Visualizza wikitesto di Convertire un file OggVorbis in WAV ed estrarne anche informazioni con le funzioni esterne del API di VorbisFile

La libreria di '''''VorbisFile''''' consente di estrarre informazioni di carattere generale da un file audio ''OggVorbis'' e di convertirlo in un file audio WAV.

Per poter fruire in Gambas delle risorse del API di ''Ogg Vorbis'' si dovrà utilizzare la libreria condivisa: "''libvorbisfile.so.3.3.8'' ".

Di seguito mostreremo un semplice codice per convertire un file ''OggVorbis'' (44100 hertz, 16 bit, 2 canali) nel corrispondente file ''WAV''.
 Library "libvorbisfile:3.3.8"
 
 Public Struct vorbis_comment
   user_comments As Pointer
   comment_lengths As Pointer
   comments As Integer
   vendor As Pointer
 End Struct
 
 Public Struct ogg_sync_state
   data As Pointer
   storage As Integer
   fill As Integer
   returned As Integer
   unisynced As Integer
   headerbytes As Integer
   bodybytes As Integer
 End Struct
 
 Public Struct ogg_stream_state
   body_data As Pointer
   body_storage As Long
   body_fill As Long
   body_returned As Long
   lacing_vals As Pointer
   granule_vals As Pointer
   lacing_storage As Long
   lacing_fill As Long
   lacing_packet As Long
   lacing_returned As Long
   header[282] As Byte
   header_fill As Integer
   e_o_s As Integer
   b_o_s As Integer
   serialno As Long
   pageno As Long
   packetno As Long
   granulepos As Long
 End Struct
 
 Public Struct vorbis_dsp_state
   analysisp As Integer
   vi As Pointer
   pcm As Pointer
   pcmret As Pointer
   pcm_storage As Integer
   pcm_current As Integer
   pcm_returned As Integer
   preextrapolate As Integer
   eofflag As Integer
   lW As Long
   W As Long
   nW As Long
   centerW As Long
   granulepos As Long
   sequence As Long
   glue_bits As Long
   time_bits As Long
   floor_bits As Long
   res_bits As Long
 End Struct
 
 Public Struct oggpack_buffer
   endbyte As Long
   endbit As Integer
   buffer As Pointer
   ptr As Pointer
   storage As Long
 End Struct
 
 Public Struct vorbis_block
   pcm As Pointer
   opb As Struct Oggpack_buffer
   lW As Long
   W As Long
   nW As Long
   pcmend As Integer
   mode As Integer
   eofflag As Integer
   granulepos As Long
   sequence As Long
   vd As Pointer
   localstore As Pointer
   localtop As Long
   localalloc As Long
   totaluse As Long
   reap As Pointer
   glue_bits As Long
   time_bits As Long
   floor_bits As Long
   res_bits As Long
   internal As Pointer
 End Struct
 
 Public Struct ov_callbacks
   fread As Pointer
   _ov_header_fseek_wrap As Pointer
   void As Pointer
   ftell As Pointer
 End Struct
 
 Public Struct OggVorbis_File
   datasource As Pointer
   seekable As Integer
   offset As Long
   end_ As Long
   oy As Struct Ogg_sync_state
   links As Integer
   offsets As Pointer
   dataoffsets As Pointer
   serialnos As Pointer
   pcmlengths As Pointer
   vi As Pointer
   vc As Pointer
   pcm_offset As Long
   ready_state As Integer
   current_serialno As Long
   current_link As Integer
   bittrack As Float
   samptrack As Float
   os As Struct Ogg_stream_state
   vd As Struct Vorbis_dsp_state
   vb As Struct Vorbis_block
   callbacks As Struct Ov_callbacks
 End Struct
 
 Public Struct vorbis_info
   version As Integer
   channels As Integer
   rate As Long
   bitrate_upper As Long
   bitrate_nominal As Long
   bitrate_lower As Long
   bitrate_window As Long
 End Struct
  
 <FONT color=gray>' ''int ov_fopen(const char *path,OggVorbis_File *vf)''
 ' ''Opens and initialize an OggVorbis_File structure.''</font>
 Private Extern ov_fopen(path As String, vf As OggVorbis_File) As Integer
  
 <FONT color=gray>' ''ogg_int64_t ov_pcm_total(OggVorbis_File *vf,int i)''
 ' ''Returns the total pcm samples of the physical bitstream or a specified logical bitstream.''</font>
 Private Extern ov_pcm_total(vf As OggVorbis_File, i As Integer) As Long
 
 <FONT color=gray>' ''vorbis_info *ov_info(OggVorbis_File *vf,int link)''
 ' ''Returns the vorbis_info struct for the specified bitstream.''</font>
 Private Extern ov_info(vf As OggVorbis_File, linkI As Integer) As Vorbis_info
   
 <FONT color=gray>' ''double ov_time_total(OggVorbis_File *vf,int i)''
 ' ''Returns the total time in seconds of the physical bitstream or a specified logical bitstream.''</font>
 Private Extern ov_time_total(vf As OggVorbis_File, i As Integer) As Float
 
 <FONT color=gray>' ''vorbis_comment *ov_comment(OggVorbis_File *vf,int link)''
 ' ''Returns a pointer to the vorbis_comment struct for the specified bitstream.''</font>
 Private Extern ov_comment(vf As OggVorbis_File, lnk As Integer) As Pointer
 
