mpegdec.h

mp3解码源代码

/****************************************************************************/

/*
 *	mpegdec.h -- MPEG Audio decoder definitions.
 *
 *	Author  :   St閜hane TAVENARD
 *
 *	(C) Copyright 1997-1998 St閜hane TAVENARD
 *	    All Rights Reserved
 *	
 *	This program is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU General Public License as published by
 *	the Free Software Foundation; either version 2 of the License, or
 *	(at your option) any later version.
 *	
 *	This program 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 General Public License for more details.
 *	
 *	You should have received a copy of the GNU General Public License
 *	along with this program; if not, write to the Free Software
 *	Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/****************************************************************************/
#ifndef MPEGDEC_H
#define MPEGDEC_H
/****************************************************************************/

#include "bitstr.h"

/*
 *	Controls for decoding
 */

/*
 *	Qualities
 */
#define MPEGDEC_QUALITY_LOW	0
#define MPEGDEC_QUALITY_MEDIUM	1
#define MPEGDEC_QUALITY_HIGH	2


/*
 *	 Specify how to access the bitstream
 *	   open:  open the bitstream, should return your file handle
 *		  (or NULL if failed), stream_size is the total size of
 *		  the stream (in bytes, could be 0 if unknown)
 *	   close: close the bitstream
 *	   read:  read bytes from bitstream, return # of bytes read
 *		  or <=0 if EOF
 *	   seek:  seek to an absolute byte position inside the bitstream,
 *		  return 0 if Ok
 */
typedef struct {
	INT32	(*open)(char *stream_name, INT32 buffer_size, INT32 *stream_size);
	void	(*close)(INT32 handle);
	INT32	(*read)(INT32 handle, void *buffer, INT32 num_bytes);
	int	(*seek)(INT32 handle, INT32 abs_byte_seek_pos);
} MPEGDEC_ACCESS;

/*
 *	Decoding output
 */
typedef struct {
	INT16	freq_div;	// 1, 2 or 4
	INT16	quality;	// 0 (low) .. 2 (high)
	INT32	freq_max;	// for automatic freq_div (if mono_freq_div==0)
} MPEGDEC_OUTPUT;

/*
 *	 Decoding layer
 */
typedef struct {
	INT16		force_mono; // 1 = stereo stream in mono, 0 otherwise
	MPEGDEC_OUTPUT	mono;	    // mono settings
	MPEGDEC_OUTPUT	stereo;	    // stereo settings
} MPEGDEC_LAYER;

/*
 *	Control structure of MPEG Audio decoding
 */
typedef struct {
	MPEGDEC_ACCESS	*bs_access;	// NULL for default access (file I/O)
					// or give your own bitstream access
	MPEGDEC_LAYER	layer_1_2;	// Layer I & II settings (#8)
	MPEGDEC_LAYER	layer_3;	// Layer III settings (#8)
	INT16		check_mpeg;	// 1 to check for mpeg audio validity
					// at start of stream, 0 otherwise
	INT32		stream_buffer_size; // #7: size of bitstream buffer
					// in bytes (0 -> default size)
					// NOTE: stream_buffer_size must be
					// multiple of 4 bytes
} MPEGDEC_CTRL;

/*
 *	Modes
 */
#define MPEGDEC_MODE_STEREO	0
#define MPEGDEC_MODE_J_STEREO	1
#define MPEGDEC_MODE_DUAL	2
#define MPEGDEC_MODE_MONO	3

typedef struct {
	// Stream info
	INT16	norm;         // 1 or 2
	INT16	layer;        // 1..3
	INT16	mode;         // 0..3  (MPEGDEC_MODE_xxx)
	INT16	bitrate;      // in kbps
	INT32	frequency;    // in Hz
	INT16	channels;     // 1 or 2
	UINT32	ms_duration;  // stream duration in ms
	INT16	private_bit;  // 0 or 1
	INT16	copyright;    // 0 or 1
	INT16	original;     // 0 or 1
	// Decoding info according to MPEG control
	INT16	dec_channels;
	INT16	dec_quality;
	INT32	dec_frequency;
	// Private data
	void	*handle;
} MPEGDEC_STREAM;

#define MPEGDEC_MAX_CHANNELS	2    // Max channels
#define MPEGDEC_PCM_SIZE	1152 // Max samples per frame

/*
 *	Error codes.
 */
#define MPEGDEC_ERR_NONE	0
#define MPEGDEC_ERR_BASE	0
#define MPEGDEC_ERR_EOF		(MPEGDEC_ERR_BASE-1)
#define MPEGDEC_ERR_BADFRAME	(MPEGDEC_ERR_BASE-2)
#define MPEGDEC_ERR_MEM		(MPEGDEC_ERR_BASE-3)
#define MPEGDEC_ERR_NO_SYNC	(MPEGDEC_ERR_BASE-4)
#define MPEGDEC_ERR_BADVALUE	(MPEGDEC_ERR_BASE-5)

/*
 *	Exported functions.
 */
extern MPEGDEC_STREAM	*MPEGDEC_open(char *filename, MPEGDEC_CTRL *ctrl);

extern void	MPEGDEC_close(MPEGDEC_STREAM *mpds);
extern int	MPEGDEC_scale(MPEGDEC_STREAM *mpds, INT32 scale_percent);
extern INT32	MPEGDEC_decode_frame(MPEGDEC_STREAM *mpds,
			INT16 *pcm[MPEGDEC_MAX_CHANNELS]);
extern int	MPEGDEC_seek(MPEGDEC_STREAM *mpds, UINT32 ms_time_position);
extern int	MPEGDEC_time(MPEGDEC_STREAM *mpds, UINT32 *ms_time_position);
extern INT32	MPEGDEC_find_sync(INT8 *buffer, INT32 buffer_size);

/****************************************************************************/
#endif /* MPEGDEC_H */