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API documentation for libmpg123, libout123, and libsyn123

Note: This API doc is automatically generated from the current development version that you can get via Subversion or as a daily snapshot from http://mpg123.org/snapshot. There may be differences (additions) compared to the latest stable release. See NEWS.libmpg123, NEWS.libout123, NEWS.libsyn123, and the overall NEWS file on libmpg123 versions and important changes between them.
Let me emphasize that the policy for the lib*123 family is to always stay backwards compatible -- only additions are planned (and it's not yet planned to change the plans;-).
mpg123 metadata handling

Classes

struct  mpg123_string
 
struct  mpg123_text
 
struct  mpg123_picture
 
struct  mpg123_id3v2
 
struct  mpg123_id3v1
 

Macros

#define MPG123_ID3   0x3
 
#define MPG123_NEW_ID3   0x1
 
#define MPG123_ICY   0xc
 
#define MPG123_NEW_ICY   0x4
 

Enumerations

enum  mpg123_text_encoding {
  mpg123_text_unknown = 0, mpg123_text_utf8 = 1,
  mpg123_text_latin1 = 2, mpg123_text_icy = 3,
  mpg123_text_cp1252 = 4, mpg123_text_utf16 = 5,
  mpg123_text_utf16bom = 6, mpg123_text_utf16be = 7,
  mpg123_text_max = 7
}
 
enum  mpg123_id3_enc {
  mpg123_id3_latin1 = 0, mpg123_id3_utf16bom = 1,
  mpg123_id3_utf16be = 2, mpg123_id3_utf8 = 3,
  mpg123_id3_enc_max = 3
}
 
enum  mpg123_id3_pic_type {
  mpg123_id3_pic_other = 0, mpg123_id3_pic_icon = 1,
  mpg123_id3_pic_other_icon = 2, mpg123_id3_pic_front_cover = 3,
  mpg123_id3_pic_back_cover = 4, mpg123_id3_pic_leaflet = 5,
  mpg123_id3_pic_media = 6, mpg123_id3_pic_lead = 7,
  mpg123_id3_pic_artist = 8, mpg123_id3_pic_conductor = 9,
  mpg123_id3_pic_orchestra = 10, mpg123_id3_pic_composer = 11,
  mpg123_id3_pic_lyricist = 12, mpg123_id3_pic_location = 13,
  mpg123_id3_pic_recording = 14, mpg123_id3_pic_performance = 15,
  mpg123_id3_pic_video = 16, mpg123_id3_pic_fish = 17,
  mpg123_id3_pic_illustration = 18, mpg123_id3_pic_artist_logo = 19,
  mpg123_id3_pic_publisher_logo = 20
}
 

Functions

MPG123_EXPORT mpg123_stringmpg123_new_string (const char *val)
 
MPG123_EXPORT void mpg123_delete_string (mpg123_string *sb)
 
MPG123_EXPORT void mpg123_init_string (mpg123_string *sb)
 
MPG123_EXPORT void mpg123_free_string (mpg123_string *sb)
 
MPG123_EXPORT int mpg123_resize_string (mpg123_string *sb, size_t news)
 
MPG123_EXPORT int mpg123_grow_string (mpg123_string *sb, size_t news)
 
MPG123_EXPORT int mpg123_copy_string (mpg123_string *from, mpg123_string *to)
 
MPG123_EXPORT int mpg123_move_string (mpg123_string *from, mpg123_string *to)
 
MPG123_EXPORT int mpg123_add_string (mpg123_string *sb, const char *stuff)
 
MPG123_EXPORT int mpg123_add_substring (mpg123_string *sb, const char *stuff, size_t from, size_t count)
 
MPG123_EXPORT int mpg123_set_string (mpg123_string *sb, const char *stuff)
 
MPG123_EXPORT int mpg123_set_substring (mpg123_string *sb, const char *stuff, size_t from, size_t count)
 
MPG123_EXPORT size_t mpg123_strlen (mpg123_string *sb, int utf8)
 
MPG123_EXPORT int mpg123_chomp_string (mpg123_string *sb)
 
MPG123_EXPORT int mpg123_same_string (mpg123_string *a, mpg123_string *b)
 
MPG123_EXPORT enum mpg123_text_encoding mpg123_enc_from_id3 (unsigned char id3_enc_byte)
 
MPG123_EXPORT int mpg123_store_utf8 (mpg123_string *sb, enum mpg123_text_encoding enc, const unsigned char *source, size_t source_size)
 
MPG123_EXPORT int mpg123_meta_check (mpg123_handle *mh)
 