 <FONT color=gray>' ''long ov_read(OggVorbis_File *vf, char *buffer, int length, int bigendianp, int word, int sgned, int *bitstream)''
 ' ''Decode a Vorbis file within a loop.''</font>
 Private Extern ov_read(vf As OggVorbis_File, buffer As Pointer, length As Integer, bigendianp As Integer, word As Integer, sgned As Integer, bitstream As Pointer) As Long
   
 
 '''Public''' Sub Main()
  
  Dim vf As New OggVorbis_File
  Dim vi As Vorbis_info
  Dim commenti As Vorbis_comment
  Dim fin As Pointer
  Dim eo, current_section, err, i As Integer
  Dim rit As Long
  Dim datiPCMgrezzi, fileOGG As String
  Dim pcmout As New Byte[](4096)
  Dim fl As File
  Dim b As Byte
   
  fileOGG = "<FONT color=gray>''/percorso/del/file.ogg''</font>"
  datiPCMgrezzi = Temp
    
  fl = Open datiPCMgrezzi For Create
     
  err = ov_fopen(fileOGG, vf)
  If err < 0 Then Error.Raise("Il file caricato potrebbe non essere del formato Ogg !")
   
 <FONT color=gray>' ''Estrae alcune informazioni generali del file audio Ogg caricato:''</font>
  vi = ov_info(vf, -1)
  
  Print "File audio:                              "; fileOGG
  With vi
    Print "Frequenza di campionamento:              "; .rate; " Hertz"
    Print "Canali di uscita:                        "; .channels
    Print "Bitrate:                                 "; .bitrate_nominal \ 1000; " Kbps"
    Print "Durata del file ogg:                     "; Time(0, 0, 0, ov_time_total(vf, -1) * 1000)
    Print "Lunghezza dei campioni decodificati:     "; ov_pcm_total(vf, -1); " byte"
  End With
  Print "Commenti presenti nel file ogg:"
  With commenti = ov_comment(vf, -1)
    If commenti.comments > 0 Then
      For b = 0 To commenti.comments - 1
        i = 8 * b
        Print "   "; String@(Pointer@(commenti.user_comments + i))
      Next
      Print "   "; String@(commenti.vendor)
    Endif 
  End With
 
  Write "\e[5mAttendere...\e[0m"
  Flush
 
 <FONT color=gray>' ''Ciclo per la decodifica dei dati Ogg e per la scrittura del file contenente i dati grezzi PCM:''</font>
  While eo = 0
    rit = ov_read(vf, pcmout.Data, pcmout.Count, 0, 2, 1, VarPtr(current_section))
    If rit = 0 Then
      eo = 1
    Else
 <FONT color=gray>' ''Scrive il file contenente i dati grezzi PCM:''</font>
      pcmout.Write(fl, 0, rit)
    Endif
  Wend
 
  Write "\rConversione terminata !"
 
 <FONT color=gray>' ''Va a creare il file WAV finale:''</font>
  crea_file_wav(datiPCMgrezzi)
 
 <FONT color=gray>' ''Va in chiusura:''</font>
  fl.Close
 
 '''End'''
 
 '''Private''' Procedure crea_file_wav(datiGrezzi As String)
  
  Dim fl, fwav As File
  Dim i, i2 As Integer
  Dim dati As New Byte[](Stat(datiGrezzi).Size)
  Dim bh As Byte[] = [&52, &49, &46, &46, &00, &00, &00, &00, &57, &41, &56, &45, &66, &6D, &74, &20, &10, &00, &00, &00, &01, &00, &02, &00,
                     &44, &AC, &00, &00, &10, &B1, &02, &00, &04, &00, &10, &00, &64, &61, &74, &61, &00, &00, &00, &00]    <FONT color=gray>' ''blocco d'intestazione del file wav futuro: 2 canali, 16 bit, hz 44100''</font>
                     
  fl = Open datiGrezzi For Read
  dati.Read(fl)
      
  i = Lof(fl)
  fl.Close
  i2 = i + 36
  
 <FONT color=gray>' ''Imposta il valore dimensionale di 4 byte a partire dal 5° byte del futuro file wav:''</font>
  bh[4] = i2 And &FF
  bh[5] = Shr(i2 And &FF00&, 8)
  bh[6] = Shr(i2 And &FF0000&, 16)
  bh[7] = Shr(i2 And &FF000000&, 24)
  
 <FONT color=gray>' ''Imposta il valore dimensionale di 4 byte a partire dal 41° byte del futuro file wav.''
 ' ''Esso è relativo alla quantità effettiva dei dati audio grezzi.''</font>
  bh[40] = i And &FF
  bh[41] = Shr(i And &FF00&, 8)
  bh[42] = Shr(i And &FF0000&, 16)
  bh[43] = Shr(i And &FF000000&, 24)
      
  bh.Insert(dati, 44)
 
  fwav = Open "<FONT color=gray>''/percorso/del/file.wav''</font>" For Create
 
 <FONT color=gray>' ''Inizia la scrittura del file wav:''</font>
  bh.Write(fwav, 0, bh.Count)
   
  Print "\n\nDurata del file WAV: "; Time(0, 0, 0, ((i * 8) / (44100 * 16 * 2)) * 1000)
    
  dati.Clear
  bh.Clear
  fl.Close
  fwav.Close
  
 '''End'''



=Riferimenti=
* http://www.xiph.org/vorbis/doc/
* http://www.vorbis.com/setup_linux/