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"

' DiscId *discid_new()
' Return a handle for a new DiscId object.
Private Extern discid_new() As Pointer

' 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.
Private Extern discid_read_sparse(d As Pointer, device As String, features As Integer) As Integer

' char *discid_get_error_msg(DiscId *d)
' Return a human-readable error message.
Private Extern discid_get_error_msg(d As Pointer) As String

' char *discid_get_id(DiscId *d)
' Return a MusicBrainz DiscID.
Private Extern discid_get_id(d As Pointer) As String

' char *discid_get_freedb_id(DiscId *d)
' Return a FreeDB DiscID.
Private Extern discid_get_freedb_id(d As Pointer) As String

' int discid_get_first_track_num(DiscId *d)
' Return the number of the first track on this disc.
Private Extern discid_get_first_track_num(d As Pointer) As Integer

' int discid_get_last_track_num(DiscId *d)
' Return the number of the last audio track on this disc.
Private Extern discid_get_last_track_num(d As Pointer) As Integer

' int discid_get_sectors(DiscId *d)
' Return the length of the disc in sectors.
Private Extern discid_get_sectors(d As Pointer) As Integer

' int discid_get_track_length(DiscId *d, int track_num)
' Return the length of a track in sectors.
Private Extern discid_get_track_length(d As Pointer, track_num As Integer) As Integer

' int discid_get_track_offset(DiscId *d, int track_num)
' Return the sector offset of a track.
Private Extern discid_get_track_offset(d As Pointer, track_num As Integer) As Integer

' void discid_free(DiscId *d)
' Release the memory allocated for the DiscId object.
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