mp3common.h

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00035 
00036 /**************************************************************************************
00037  * Fixed-point MP3 decoder
00038  * Jon Recker (jrecker@real.com), Ken Cooke (kenc@real.com)
00039  * June 2003
00040  *
00041  * mp3common.h - implementation-independent API's, datatypes, and definitions
00042  **************************************************************************************/
00043 
00044 #ifndef _MP3COMMON_H
00045 #define _MP3COMMON_H
00046 
00047 #include "mp3dec.h"
00048 #include "statname.h"   /* do name-mangling for static linking */
00049 
00050 #define MAX_SCFBD       4       /* max scalefactor bands per channel */
00051 #define NGRANS_MPEG1    2
00052 #define NGRANS_MPEG2    1
00053 
00054 /* 11-bit syncword if MPEG 2.5 extensions are enabled */
00055 #define SYNCWORDH       0xff
00056 #define SYNCWORDL       0xe0
00057 
00058 /* 12-bit syncword if MPEG 1,2 only are supported 
00059  * #define  SYNCWORDH       0xff
00060  * #define  SYNCWORDL       0xf0
00061  */
00062 
00063 typedef struct _MP3DecInfo {
00064     /* pointers to platform-specific data structures */
00065     void *FrameHeaderPS;
00066     void *SideInfoPS;
00067     void *ScaleFactorInfoPS;
00068     void *HuffmanInfoPS;
00069     void *DequantInfoPS;
00070     void *IMDCTInfoPS;
00071     void *SubbandInfoPS;
00072 
00073     /* buffer which must be large enough to hold largest possible main_data section */
00074     unsigned char mainBuf[MAINBUF_SIZE];
00075 
00076     /* special info for "free" bitrate files */
00077     int freeBitrateFlag;
00078     int freeBitrateSlots;
00079 
00080     /* user-accessible info */
00081     int bitrate;
00082     int nChans;
00083     int samprate;
00084     int nGrans;             /* granules per frame */
00085     int nGranSamps;         /* samples per granule */
00086     int nSlots;
00087     int layer;
00088     MPEGVersion version;
00089 
00090     int mainDataBegin;
00091     int mainDataBytes;
00092 
00093     int part23Length[MAX_NGRAN][MAX_NCHAN];
00094 
00095 } MP3DecInfo;
00096 
00097 typedef struct _SFBandTable {
00098     short l[23];
00099     short s[14];
00100 } SFBandTable;
00101 
00102 /* decoder functions which must be implemented for each platform */
00103 MP3DecInfo *AllocateBuffers(void);
00104 void FreeBuffers(MP3DecInfo *mp3DecInfo);
00105 int CheckPadBit(MP3DecInfo *mp3DecInfo);
00106 int UnpackFrameHeader(MP3DecInfo *mp3DecInfo, unsigned char *buf);
00107 int UnpackSideInfo(MP3DecInfo *mp3DecInfo, unsigned char *buf);
00108 int DecodeHuffman(MP3DecInfo *mp3DecInfo, unsigned char *buf, int *bitOffset, int huffBlockBits, int gr, int ch);
00109 int Dequantize(MP3DecInfo *mp3DecInfo, int gr);
00110 int IMDCT(MP3DecInfo *mp3DecInfo, int gr, int ch);
00111 int UnpackScaleFactors(MP3DecInfo *mp3DecInfo, unsigned char *buf, int *bitOffset, int bitsAvail, int gr, int ch);
00112 int Subband(MP3DecInfo *mp3DecInfo, short *pcmBuf);
00113 
00114 /* mp3tabs.c - global ROM tables */
00115 extern const int samplerateTab[3][3];
00116 extern const short bitrateTab[3][3][15];
00117 extern const short samplesPerFrameTab[3][3];
00118 extern const short bitsPerSlotTab[3];
00119 extern const short sideBytesTab[3][2];
00120 extern const short slotTab[3][3][15];
00121 extern const SFBandTable sfBandTable[3][3];
00122 
00123 #endif  /* _MP3COMMON_H */