Creare un semplice Client di Jack con le risorse della libreria libjack
Da Gambas-it.org - Wikipedia.
JACK Audio Connection Kit è un server audio a bassa latenza sia per dati audio che per dati Midi. Jack consente di connettere svariate applicazioni client ad un dispositivo audio, ed anche con altri client. I Client di Jack possono funzionare sia come applicazioni con processi separati rispetto al server audio, sia come plugin all'interno dello stesso Jack.
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Creare un semplice Client di Jack con Gambas
Per creare in Gambas un semplice Client di Jack, e connettere le sue porte con il server Jack, bisognerà servirsi delle risorse offerte dalla libreria condivisa: "libjack.so.0.1.0 ".
Ogni porta audio in Jack è un canale audio mono in formato Single, quindi a 32-bit.
V'è da precisare che Jack in tal caso prevede una chiamata ad una routine callback, ma Gambas - almeno allo stato attuale - non è in grado di funzionare in un altro thread, causando così il crash dell'applicativo. Pertanto, bisognerà far funzionare la procedura di callback all'interno di una libreria C esterna da noi appositamente creata, che chiameremo ad esempio jk.c . Il codice sorgente di tale nostra apposita libreria dinamica condivisa potrà essere inserito nel codice Gambas; lì sarà prevista anche la riga di comando con Shell per compilare la libreria.
Creazione di un Client e connessione di tipo mono al server jack
Viene creato un Client di Jack, e vengono generate connessioni audio di tipo mono.
Private Const JackNullOption As Byte = 0
' Private Const JACK_DEFAULT_MIDI_TYPE As String = "8 bit raw midi"
Private Const JACK_DEFAULT_AUDIO_TYPE As String = "32 bit float mono audio"
Private Const JackPortIsInput As Byte = 1
Private Const JackPortIsOutput As Byte = 2
Private Const JackPortIsPhysical As Byte = 4
Private err As Integer
Private client As Pointer
Private input_port As Pointer
Private output_port As Pointer
Library "libjack:0.1.0"
' jack_client_t * jack_client_open (const char *client_name, jack_options_t options, jack_status_t *status,...)
' Open an external client session with a JACK server.
Private Extern jack_client_open(client_name As String, options As Integer, status As Pointer, server_name As String) As Pointer
' char * jack_get_client_name (jack_client_t *client)
' Returns a pointer to actual client name.
Private Extern jack_get_client_name(jack_client As Pointer) As String
' jack_nframes_t jack_get_sample_rate (jack_client_t *)
' Returns the sample rate of the jack system, as set by the user when jackd was started.
Private Extern jack_get_sample_rate(jack_client As Pointer) As Integer
' jack_port_t * jack_port_register (jack_client_t *client, const char *port_name, const char *port_type, unsigned long flags, unsigned long buffer_size)
' Create a new port for the client.
Private Extern jack_port_register(jack_client As Pointer, port_name As String, port_type As String, flags As Integer, buffer_size As Integer) As Pointer
' int jack_activate (jack_client_t *client)
' Tell the Jack server that the program is ready to start processing audio.
Private Extern jack_activate(jack_client As Pointer) As Integer
' const char ** jack_get_ports (jack_client_t *, const char *port_name_pattern, const char *type_name_pattern, unsigned long flags)
' Returns a NULL-terminated array of ports that match the specified arguments.
Private Extern jack_get_ports(jack_client As Pointer, port_name_pattern As String, type_name_pattern As String, flags As Integer) As Pointer
' const char * jack_port_name (const jack_port_t *port)
' Returns the full name of the jack_port_t (including the "client_name:" prefix).
Private Extern jack_port_name(jack_port As Pointer) As String
' int jack_connect (jack_client_t *, const char *source_port, const char *destination_port)
' Establish a connection between two ports.
Private Extern jack_connect(jack_client As Pointer, src_port As String, dest_port As String) As Integer
' int jack_client_close (jack_client_t *client)
' Disconnects an external client from a JACK server.
Private Extern jack_client_close(jack_client As Pointer) As Integer
' void Invoca_Callback (jack_client_t *cl, jack_port_t *it, jack_port_t *ot)
' Invoca la funzione principale della libreria ad hoc per la funzione "callback"
Private Extern Invoca_Callback(Pclient As Pointer, it As Pointer, ot As Pointer) As Integer In "/tmp/libjk"
Public Sub Form_Open()
' Invoca la sotto-procedura per salvare in apposto file .c il codice sorgente della nostra libreria "ad hoc" e per crearla:
CreaLibjk()
End
Public Sub Button1_Click()
Dim nomeClient As String = "Client_1"
Dim ports As Pointer
Dim sample As Integer
Dim porta, nome_porta As String
Dim status As Single
client = jack_client_open(nomeClient, JackNullOption, VarPtr(status), Null)
If IsNull(client) Then Print "Impossibile aprire una sessione del Client con il server Jack !"
nomeClient = jack_get_client_name(client)
Print "\nNome del Client = "; nomeClient
sample = jack_get_sample_rate(client)
Print "Campionamento = hz "; sample
Print "\n=========================================\n"
input_port = jack_port_register(client, "input_1", JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput, 0)
output_port = jack_port_register(client, "output_1", JACK_DEFAULT_AUDIO_TYPE, JackPortIsOutput, 0)
If (input_port = 0) Or (output_port = 0) Then Print "Nessuna porta di Jack disponibile !"
