Eseguire un file audio mediante le funzioni esterne del API di Allegro 5
Da Gambas-it.org - Wikipedia.
Allegro è una libreria utilizzata nella programmazione dei videogiochi e del multimediale.
La versione 5 della libreria Allegro consente di utilizzare le sue risorse anche in Gambas per l'esecuzione di file audio appartenenti ai seguenti formati: .wav, .flac, .ogg, .it, .mod, .s3m, .xm . [Nota 1]
Per poter fruire delle risorse della libreria di Allegro 5, è necessario installare e richiamare le librerie condivise: "liballegro.so.5.2.6 " e "liballegro_acodec.so.5.2.6 ".
Mostriamo un semplice ed essenziale esempio per poter eseguire un file audio:
Library "liballegro:5.2.6"
' uint32_t al_get_allegro_version (void)
' Returns the (compiled) version of the Allegro library.
Private Extern al_get_allegro_version() As Integer
' bool al_install_system (int version, int (*atexit_ptr)(void (*)(void)))
' Initialize the Allegro system.
Private Extern al_install_system(version As Integer, atexit_ptr As Pointer) As Boolean
' void al_uninstall_system (void)
' Closes down the Allegro system.
Private Extern al_uninstall_system()
Library "liballegro_acodec:5.2.6"
Private Const ALLEGRO_PLAYMODE_ONCE As Integer = 256
' bool al_install_audio (void)
' Install the audio subsystem.
Private Extern al_install_audio() As Boolean
' bool al_init_acodec_addon (void)
' Registers all the known audio file type handlers for al_load_sample.
Private Extern al_init_acodec_addon() As Boolean
' bool al_reserve_samples (int reserve_samples)
' Reserves a number of sample instances, attaching them to the default mixer.
Private Extern al_reserve_samples(reserve_samples As Integer) As Boolean
' ALLEGRO_SAMPLE * al_load_sample (const char *filename)
' Loads a few different audio file formats based on their extension.
Private Extern al_load_sample(filename As String) As Pointer
' unsigned int al_get_sample_frequency (const ALLEGRO_SAMPLE *spl)
' Return the frequency of the sample.
Private Extern al_get_sample_frequency(spl As Pointer) As Integer
' ALLEGRO_AUDIO_DEPTH al_get_sample_depth (const ALLEGRO_SAMPLE *spl)
' Return the audio depth.
Private Extern al_get_sample_depth(spl As Pointer) As Integer
' unsigned int al_get_sample_length (const ALLEGRO_SAMPLE *spl)
' Return the length of the sample in sample values.
Private Extern al_get_sample_length(spl As Pointer) As Integer
' ALLEGRO_CHANNEL_CONF al_get_sample_channels (const ALLEGRO_SAMPLE *spl)
' Return the channel configuration.
Private Extern al_get_sample_channels(spl As Pointer) As Integer
' bool al_play_sample (ALLEGRO_SAMPLE *data, float gain, float pan, float speed, ALLEGRO_PLAYMODE loop, ALLEGRO_SAMPLE_ID *ret_id)
' Plays a sample on one of the sample instances created by al_reserve_samples.
Private Extern al_play_sample(data As Pointer, gain As Single, pan As Single, speed As Single, playmode As Integer, ret_id As Pointer) As Boolean
' void al_rest (double seconds)
' Waits for the specified number seconds.
Private Extern al_rest(seconds As Float)
' void al_destroy_sample (ALLEGRO_SAMPLE *spl)
' Free the sample data structure.
Private Extern al_destroy_sample(spl As Pointer)
Public Sub Main()
Dim file_audio As String
Dim audio As Pointer
Dim frequenza, pos As Integer
If al_install_system(al_get_allegro_version(), 0) = False Then Error.Raise("Impossibile inizializzare la libreria Allegro 5 !")
If al_install_audio() = False Then Error.Raise("Impossibile inizializzare l'audio !")
If al_init_acodec_addon() = False Then Error.Raise("Impossibile inizializzare le codifiche audio !")
If al_reserve_samples(1) = False Then Error.Raise("Impossibile riservare un numero di campioni audio !")
file_audio = "/percorso/del/file/audio"
audio = al_load_sample(file_audio)
If audio == 0 Then Error.Raise("File audio non caricato !")
Print "File audio: "; file_audio
frequenza = al_get_sample_frequency(audio)
Print "Frequenza di campionamento: "; frequenza; " Hertz"
Print "Risoluzione campionamento: "; IIf(al_get_sample_depth(audio) = 1, "16", "8"); "-bit"
Print "Numero dei canali audio: "; al_get_sample_channels(audio) \ 16
pos = al_get_sample_length(audio)
Print "Durata dell'audio: "; Time(0, 0, 0, CSingle(pos / frequenza) * 1000)
' Esegue il file audio:
al_play_sample(audio, 1.0, 0.0, 1.0, ALLEGRO_PLAYMODE_ONCE, 0)
' Consente l'esecuzione per l'intera durata del file:
al_rest(CFloat(pos / frequenza))
' Va in chiusura:
al_destroy_sample(audio)
al_uninstall_system()
End
Mostrare il tempo trascorso
Se si vuol far mostrare il tempo trascorso dall'inizio dell'esecuzione del file audio, allora il precedente codice potrà essere così modificato:
Library "liballegro:5.2.6"
' uint32_t al_get_allegro_version (void)
' Returns the (compiled) version of the Allegro library.