MPG123_EXPORT void mpg123_meta_free (mpg123_handle *mh)
 
MPG123_EXPORT int mpg123_id3 (mpg123_handle *mh, mpg123_id3v1 **v1, mpg123_id3v2 **v2)
 
MPG123_EXPORT int mpg123_id3_raw (mpg123_handle *mh, unsigned char **v1, size_t *v1_size, unsigned char **v2, size_t *v2_size)
 
MPG123_EXPORT int mpg123_icy (mpg123_handle *mh, char **icy_meta)
 
MPG123_EXPORT char * mpg123_icy2utf8 (const char *icy_text)
 

Detailed Description

Functions to retrieve the metadata from MPEG Audio files and streams. Also includes string handling functions.

Macro Definition Documentation

◆ MPG123_ID3

#define MPG123_ID3   0x3

0011 There is some ID3 info. Also matches 0010 or NEW_ID3.

Definition at line 1480 of file mpg123.h.

◆ MPG123_NEW_ID3

#define MPG123_NEW_ID3   0x1

0001 There is ID3 info that changed since last call to mpg123_id3.

Definition at line 1481 of file mpg123.h.

◆ MPG123_ICY

#define MPG123_ICY   0xc

1100 There is some ICY info. Also matches 0100 or NEW_ICY.

Definition at line 1482 of file mpg123.h.

◆ MPG123_NEW_ICY

#define MPG123_NEW_ICY   0x4

0100 There is ICY info that changed since last call to mpg123_icy.

Definition at line 1483 of file mpg123.h.

Enumeration Type Documentation

◆ mpg123_text_encoding

The mpg123 text encodings. This contains encodings we encounter in ID3 tags or ICY meta info.

Enumerator
mpg123_text_unknown 

Unkown encoding... mpg123_id3_encoding can return that on invalid codes.

mpg123_text_utf8 

UTF-8

mpg123_text_latin1 

ISO-8859-1. Note that sometimes latin1 in ID3 is abused for totally different encodings.

mpg123_text_icy 

ICY metadata encoding, usually CP-1252 but we take it as UTF-8 if it qualifies as such.

mpg123_text_cp1252 

Really CP-1252 without any guessing.

mpg123_text_utf16 

Some UTF-16 encoding. The last of a set of leading BOMs (byte order mark) rules. When there is no BOM, big endian ordering is used. Note that UCS-2 qualifies as UTF-8 when you don't mess with the reserved code points. If you want to decode little endian data without BOM you need to prepend 0xff 0xfe yourself.

mpg123_text_utf16bom 

Just an alias for UTF-16, ID3v2 has this as distinct code.

mpg123_text_utf16be 

Another alias for UTF16 from ID3v2. Note, that, because of the mess that is reality, BOMs are used if encountered. There really is not much distinction between the UTF16 types for mpg123 One exception: Since this is seen in ID3v2 tags, leading null bytes are skipped for all other UTF16 types (we expect a BOM before real data there), not so for utf16be!

mpg123_text_max 

Placeholder for the maximum encoding value.

Definition at line 1338 of file mpg123.h.

◆ mpg123_id3_enc

The encoding byte values from ID3v2.

Enumerator
mpg123_id3_latin1 

Note: This sometimes can mean anything in practice...

mpg123_id3_utf16bom 

UTF16, UCS-2 ... it's all the same for practical purposes.

mpg123_id3_utf16be 

Big-endian UTF-16, BOM see note for mpg123_text_utf16be.

mpg123_id3_utf8 

Our lovely overly ASCII-compatible 8 byte encoding for the world.

mpg123_id3_enc_max 

Placeholder to check valid range of encoding byte.

Definition at line 1358 of file mpg123.h.

◆ mpg123_id3_pic_type

The picture type values from ID3v2.

Enumerator
mpg123_id3_pic_other 

see ID3v2 docs

mpg123_id3_pic_icon 

see ID3v2 docs

mpg123_id3_pic_other_icon 

see ID3v2 docs

mpg123_id3_pic_front_cover 

see ID3v2 docs

mpg123_id3_pic_back_cover 

see ID3v2 docs

mpg123_id3_pic_leaflet 

see ID3v2 docs

mpg123_id3_pic_media 

see ID3v2 docs

mpg123_id3_pic_lead 

see ID3v2 docs

mpg123_id3_pic_artist 

see ID3v2 docs

mpg123_id3_pic_conductor 

see ID3v2 docs

mpg123_id3_pic_orchestra 

see ID3v2 docs

mpg123_id3_pic_composer 

see ID3v2 docs

mpg123_id3_pic_lyricist 

see ID3v2 docs

mpg123_id3_pic_location 

see ID3v2 docs

mpg123_id3_pic_recording 

see ID3v2 docs

mpg123_id3_pic_performance 

see ID3v2 docs

mpg123_id3_pic_video 

see ID3v2 docs

mpg123_id3_pic_fish 

see ID3v2 docs

mpg123_id3_pic_illustration 

see ID3v2 docs

mpg123_id3_pic_artist_logo 

see ID3v2 docs

mpg123_id3_pic_publisher_logo 

see ID3v2 docs

Definition at line 1400 of file mpg123.h.

