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| (7 versioni intermedie di uno stesso utente non sono mostrate) |
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| − | '''LAME''' (''LAME Ain't an Mp3 Encoder'') è un codificatore MPEG Audio Layer III (mp3) di alta qualità rilasciato sotto licenza LGPL.
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| − | | + | #REDIRECT [[Convertire_un_file_WAV_in_formato_MP3_con_le_funzioni_esterne_del_API_di_Lame]] |
| − | =Convertire un file .wav in file mp3=
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| − | Con le risorse dell'[http://it.wikipedia.org/wiki/Application_programming_interface API] di LAME è possibile realizzare facilmente un semplice applicativo capace di convertire un file audio .wav in un file audio mp3.
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| − | Innanzitutto in Gambas dovremo dichiarare la [http://it.wikipedia.org/wiki/Dynamic-link_library libreria condivisa] .so, contenente le funzioni di ''LAME'', che attualmente è "''libmp3lame.so.0.0.0''":
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| − | Library "libmp3lame:0.0.0"
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| − | Ne mostriamo di seguito un esempio per la conversione di un file wav a 44100 hertz, 16bit, 2 canali:
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| − | Private Const PCM_SIZE As Short = 8192
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| − | Private Const MP3_SIZE As Short = 8192
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| − | Private Const vbr_default As Byte = 4
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| − | Library "libmp3lame:0.0.0"
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| − |
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| − | <FONT color=gray>' ''lame_global_flags lame_init()''
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| − | ' ''Initialize the encoder. sets default for all encoder parameters''</font>
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| − | Private Extern lame_init() As Pointer
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| − | <FONT color=gray>' ''int lame_set_in_samplerate(lame_global_flags flags, int rate)''
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| − | ' ''Input sample rate in Hz''</font>
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| − | Private Extern lame_set_in_samplerate(lame As Pointer, rate As Integer) As Integer
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| − | <FONT color=gray>' ''int lame_set_brate(lame_global_flags flags, int brate)''
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| − | ' ''Set one of bit-rate compression ratio.''</font>
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| − | Private Extern lame_set_brate(lame As Pointer, brate As Integer) As Integer
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| − | <FONT color=gray>' ''int lame_set_VBR(lame_global_flags flags, int vbr_mode)''
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| − | ' ''Types of VBR.''</font>
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| − | Private Extern lame_set_VBR(lame As Pointer, vbr As Integer) As Integer
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| − | <FONT color=gray>' ''int lame_init_params(lame_global_flags flags)''
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| − | ' ''Sets more internal configuration based On data provided above.returns - 1 If something failed.''</font>
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| − | Private Extern lame_init_params(lame As Pointer) As Integer
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| − | <FONT color=gray>' ''size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream)''
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| − | ' ''Legge da filStr nmemb elementi, ciascuno di dimensione size.''
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| − | ' ''Gli elementi letti vengono immagazzinati nel buffer puntato da ptr che deve essere di dimensioni adeguate.''
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| − | ' ''La funzione fread() ritorna il numero di elementi letti.''</font>
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| − | Private Extern fread(ptr As Pointer, size As Integer, nmemb As Integer, filStr As Pointer) As Integer In "libc:6"
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| − | <FONT color=gray>' ''int lame_encode_buffer_interleaved(lame_global_flags gfp, byte[] pcm, int num_samples, byte[] mp3buf, int mp3buf_size)''
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| − | ' ''This is a convenience method using byte[] array instead of short[], the byte[] buffer used must be 2x the length of the analogous short[] version.''
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| − | ' ''Input has L & R channel data interleaved. NOTE: num_samples = number of samples in the L (or R) channel, not the total number of samples in pcm[]''</font>
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| − | Private Extern lame_encode_buffer_interleaved(lame As Pointer, pcm As Pointer, num_samples As Integer, mp3buf As Pointer, mp3buf_size As Integer) As Integer
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| − | <FONT color=gray>' ''int lame_encode_flush(lame_global_flags gfp, unsigned char* mp3buf, Int size)''
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| − | ' ''lame_encode_flush will flush the intenal PCM buffers.''
