#define XMASWAP4BYTES(n) ((DWORD)((n) >> 24 | (n) << 24 | ((n) & 0xff00) << 8 | ((n) & 0xff0000) >> 8))
if (pXma2Format->wfx.wFormatTag == WAVE_FORMAT_XMA2)
{
return S_OK;
}
else if (XMASWAP2BYTES(pXma2Format->wfx.wFormatTag) == WAVE_FORMAT_XMA2)
{
pXma2Format->wfx.wFormatTag = XMASWAP2BYTES(pXma2Format->wfx.wFormatTag);
pXma2Format->wfx.nChannels = XMASWAP2BYTES(pXma2Format->wfx.nChannels);
pXma2Format->wfx.nSamplesPerSec = XMASWAP4BYTES(pXma2Format->wfx.nSamplesPerSec);
pXma2Format->wfx.nAvgBytesPerSec = XMASWAP4BYTES(pXma2Format->wfx.nAvgBytesPerSec);
pXma2Format->wfx.nBlockAlign = XMASWAP2BYTES(pXma2Format->wfx.nBlockAlign);
pXma2Format->wfx.wBitsPerSample = XMASWAP2BYTES(pXma2Format->wfx.wBitsPerSample);
pXma2Format->wfx.cbSize = XMASWAP2BYTES(pXma2Format->wfx.cbSize);
pXma2Format->NumStreams = XMASWAP2BYTES(pXma2Format->NumStreams);
pXma2Format->ChannelMask = XMASWAP4BYTES(pXma2Format->ChannelMask);
pXma2Format->SamplesEncoded = XMASWAP4BYTES(pXma2Format->SamplesEncoded);
pXma2Format->BytesPerBlock = XMASWAP4BYTES(pXma2Format->BytesPerBlock);
pXma2Format->PlayBegin = XMASWAP4BYTES(pXma2Format->PlayBegin);
pXma2Format->PlayLength = XMASWAP4BYTES(pXma2Format->PlayLength);
pXma2Format->LoopBegin = XMASWAP4BYTES(pXma2Format->LoopBegin);
pXma2Format->LoopLength = XMASWAP4BYTES(pXma2Format->LoopLength);
pXma2Format->BlockCount = XMASWAP2BYTES(pXma2Format->BlockCount);
return S_OK;
}
else
{
return E_FAIL; // Not a recognizable XMA2 format
}
#undef XMASWAP2BYTES
#undef XMASWAP4BYTES
}
#endif // #ifndef __XMA2DEFS_INCLUDED__