Function Documentation

◆ mpg123_new_string()

MPG123_EXPORT mpg123_string* mpg123_new_string ( const char *  val)

Allocate and intialize a new string.

Parameters
valoptional initial string value (can be NULL)

◆ mpg123_delete_string()

MPG123_EXPORT void mpg123_delete_string ( mpg123_string sb)

Free memory of contents and the string structure itself.

Parameters
sbstring handle

◆ mpg123_init_string()

MPG123_EXPORT void mpg123_init_string ( mpg123_string sb)

Initialize an existing mpg123_string structure to {NULL, 0, 0}. If you hand in a NULL pointer here, your program should crash. The other string functions are more forgiving, but this one here is too basic.

Parameters
sbstring handle (address of existing structure on your side)

◆ mpg123_free_string()

MPG123_EXPORT void mpg123_free_string ( mpg123_string sb)

Free-up memory of the contents of an mpg123_string (not the struct itself). This also calls mpg123_init_string() and hence is safe to be called repeatedly.

Parameters
sbstring handle

◆ mpg123_resize_string()

MPG123_EXPORT int mpg123_resize_string ( mpg123_string sb,
size_t  news 
)

Change the size of a mpg123_string

Parameters
sbstring handle
newsnew size in bytes
Returns
0 on error, 1 on success

◆ mpg123_grow_string()

MPG123_EXPORT int mpg123_grow_string ( mpg123_string sb,
size_t  news 
)

Increase size of a mpg123_string if necessary (it may stay larger). Note that the functions for adding and setting in current libmpg123 use this instead of mpg123_resize_string(). That way, you can preallocate memory and safely work afterwards with pieces.

Parameters
sbstring handle
newsnew minimum size
Returns
0 on error, 1 on success

◆ mpg123_copy_string()

MPG123_EXPORT int mpg123_copy_string ( mpg123_string from,
mpg123_string to 
)

Copy the contents of one mpg123_string string to another. Yes the order of arguments is reversed compated to memcpy().

Parameters
fromstring handle
tostring handle
Returns
0 on error, 1 on success

◆ mpg123_move_string()

MPG123_EXPORT int mpg123_move_string ( mpg123_string from,
mpg123_string to 
)

Move the contents of one mpg123_string string to another. This frees any memory associated with the target and moves over the pointers from the source, leaving the source without content after that. The only possible error is that you hand in NULL pointers. If you handed in a valid source, its contents will be gone, even if there was no target to move to. If you hand in a valid target, its original contents will also always be gone, to be replaced with the source's contents if there was some.

Parameters
fromsource string handle
totarget string handle
Returns
0 on error, 1 on success

◆ mpg123_add_string()

MPG123_EXPORT int mpg123_add_string ( mpg123_string sb,
const char *  stuff 
)

Append a C-String to an mpg123_string

Parameters
sbstring handle
stuffto append
Returns
0 on error, 1 on success

◆ mpg123_add_substring()

MPG123_EXPORT int mpg123_add_substring ( mpg123_string sb,
const char *  stuff,
size_t  from,
size_t  count 
)

Append a C-substring to an mpg123 string

Parameters
sbstring handle
stuffcontent to copy
fromoffset to copy from
countnumber of characters to copy (a null-byte is always appended)
Returns
0 on error, 1 on success

◆ mpg123_set_string()

MPG123_EXPORT int mpg123_set_string ( mpg123_string sb,
const char *  stuff 
)

Set the content of a mpg123_string to a C-string

Parameters
sbstring handle
stuffcontent to copy
Returns
0 on error, 1 on success

◆ mpg123_set_substring()

MPG123_EXPORT int mpg123_set_substring ( mpg123_string sb,
const char *  stuff,
size_t  from,
size_t  count 
)

Set the content of a mpg123_string to a C-substring

Parameters
sbstring handle
stuffthe future content
fromoffset to copy from
countnumber of characters to copy (a null-byte is always appended)
Returns
0 on error, 1 on success

◆ mpg123_strlen()

MPG123_EXPORT size_t mpg123_strlen ( mpg123_string sb,
int  utf8 
)

Count characters in a mpg123 string (non-null bytes or Unicode points). This function is of limited use, as it does just count code points encoded in an UTF-8 string, only loosely related to the count of visible characters. Get your full Unicode handling support elsewhere.