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| − | ' ''"mp3buf" should be at least 7200 bytes long to hold all possible emitted data.''</font>
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| − | Private Extern lame_encode_flush(lame As Pointer, mp3buf As Pointer, size As Integer) As Integer
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| − | <FONT color=gray>' ''size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream)''
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| − | ' ''La funzione fwrite() scrive su filStr nmemb elementi, ciascuno di dimensione size.''
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| − | ' ''Il primo elemento e' individuato dal puntatore ptr. La funzione fwrite() ritorna il numero di elementi scritti.''</font>
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| − | Private Extern fwrite(ptr As Pointer, size As Integer, nmemb As Integer, filStr As Pointer) As Integer In "libc:6"
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| − | <FONT color=gray>' ''int lame_close(lame_global_flags flags)''
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| − | ' ''Final call to fFree all remaining buffers.''</font>
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| − | Private Extern lame_close(lame As Pointer) As Integer
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| − | <FONT color=gray>' ''FILE *fopen(const char *path, const char *mode)''
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| − | ' ''La funzione fopen() apre il file path associandolo ad uno stream.''</font>
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| − | Private Extern fopen(path As String, mode As String) As Pointer In "libc:6"
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| − | <FONT color=gray>' ''int fclose(FILE *stream)''
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| − | ' ''La funzione fclose() chiude il file associato a "stream" durante l'apertura con "fopen()".''</font>
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| − | Private Extern fclose(filStr As Pointer) As Integer In "libc:6"
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| − | '''Public''' Sub Main()
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| − | Dim letto, scritto As Integer
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| − | Dim pcm, mp3, handle, pcm_buffer, mp3_buffer As Pointer
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| − | pcm_buffer = Alloc(PCM_SIZE * 4)
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| − | mp3_buffer = Alloc(MP3_SIZE)
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| − | pcm = fopen("''percorso_del_file.wav''", "rb")
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| − | mp3 = fopen("''percorso_del_file.mp3''", "wb")
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| − | <FONT color=gray>' ''La libreria va innanzitutto inizializzata:''</font>
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| − | handle = lame_init()
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| − |
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| − | <FONT color=gray>' ''L'inizializzazione imposta i parametri con valori predefiniti.''
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| − | ' ''E' possibile modificare tali valori con apposite funzioni del tipo "lame_set_*()":''</font>
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| − | lame_set_in_samplerate(handle, 44100)
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| − | lame_set_brate(handle, 128)
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| − | lame_set_VBR(handle, vbr_default)
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| − | <FONT color=gray>' ''Dopo aver impostato i parametri, si controlla che tutto sia a posto mediante la funzione:''</font>
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| − | lame_init_params(handle)
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| − | Do
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| − | <FONT color=gray>' ''Si legge dal file .wav:''</font>
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| − | letto = fread(pcm_buffer, 2 * SizeOf(gb.Short), PCM_SIZE, pcm)
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| − | If letto = 0 Then
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| − | scritto = lame_encode_flush(handle, mp3_buffer, MP3_SIZE)
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| − | Else
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| − | scritto = lame_encode_buffer_interleaved(handle, pcm_buffer, letto, mp3_buffer, MP3_SIZE)
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| − | <FONT color=gray>' ''Si scrivono i dati codificati in mpeg nel file di destinazione:''</font>
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| − | fwrite(mp3_buffer, scritto, 1, mp3)
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| − | Endif
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| − | Loop While letto <> 0
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| − | <FONT color=gray>' ''Libera le due aree allocate; chiude l'handle della libreria e i due file:''</font>
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| − | Free(pcm_buffer)
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| − | Free(mp3_buffer)
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| − | lame_close(handle)
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| − | fclose(mp3)
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| − | fclose(pcm)
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| − | '''End'''
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| − | Nello stesso esempio potremo ridurre le funzioni a quelle sole strettamente appartenenti all'API di LAME:
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| − | Private Const vbr_default As Byte = 4
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| − | Library "libmp3lame:0.0.0"
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| − |