Private Extern al_get_allegro_version() As Integer
' bool al_install_system (int version, int (*atexit_ptr)(void (*)(void)))
' Initialize the Allegro system.
Private Extern al_install_system(version As Integer, atexit_ptr As Pointer) As Boolean
' void al_uninstall_system (void)
' Closes down the Allegro system.
Private Extern al_uninstall_system()
Library "liballegro_acodec:5.2.6"
Private Const ALLEGRO_PLAYMODE_ONCE As Integer = 256
' bool al_install_audio (void)
' Install the audio subsystem.
Private Extern al_install_audio() As Boolean
' bool al_init_acodec_addon (void)
' Registers all the known audio file type handlers for al_load_sample.
Private Extern al_init_acodec_addon() As Boolean
' bool al_reserve_samples (int reserve_samples)
' Reserves a number of sample instances, attaching them to the default mixer.
Private Extern al_reserve_samples(reserve_samples As Integer) As Boolean
' ALLEGRO_SAMPLE * al_load_sample (const char *filename)
' Loads a few different audio file formats based on their extension.
Private Extern al_load_sample(filename As String) As Pointer
' unsigned int al_get_sample_frequency (const ALLEGRO_SAMPLE *spl)
' Return the frequency of the sample.
Private Extern al_get_sample_frequency(spl As Pointer) As Integer
' ALLEGRO_AUDIO_DEPTH al_get_sample_depth (const ALLEGRO_SAMPLE *spl)
' Return the audio depth.
Private Extern al_get_sample_depth(spl As Pointer) As Integer
' unsigned int al_get_sample_length (const ALLEGRO_SAMPLE *spl)
' Return the length of the sample in sample values.
Private Extern al_get_sample_length(spl As Pointer) As Integer
' ALLEGRO_CHANNEL_CONF al_get_sample_channels (const ALLEGRO_SAMPLE *spl)
' Return the channel configuration.
Private Extern al_get_sample_channels(spl As Pointer) As Integer
' bool al_play_sample (ALLEGRO_SAMPLE *data, float gain, float pan, float speed, ALLEGRO_PLAYMODE loop, ALLEGRO_SAMPLE_ID *ret_id)
' Plays a sample on one of the sample instances created by al_reserve_samples.
Private Extern al_play_sample(data As Pointer, gain As Single, pan As Single, speed As Single, playmode As Integer, ret_id As Pointer) As Boolean
' void al_rest (double seconds)
' Waits for the specified number seconds.
Private Extern al_rest(seconds As Float)
' void al_destroy_sample (ALLEGRO_SAMPLE *spl)
' Free the sample data structure.
Private Extern al_destroy_sample(spl As Pointer)
Public Sub Main()
Dim file_audio As String
Dim audio As Pointer
Dim frequenza, pos As Integer
Dim tempus As Date
If al_install_system(al_get_allegro_version(), 0) = False Then Error.Raise("Impossibile inizializzare la libreria Allegro 5 !")
If al_install_audio() = False Then Error.Raise("Impossibile inizializzare l'audio !")
If al_init_acodec_addon() = False Then Error.Raise("Impossibile inizializzare le codifiche audio !")
If al_reserve_samples(1) = False Then Error.Raise("Impossibile riservare un numero di campioni audio !")
file_audio = "/percorso/del/file/audio"
audio = al_load_sample(file_audio)
If audio == 0 Then Error.Raise("File audio non caricato !")
Print "File audio: "; file_audio
frequenza = al_get_sample_frequency(audio)
Print "Frequenza di campionamento: "; frequenza; " Hertz"
Print "Risoluzione campionamento: "; IIf(al_get_sample_depth(audio) = 1, "16", "8"); "-bit"
Print "Numero dei canali audio: "; al_get_sample_channels(audio) \ 16
pos = al_get_sample_length(audio)
Print "Durata dell'audio: "; Time(0, 0, 0, CSingle(pos / frequenza) * 1000)
' Esegue il file audio:
al_play_sample(audio, 1.0, 0.0, 1.0, ALLEGRO_PLAYMODE_ONCE, 0)
' Consente l'esecuzione per l'intera durata del file e mostra il tempo trascorso dall'inizio dell'esecuzione del file audio:
tempus = Time(Now)
Print
While CFloat(DateDiff(tempus, Time(Now), gb.Millisecond)) < CFloat(pos / frequenza) * 1000
Write "\rTempo trascorso: " & Time(0, 0, 0, DateDiff(tempus, Time(Now), gb.Millisecond))
Wait 0.01
Wend
' Va in chiusura:
al_destroy_sample(audio)
al_uninstall_system()
End
Note
[1] La versione 5 della libreria Allegro non consente di eseguire file Midi; funzionalità posseduta, invece, dalla precedente versione 4, ancora utilizzabile, ma solo in sostituzione della 5.
