Visualizza wikitesto di Convertire un numero di settori di un CD/DVD in ore,minuti,secondi con le funzioni del API Libdiscid

'''Libdiscid''' è una libreria C per la creazione di un Id disco ''MusicBrainz'' e freedb da un CD audio. Essa legge una tabella di contenuti di un CD (TOC) e genera un identificatore che può essere utilizzato per cercare il CD in ''MusicBrainz''.

Per fruire delle sue risorse in Gambas, è necessario installare richiamare la libreria condivisa: "''libdiscid.so.0.6.1''"


Mostriamo un semplice esempio per convertire un numero di settori di un CD/DVD in ore:minuti:secondi:
 Private Const SETTORI_PER_SECONDO As Integer = 75
 
 Library "libdiscid:0.6.1"
 
 <FONT Color=gray>' ''DiscId *discid_new()''
 ' ''Return a handle for a new DiscId object.''</font>
 Private Extern discid_new() As Pointer
 
 <FONT Color=gray>' ''int discid_read_sparse(DiscId *d, const char *device, unsigned int features)''
 ' ''Read the disc in the given CD-ROM/DVD-ROM drive extracting only the TOC and additionally specified features.''</font>
 Private Extern discid_read_sparse(d As Pointer, device As String, features As Integer) As Integer
 
 <FONT Color=gray>' ''char *discid_get_error_msg(DiscId *d)''
 ' ''Return a human-readable error message.''</font>
 Private Extern discid_get_error_msg(d As Pointer) As String
 
 <FONT Color=gray>' ''char *discid_get_id(DiscId *d)''
 ' ''Return a MusicBrainz DiscID.''</font>
 Private Extern discid_get_id(d As Pointer) As String
 
 <FONT Color=gray>' ''char *discid_get_freedb_id(DiscId *d)''
 ' ''Return a FreeDB DiscID.''</font>
 Private Extern discid_get_freedb_id(d As Pointer) As String
 
 <FONT Color=gray>' ''int discid_get_first_track_num(DiscId *d)''
 ' ''Return the number of the first track on this disc.''</font>
 Private Extern discid_get_first_track_num(d As Pointer) As Integer
 
 <FONT Color=gray>' ''int discid_get_last_track_num(DiscId *d)''
 ' ''Return the number of the last audio track on this disc.''</font>
 Private Extern discid_get_last_track_num(d As Pointer) As Integer
 
 <FONT Color=gray>' ''int discid_get_sectors(DiscId *d)''
 ' ''Return the length of the disc in sectors.''</font>
 Private Extern discid_get_sectors(d As Pointer) As Integer
 
 <FONT Color=gray>' ''int discid_get_track_length(DiscId *d, int track_num)''
 ' ''Return the length of a track in sectors.''</font>
 Private Extern discid_get_track_length(d As Pointer, track_num As Integer) As Integer
 
 <FONT Color=gray>' ''int discid_get_track_offset(DiscId *d, int track_num)''
 ' ''Return the sector offset of a track.''</font>
 Private Extern discid_get_track_offset(d As Pointer, track_num As Integer) As Integer
 
 <FONT Color=gray>' ''void discid_free(DiscId *d)''
 ' ''Release the memory allocated for the DiscId object.''</font>
 Private Extern discid_free(d As Pointer)
 
 
 '''Public''' Sub Main()
 
  Dim disc, dev As Pointer
  Dim err, prima_traccia, ultima_traccia As Integer
  Dim settori, i As Integer
  Dim durata_in_secondi As Single
 
   disc = discid_new()
    
   err = discid_read_sparse(disc, Null, 0)
   If err = 0 Then Error.Raise("Errore: " & discid_get_error_msg(disc))
    
   Print "ID Disco: "; Null, discid_get_id(disc)
   Print "FreeDB DiscID: "; Null, discid_get_freedb_id(disc)
    
   prima_traccia = discid_get_first_track_num(disc)
   Print "Prima traccia: "; Null, prima_traccia
   ultima_traccia = discid_get_last_track_num(disc)
   Print "Ultima traccia: "; Null; ultima_traccia
    
   settori = discid_get_sectors(disc)
   durata_in_secondi = settori / SETTORI_PER_SECONDO
   Print "Lunghezza: "; Null, settori; " Settori   ("; CStr(Date(0, 0, 0, 0, 0, 0, durata_in_secondi * 1000)); ")"
   Print
   For i = prima_traccia To ultima_traccia
     settori = discid_get_track_length(disc, i)
     Durata_Settori(disc, settori, i)
   Next
 
   discid_free(disc)
 
 '''End'''
 
 
 '''Private''' Procedure Durata_Settori(ds As Pointer, sett As Integer, c As Integer)
 
  Dim durata_in_secondi As Single
  
   durata_in_secondi = sett / SETTORI_PER_SECONDO
   
   Print "Traccia "; c; ":"; Null, discid_get_track_offset(ds, c); Null, sett, " ("; CStr(Date(0, 0, 0, 0, 0, 0, durata_in_secondi * 1000)); ")"
 
 '''End'''




=Riferimenti=
* http://musicbrainz.org/doc/libdiscid