390 lines
14 KiB
C
390 lines
14 KiB
C
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: RCSL 1.0/RPSL 1.0
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*
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* Portions Copyright (c) 1995-2002 RealNetworks, Inc. All Rights Reserved.
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*
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* The contents of this file, and the files included with this file, are
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* subject to the current version of the RealNetworks Public Source License
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* Version 1.0 (the "RPSL") available at
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* http://www.helixcommunity.org/content/rpsl unless you have licensed
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* the file under the RealNetworks Community Source License Version 1.0
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* (the "RCSL") available at http://www.helixcommunity.org/content/rcsl,
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* in which case the RCSL will apply. You may also obtain the license terms
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* directly from RealNetworks. You may not use this file except in
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* compliance with the RPSL or, if you have a valid RCSL with RealNetworks
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* applicable to this file, the RCSL. Please see the applicable RPSL or
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* RCSL for the rights, obligations and limitations governing use of the
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* contents of the file.
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*
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* This file is part of the Helix DNA Technology. RealNetworks is the
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* developer of the Original Code and owns the copyrights in the portions
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* it created.
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*
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* This file, and the files included with this file, is distributed and made
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* available on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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* EXPRESS OR IMPLIED, AND REALNETWORKS HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
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*
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* Technology Compatibility Kit Test Suite(s) Location:
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* http://www.helixcommunity.org/content/tck
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*
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* Contributor(s):
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*
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* ***** END LICENSE BLOCK ***** */
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/**************************************************************************************
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* Fixed-point MP3 decoder
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* Jon Recker (jrecker@real.com), Ken Cooke (kenc@real.com)
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* June 2003
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*
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* bitstream.c - bitstream unpacking, frame header parsing, side info parsing
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**************************************************************************************/
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#include "coder.h"
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#include "assembly.h"
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/**************************************************************************************
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* Function: SetBitstreamPointer
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*
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* Description: initialize bitstream reader
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*
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* Inputs: pointer to BitStreamInfo struct
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* number of bytes in bitstream
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* pointer to byte-aligned buffer of data to read from
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*
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* Outputs: filled bitstream info struct
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*
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* Return: none
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**************************************************************************************/
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void SetBitstreamPointer(BitStreamInfo *bsi, int nBytes, unsigned char *buf)
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{
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/* init bitstream */
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bsi->bytePtr = buf;
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bsi->iCache = 0; /* 4-byte unsigned int */
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bsi->cachedBits = 0; /* i.e. zero bits in cache */
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bsi->nBytes = nBytes;
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}
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/**************************************************************************************
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* Function: RefillBitstreamCache
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*
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* Description: read new data from bitstream buffer into bsi cache
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*
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* Inputs: pointer to initialized BitStreamInfo struct
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*
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* Outputs: updated bitstream info struct
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*
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* Return: none
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*
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* Notes: only call when iCache is completely drained (resets bitOffset to 0)
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* always loads 4 new bytes except when bsi->nBytes < 4 (end of buffer)
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* stores data as big-endian in cache, regardless of machine endian-ness
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*
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* TODO: optimize for ARM
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* possibly add little/big-endian modes for doing 32-bit loads
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**************************************************************************************/
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static __inline void RefillBitstreamCache(BitStreamInfo *bsi)
