vbrtag.h

音频编码

/*
 *	Xing VBR tagging for LAME.
 *
 *	Copyright (c) 1999 A.L. Faber
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifndef LAME_VRBTAG_H
#define LAME_VRBTAG_H

#include "lame.h"

#if HAVE_INTTYPES_H
# include <inttypes.h>
#else
# if HAVE_STDINT_H
#  include <stdint.h>
# endif
#endif

/* -----------------------------------------------------------
 * A Vbr header may be present in the ancillary
 * data field of the first frame of an mp3 bitstream
 * The Vbr header (optionally) contains
 *      frames      total number of audio frames in the bitstream
 *      bytes       total number of bytes in the bitstream
 *      toc         table of contents

 * toc (table of contents) gives seek points
 * for random access
 * the ith entry determines the seek point for
 * i-percent duration
 * seek point in bytes = (toc[i]/256.0) * total_bitstream_bytes
 * e.g. half duration seek point = (toc[50]/256.0) * total_bitstream_bytes
 */


#define FRAMES_FLAG     0x0001
#define BYTES_FLAG      0x0002
#define TOC_FLAG        0x0004
#define VBR_SCALE_FLAG  0x0008

#define NUMTOCENTRIES 100

#define FRAMES_AND_BYTES (FRAMES_FLAG | BYTES_FLAG)


 
/*structure to receive extracted header */
/* toc may be NULL*/
typedef struct
{
  int		h_id;			/* from MPEG header, 0=MPEG2, 1=MPEG1 */
  int		samprate;		/* determined from MPEG header */
  int		flags;			/* from Vbr header data */
  int		frames;			/* total bit stream frames from Vbr header data */
  int		bytes;			/* total bit stream bytes from Vbr header data*/
  int		vbr_scale;		/* encoded vbr scale from Vbr header data*/
  unsigned char	toc[NUMTOCENTRIES];	/* may be NULL if toc not desired*/
  int           headersize;             /* size of VBR header, in bytes */
  int           enc_delay;              /* encoder delay */
  int           enc_padding;            /* encoder paddign added at end of stream */
}   VBRTAGDATA;

int CheckVbrTag(unsigned char *buf);
int GetVbrTag(VBRTAGDATA *pTagData,  unsigned char *buf);

int SeekPoint(unsigned char TOC[NUMTOCENTRIES], int file_bytes, float percent);
int InitVbrTag(lame_global_flags *gfp);
int PutVbrTag(lame_global_flags *gfp,FILE *fid,int nVbrScale);
int PutLameVBR(lame_global_flags *gfp, FILE *fpStream, uint8_t *pbtStreamBuffer, uint32_t id3v2size,  uint16_t crc);
void AddVbrFrame(lame_global_flags *gfp);
void UpdateMusicCRC(uint16_t *crc,unsigned char *buffer, int size);

#endif