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/*---- DXhead.h --------------------------------------------
decoder MPEG Layer III
handle Xing header
Copyright 1998 Xing Technology Corp.
-----------------------------------------------------------*/
/* A Xing header may be present in the ancillary
* data field of the first frame of an mp3 bitstream
* The Xing 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 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 Xing header data */
int frames; /* total bit stream frames from Xing header data */
int bytes; /* total bit stream bytes from Xing header data */
int vbr_scale; /* encoded vbr scale from Xing header data */
unsigned char *toc; /* pointer to unsigned char toc_buffer[100] */
/* may be NULL if toc not desired */
}
XHEADDATA;
int mpg123_get_xing_header(XHEADDATA * X, unsigned char *buf);
/* return 0=fail, 1=success
* X structure to receive header data (output)
* buf bitstream input
*/
int mpg123_seek_point(unsigned char TOC[100], int file_bytes, float percent);
/* return seekpoint in bytes (may be at eof if percent=100.0)
* TOC = table of contents from Xing header
* file_bytes = number of bytes in mp3 file
* percent = play time percentage of total playtime. May be
* fractional (e.g. 87.245)
*/
int mpg123_stream_check_for_xing_header(struct frame *fr, XHEADDATA * xhead);
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