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{
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int nBytes = bsi->nBytes;
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/* optimize for common case, independent of machine endian-ness */
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if (nBytes >= 4) {
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bsi->iCache = (*bsi->bytePtr++) << 24;
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bsi->iCache |= (*bsi->bytePtr++) << 16;
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bsi->iCache |= (*bsi->bytePtr++) << 8;
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bsi->iCache |= (*bsi->bytePtr++);
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bsi->cachedBits = 32;
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bsi->nBytes -= 4;
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} else {
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bsi->iCache = 0;
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while (nBytes--) {
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bsi->iCache |= (*bsi->bytePtr++);
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bsi->iCache <<= 8;
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}
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bsi->iCache <<= ((3 - bsi->nBytes)*8);
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bsi->cachedBits = 8*bsi->nBytes;
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bsi->nBytes = 0;
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}
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}
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/**************************************************************************************
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* Function: GetBits
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*
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* Description: get bits from bitstream, advance bitstream pointer
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*
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* Inputs: pointer to initialized BitStreamInfo struct
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* number of bits to get from bitstream
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*
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* Outputs: updated bitstream info struct
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*
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* Return: the next nBits bits of data from bitstream buffer
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*
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* Notes: nBits must be in range [0, 31], nBits outside this range masked by 0x1f
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* for speed, does not indicate error if you overrun bit buffer
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* if nBits = 0, returns 0 (useful for scalefactor unpacking)
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*
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* TODO: optimize for ARM
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**************************************************************************************/
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unsigned int GetBits(BitStreamInfo *bsi, int nBits)
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{
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unsigned int data, lowBits;
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nBits &= 0x1f; /* nBits mod 32 to avoid unpredictable results like >> by negative amount */
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data = bsi->iCache >> (31 - nBits); /* unsigned >> so zero-extend */
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data >>= 1; /* do as >> 31, >> 1 so that nBits = 0 works okay (returns 0) */
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bsi->iCache <<= nBits; /* left-justify cache */
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bsi->cachedBits -= nBits; /* how many bits have we drawn from the cache so far */
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/* if we cross an int boundary, refill the cache */
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if (bsi->cachedBits < 0) {
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lowBits = -bsi->cachedBits;
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RefillBitstreamCache(bsi);
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data |= bsi->iCache >> (32 - lowBits); /* get the low-order bits */
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bsi->cachedBits -= lowBits; /* how many bits have we drawn from the cache so far */
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bsi->iCache <<= lowBits; /* left-justify cache */
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}
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return data;
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}
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/**************************************************************************************
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* Function: CalcBitsUsed
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*
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* Description: calculate how many bits have been read from bitstream
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*
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* Inputs: pointer to initialized BitStreamInfo struct
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* pointer to start of bitstream buffer
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* bit offset into first byte of startBuf (0-7)
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*
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* Outputs: none
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*
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* Return: number of bits read from bitstream, as offset from startBuf:startOffset
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**************************************************************************************/
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int CalcBitsUsed(BitStreamInfo *bsi, unsigned char *startBuf, int startOffset)
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{
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int bitsUsed;
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bitsUsed = (bsi->bytePtr - startBuf) * 8;
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bitsUsed -= bsi->cachedBits;
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bitsUsed -= startOffset;
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return bitsUsed;
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}
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/**************************************************************************************
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* Function: CheckPadBit
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*
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* Description: check whether padding byte is present in an MP3 frame
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*
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* Inputs: MP3DecInfo struct with valid FrameHeader struct
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* (filled by UnpackFrameHeader())