Parameters
sbstring handle
utf8a flag to tell if the string is in utf8 encoding
Returns
character count

◆ mpg123_chomp_string()

MPG123_EXPORT int mpg123_chomp_string ( mpg123_string sb)

Remove trailing \r and \n, if present.

Parameters
sbstring handle
Returns
0 on error, 1 on success

◆ mpg123_same_string()

MPG123_EXPORT int mpg123_same_string ( mpg123_string a,
mpg123_string b 
)

Determine if two strings contain the same data. This only returns 1 if both given handles are non-NULL and if they are filled with the same bytes.

Parameters
afirst string handle
bsecond string handle
Returns
0 for different strings, 1 for identical

◆ mpg123_enc_from_id3()

MPG123_EXPORT enum mpg123_text_encoding mpg123_enc_from_id3 ( unsigned char  id3_enc_byte)

Convert ID3 encoding byte to mpg123 encoding index.

Parameters
id3_enc_bytethe ID3 encoding code
Returns
the mpg123 encoding index

◆ mpg123_store_utf8()

MPG123_EXPORT int mpg123_store_utf8 ( mpg123_string sb,
enum mpg123_text_encoding  enc,
const unsigned char *  source,
size_t  source_size 
)

Store text data in string, after converting to UTF-8 from indicated encoding A prominent error can be that you provided an unknown encoding value, or this build of libmpg123 lacks support for certain encodings (ID3 or ICY stuff missing). Also, you might want to take a bit of care with preparing the data; for example, strip leading zeroes (I have seen that).

Parameters
sbtarget string
encmpg123 text encoding value
sourcesource buffer with plain unsigned bytes (you might need to cast from signed char)
source_sizenumber of bytes in the source buffer
Returns
0 on error, 1 on success (on error, mpg123_free_string is called on sb)

◆ mpg123_meta_check()

MPG123_EXPORT int mpg123_meta_check ( mpg123_handle mh)

Query if there is (new) meta info, be it ID3 or ICY (or something new in future).

Parameters
mhhandle
Returns
combination of flags, 0 on error (same as "nothing new")

◆ mpg123_meta_free()

MPG123_EXPORT void mpg123_meta_free ( mpg123_handle mh)

Clean up meta data storage (ID3v2 and ICY), freeing memory.

Parameters
mhhandle

◆ mpg123_id3()

MPG123_EXPORT int mpg123_id3 ( mpg123_handle mh,
mpg123_id3v1 **  v1,
mpg123_id3v2 **  v2 
)

Point v1 and v2 to existing data structures wich may change on any next read/decode function call. v1 and/or v2 can be set to NULL when there is no corresponding data.

Returns
MPG123_OK on success

◆ mpg123_id3_raw()

MPG123_EXPORT int mpg123_id3_raw ( mpg123_handle mh,
unsigned char **  v1,
size_t *  v1_size,
unsigned char **  v2,
size_t *  v2_size 
)

Return pointers to and size of stored raw ID3 data if storage has been configured with MPG123_RAW_ID3 and stream parsing passed the metadata already. Null value with zero size is a possibility! The storage can change at any next API call.

Parameters
v1address to store pointer to v1 tag
v1_sizesize of v1 data in bytes
v2address to store pointer to v2 tag
v2_sizesize of v2 data in bytes
Returns
MPG123_OK or MPG123_ERR. Only on MPG123_OK the output values are set.

◆ mpg123_icy()

MPG123_EXPORT int mpg123_icy ( mpg123_handle mh,
char **  icy_meta 
)

Point icy_meta to existing data structure wich may change on any next read/decode function call.

Parameters
mhhandle
icy_metareturn address for ICY meta string (set to NULL if nothing there)
Returns
MPG123_OK on success

◆ mpg123_icy2utf8()

MPG123_EXPORT char* mpg123_icy2utf8 ( const char *  icy_text)

Decode from windows-1252 (the encoding ICY metainfo used) to UTF-8. Note that this is very similar to mpg123_store_utf8(&sb, mpg123_text_icy, icy_text, strlen(icy_text+1)) .

Parameters
icy_textThe input data in ICY encoding
Returns
pointer to newly allocated buffer with UTF-8 data (You free() it!)
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