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| − | <FONT color=gray>' ''lame_global_flags lame_init()''</font>
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| − | Private Extern lame_init() As Pointer
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| − | <FONT color=gray>' ''int lame_set_in_samplerate(lame_global_flags flags, int rate)''</font>
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| − | Private Extern lame_set_in_samplerate(lame As Pointer, rate As Integer) As Integer
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| − |
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| − | <FONT color=gray>' ''int lame_set_brate(lame_global_flags flags, int brate)''</font>
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| − | Private Extern lame_set_brate(lame As Pointer, brate As Integer) As Integer
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| − |
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| − | <FONT color=gray>' ''int lame_set_VBR(lame_global_flags flags, int vbr_mode)''</font>
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| − | Private Extern lame_set_VBR(lame As Pointer, vbr As Integer) As Integer
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| − |
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| − | <FONT color=gray>' ''int lame_init_params(lame_global_flags flags)''</font>
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| − | Private Extern lame_init_params(lame As Pointer) As Integer
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| − |
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| − | <FONT color=gray>' ''int lame_encode_buffer_interleaved(lame_global_flags gfp, byte[] pcm, int num_samples, byte[] mp3buf, int mp3buf_size)''</font>
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| − | Private Extern lame_encode_buffer_interleaved(lame As Pointer, pcm As Byte[], num_samples As Integer, mp3buf As Byte[], mp3buf_size As Integer) As Integer
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| − | <FONT color=gray>' ''int lame_encode_flush(lame_global_flags gfp, unsigned char* mp3buf, Int size)''</font>
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| − | Private Extern lame_encode_flush(lame As Pointer, mp3buf As Byte[], size As Integer) As Integer
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| − | <FONT color=gray>' ''int lame_close(lame_global_flags flags)''</font>
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| − | Private Extern lame_close(lame As Pointer) As Integer
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| − | '''Public''' Sub Main()
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| − | Dim handle As Pointer
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| − | Dim pcm, mp3 As File
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| − | Dim percorsoFile As String = "''/percorso/del/file.wav''"
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| − | Dim scritto, campioni, dimensione As Integer
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| − | Dim pcm_buffer, mp3_buffer As Byte[]
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| − | pcm = Open percorsoFile For Read
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| − | mp3 = Open "''/percorso/del/nuovo/file.mp3''" For Create
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| − | dimensione = CInt(Stat(percorsoFile).Size)
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| − | mp3_buffer = New Byte[dimensione]
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| − | campioni = dimensione \ 4
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| − | <FONT color=gray>' ''Il decodificatore necessita di essere inizializzato:''</font>
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| − | handle = lame_init()
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| − |
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| − | <FONT color=gray>' ''L'inizializzazione imposta i parametri con valori predefiniti.''
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| − | ' ''E' possibile modificare tali valori con apposite funzioni del tipo "lame_set_*()":''</font>
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| − | lame_set_in_samplerate(handle, 44100)
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| − | lame_set_brate(handle, 128)
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| − | lame_set_VBR(handle, vbr_default)
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| − | <FONT color=gray>' ''Dopo aver impostato i parametri, si controlla che tutto sia a posto mediante la funzione:''</font>
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| − | lame_init_params(handle)
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| − | With pcm_buffer = New Byte[](Lof(pcm))
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| − | .Read(pcm, 0, Lof(pcm))
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| − | End With
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| − | scritto = lame_encode_buffer_interleaved(handle, pcm_buffer, campioni, mp3_buffer, dimensione)
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| − | mp3_buffer.Write(mp3, 0, scritto)
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| − | scritto = lame_encode_flush(handle, mp3_buffer, dimensione)
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| − | <FONT color=gray>' ''Chiude l'handle alla libreria e i due file:''</font>
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| − | lame_close(handle)
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| − | mp3.Close
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| − | pcm.Close
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| − | '''End'''
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| − | =Riferimenti=
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| − | * Il sito dell'[http://openinnowhere.sourceforge.net/lameonj/javadoc/lame/std/Lame.html#Lame%28%29 API di LAME]
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