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*
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* Outputs: none
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*
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* Return: 1 if pad bit is set, 0 if not, -1 if null input pointer
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**************************************************************************************/
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int CheckPadBit(MP3DecInfo *mp3DecInfo)
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{
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FrameHeader *fh;
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/* validate pointers */
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if (!mp3DecInfo || !mp3DecInfo->FrameHeaderPS)
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return -1;
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fh = ((FrameHeader *)(mp3DecInfo->FrameHeaderPS));
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return (fh->paddingBit ? 1 : 0);
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}
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/**************************************************************************************
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* Function: UnpackFrameHeader
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*
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* Description: parse the fields of the MP3 frame header
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*
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* Inputs: buffer pointing to a complete MP3 frame header (4 bytes, plus 2 if CRC)
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*
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* Outputs: filled frame header info in the MP3DecInfo structure
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* updated platform-specific FrameHeader struct
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*
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* Return: length (in bytes) of frame header (for caller to calculate offset to
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* first byte following frame header)
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* -1 if null frameHeader or invalid header
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*
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* TODO: check for valid modes, depending on capabilities of decoder
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* test CRC on actual stream (verify no endian problems)
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**************************************************************************************/
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int UnpackFrameHeader(MP3DecInfo *mp3DecInfo, unsigned char *buf)
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{
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int verIdx;
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FrameHeader *fh;
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/* validate pointers and sync word */
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if (!mp3DecInfo || !mp3DecInfo->FrameHeaderPS || (buf[0] & SYNCWORDH) != SYNCWORDH || (buf[1] & SYNCWORDL) != SYNCWORDL)
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return -1;
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fh = ((FrameHeader *)(mp3DecInfo->FrameHeaderPS));
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/* read header fields - use bitmasks instead of GetBits() for speed, since format never varies */
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verIdx = (buf[1] >> 3) & 0x03;
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fh->ver = (MPEGVersion)( verIdx == 0 ? MPEG25 : ((verIdx & 0x01) ? MPEG1 : MPEG2) );
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fh->layer = 4 - ((buf[1] >> 1) & 0x03); /* easy mapping of index to layer number, 4 = error */
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fh->crc = 1 - ((buf[1] >> 0) & 0x01);
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fh->brIdx = (buf[2] >> 4) & 0x0f;
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fh->srIdx = (buf[2] >> 2) & 0x03;
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fh->paddingBit = (buf[2] >> 1) & 0x01;
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fh->privateBit = (buf[2] >> 0) & 0x01;
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fh->sMode = (StereoMode)((buf[3] >> 6) & 0x03); /* maps to correct enum (see definition) */
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fh->modeExt = (buf[3] >> 4) & 0x03;
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fh->copyFlag = (buf[3] >> 3) & 0x01;
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fh->origFlag = (buf[3] >> 2) & 0x01;
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fh->emphasis = (buf[3] >> 0) & 0x03;
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/* check parameters to avoid indexing tables with bad values */
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if (fh->srIdx == 3 || fh->layer == 4 || fh->brIdx == 15)
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return -1;
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fh->sfBand = &sfBandTable[fh->ver][fh->srIdx]; /* for readability (we reference sfBandTable many times in decoder) */
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if (fh->sMode != Joint) /* just to be safe (dequant, stproc check fh->modeExt) */
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fh->modeExt = 0;
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/* init user-accessible data */
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mp3DecInfo->nChans = (fh->sMode == Mono ? 1 : 2);
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mp3DecInfo->samprate = samplerateTab[fh->ver][fh->srIdx];
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mp3DecInfo->nGrans = (fh->ver == MPEG1 ? NGRANS_MPEG1 : NGRANS_MPEG2);
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mp3DecInfo->nGranSamps = ((int)samplesPerFrameTab[fh->ver][fh->layer - 1]) / mp3DecInfo->nGrans;
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mp3DecInfo->layer = fh->layer;
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mp3DecInfo->version = fh->ver;
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/* get bitrate and nSlots from table, unless brIdx == 0 (free mode) in which case caller must figure it out himself
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* question - do we want to overwrite mp3DecInfo->bitrate with 0 each time if it's free mode, and
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* copy the pre-calculated actual free bitrate into it in mp3dec.c (according to the spec,
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* this shouldn't be necessary, since it should be either all frames free or none free)
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*/
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if (fh->brIdx) {
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mp3DecInfo->bitrate = ((int)bitrateTab[fh->ver][fh->layer - 1][fh->brIdx]) * 1000;
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/* nSlots = total frame bytes (from table) - sideInfo bytes - header - CRC (if present) + pad (if present) */
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mp3DecInfo->nSlots = (int)slotTab[fh->ver][fh->srIdx][fh->brIdx] -
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(int)sideBytesTab[fh->ver][(fh->sMode == Mono ? 0 : 1)] -
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4 - (fh->crc ? 2 : 0) + (fh->paddingBit ? 1 : 0);
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}
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/* load crc word, if enabled, and return length of frame header (in bytes) */
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if (fh->crc) {
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fh->CRCWord = ((int)buf[4] << 8 | (int)buf[5] << 0);
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return 6;
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} else {
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fh->CRCWord = 0;
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return 4;
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}
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}
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/**************************************************************************************
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* Function: UnpackSideInfo
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*
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* Description: parse the fields of the MP3 side info header
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*
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* Inputs: MP3DecInfo structure filled by UnpackFrameHeader()
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* buffer pointing to the MP3 side info data
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*
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* Outputs: updated mainDataBegin in MP3DecInfo struct
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* updated private (platform-specific) SideInfo struct
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*
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* Return: length (in bytes) of side info data
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* -1 if null input pointers
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**************************************************************************************/
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int UnpackSideInfo(MP3DecInfo *mp3DecInfo, unsigned char *buf)
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{
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int gr, ch, bd, nBytes;
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BitStreamInfo bitStreamInfo, *bsi;
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FrameHeader *fh;
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SideInfo *si;
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SideInfoSub *sis;
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/* validate pointers and sync word */
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if (!mp3DecInfo || !mp3DecInfo->FrameHeaderPS || !mp3DecInfo->SideInfoPS)
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return -1;
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fh = ((FrameHeader *)(mp3DecInfo->FrameHeaderPS));
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si = ((SideInfo *)(mp3DecInfo->SideInfoPS));
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bsi = &bitStreamInfo;
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if (fh->ver == MPEG1) {
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/* MPEG 1 */
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nBytes = (fh->sMode == Mono ? SIBYTES_MPEG1_MONO : SIBYTES_MPEG1_STEREO);
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SetBitstreamPointer(bsi, nBytes, buf);
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si->mainDataBegin = GetBits(bsi, 9);
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si->privateBits = GetBits(bsi, (fh->sMode == Mono ? 5 : 3));
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for (ch = 0; ch < mp3DecInfo->nChans; ch++)
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for (bd = 0; bd < MAX_SCFBD; bd++)
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si->scfsi[ch][bd] = GetBits(bsi, 1);
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} else {
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/* MPEG 2, MPEG 2.5 */
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nBytes = (fh->sMode == Mono ? SIBYTES_MPEG2_MONO : SIBYTES_MPEG2_STEREO);
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SetBitstreamPointer(bsi, nBytes, buf);
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si->mainDataBegin = GetBits(bsi, 8);
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si->privateBits = GetBits(bsi, (fh->sMode == Mono ? 1 : 2));
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}
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for(gr =0; gr < mp3DecInfo->nGrans; gr++) {
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for (ch = 0; ch < mp3DecInfo->nChans; ch++) {
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sis = &si->sis[gr][ch]; /* side info subblock for this granule, channel */
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sis->part23Length = GetBits(bsi, 12);
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sis->nBigvals = GetBits(bsi, 9);
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sis->globalGain = GetBits(bsi, 8);
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sis->sfCompress = GetBits(bsi, (fh->ver == MPEG1 ? 4 : 9));
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sis->winSwitchFlag = GetBits(bsi, 1);
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|
if(sis->winSwitchFlag) {
|
||
|
|
/* this is a start, stop, short, or mixed block */
|
||
|
|
sis->blockType = GetBits(bsi, 2); /* 0 = normal, 1 = start, 2 = short, 3 = stop */
|
||
|
|
sis->mixedBlock = GetBits(bsi, 1); /* 0 = not mixed, 1 = mixed */
|
||
|
|
sis->tableSelect[0] = GetBits(bsi, 5);
|
||
|
|
sis->tableSelect[1] = GetBits(bsi, 5);
|
||
|
|
sis->tableSelect[2] = 0; /* unused */
|
||
|
|
sis->subBlockGain[0] = GetBits(bsi, 3);
|
||
|
|
sis->subBlockGain[1] = GetBits(bsi, 3);
|
||
|
|
sis->subBlockGain[2] = GetBits(bsi, 3);
|
||
|
|
|
||
|
|
/* TODO - check logic */
|
||
|
|
if (sis->blockType == 0) {
|
||
|
|
/* this should not be allowed, according to spec */
|
||
|
|
sis->nBigvals = 0;
|
||
|
|
sis->part23Length = 0;
|
||
|
|
sis->sfCompress = 0;
|
||
|
|
} else if (sis->blockType == 2 && sis->mixedBlock == 0) {
|
||
|
|
/* short block, not mixed */
|
||
|
|
sis->region0Count = 8;
|
||
|
|
} else {
|
||
|
|
/* start, stop, or short-mixed */
|
||
|
|
sis->region0Count = 7;
|
||
|
|
}
|
||
|
|
sis->region1Count = 20 - sis->region0Count;
|
||
|
|
} else {
|
||
|
|
/* this is a normal block */
|
||
|
|
sis->blockType = 0;
|
||
|
|
sis->mixedBlock = 0;
|
||
|
|
sis->tableSelect[0] = GetBits(bsi, 5);
|
||
|
|
sis->tableSelect[1] = GetBits(bsi, 5);
|
||
|
|
sis->tableSelect[2] = GetBits(bsi, 5);
|
||
|
|
sis->region0Count = GetBits(bsi, 4);
|
||
|
|
sis->region1Count = GetBits(bsi, 3);
|
||
|
|
}
|
||
|
|
sis->preFlag = (fh->ver == MPEG1 ? GetBits(bsi, 1) : 0);
|
||
|
|
sis->sfactScale = GetBits(bsi, 1);
|
||
|
|
sis->count1TableSelect = GetBits(bsi, 1);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
mp3DecInfo->mainDataBegin = si->mainDataBegin; /* needed by main decode loop */
|
||
|
|
|
||
|
|
ASSERT(nBytes == CalcBitsUsed(bsi, buf, 0) >> 3);
|
||
|
|
|
||
|
|
return nBytes;
|
||
|
|
}
|
||
|
|
|