Invoca_Callback(client, input_port, output_port)
err = jack_activate(client)
If err <> 0 Then Print "Impossibile attivare il Client !"
' Connette le porte:
ports = jack_get_ports(client, "system:capture_1", Null, JackPortIsPhysical Or JackPortIsOutput)
If ports = 0 Then
Print "Impossibile agganciare alcuna porta fisica !"
Free(Object.Address(Button1))
Quit
Endif
porta = String@(Pointer@(ports))
nome_porta = jack_port_name(input_port)
Print porta, nome_porta
err = jack_connect(client, porta, nome_porta)
If err <> 0 Then Print "Impossibile connettere la porta d'Entrata !"
' Connette le porte:
ports = jack_get_ports(client, Null, Null, JackPortIsPhysical Or JackPortIsInput)
If ports = 0 Then Print "Impossibile agganciare alcuna porta fisica !"
porta = String@(Pointer@(ports))
nome_porta = jack_port_name(output_port)
Print nome_porta, porta
err = jack_connect(client, nome_porta, porta)
If err <> 0 Then Print "Impossibile connettere la porta d'Uscita !", err
Print
End
Private Procedure CreaLibjk() ' Salva il codice sorgente della nostra libreria dinamica .so, e poi la crea
File.Save("/tmp/jk.c", "#include <string.h>\n" &
"#include <jack/jack.h>" &
"\n\n" &
"jack_port_t *input_port;\n" &
"jack_port_t *output_port;\n" &
"jack_client_t *client;" &
"\n\n" &
"int process (jack_nframes_t, void *);" &
"\n\n" &
"void Invoca_Callback (jack_client_t *cl, jack_port_t *it, jack_port_t *ot) {\n" &
" client = cl;\n" &
" input_port = it;\n" &
" output_port = ot;\n\n" &
" jack_set_process_callback (client, process, 0);\n}" &
"\n\n" &
"int process (jack_nframes_t nframes, void *arg) {\n"
" jack_default_audio_sample_t *in, *out;\n" &
" in = jack_port_get_buffer (input_port, nframes);\n" &
" out = jack_port_get_buffer (output_port, nframes);\n\n" &
" memcpy (out, in, sizeof (jack_default_audio_sample_t) * nframes);\n\n" &
" return 0;\n}\n")
Shell "gcc -o /tmp/libjk.so /tmp/jk.c -shared -fPIC -ljack" Wait
End
Public Sub Button2_Click()
jack_client_close(client)
End
Creazione di un Client e connessione di tipo stereo al server jack
Vediamo ora un possibile codice per creare un Client ed effettuare una connessione di tipo stereo al server jack:
Private Const JackNullOption As Byte = 0
' Private Const JACK_DEFAULT_MIDI_TYPE As String = "8 bit raw midi"
Private Const JACK_DEFAULT_AUDIO_TYPE As String = "32 bit float mono audio"
Private Const JackPortIsInput As Byte = 1
Private Const JackPortIsOutput As Byte = 2
Private Const JackPortIsPhysical As Byte = 4
Private err As Integer
Private client As Pointer
Private porte_input As New Pointer[2]
Private porte_output As New Pointer[2]
Library "libjack:0.1.0"
' jack_client_t * jack_client_open (const char *client_name, jack_options_t options, jack_status_t *status,...)
' Open an external client session with a JACK server.
Private Extern jack_client_open(client_name As String, options As Integer, status As Pointer, server_name As String) As Pointer
' char * jack_get_client_name (jack_client_t *client)
' Returns a pointer to actual client name.
Private Extern jack_get_client_name(jack_client As Pointer) As String
' jack_nframes_t jack_get_sample_rate (jack_client_t *)
' Returns the sample rate of the jack system, as set by the user when jackd was started.
Private Extern jack_get_sample_rate(jack_client As Pointer) As Integer
' jack_port_t * jack_port_register (jack_client_t *client, const char *port_name, const char *port_type, unsigned long flags, unsigned long buffer_size)
' Create a new port for the client.
Private Extern jack_port_register(jack_client As Pointer, port_name As String, port_type As String, flags As Integer, buffer_size As Integer) As Pointer
' int jack_activate (jack_client_t *client)
' Tell the Jack server that the program is ready to start processing audio.
Private Extern jack_activate(jack_client As Pointer) As Integer
' const char ** jack_get_ports (jack_client_t *, const char *port_name_pattern, const char *type_name_pattern, unsigned long flags)
' Returns a NULL-terminated array of ports that match the specified arguments.
Private Extern jack_get_ports(jack_client As Pointer, port_name_pattern As String, type_name_pattern As String, flags As Integer) As Pointer
' const char * jack_port_name (const jack_port_t *port)
' Returns the full name of the jack_port_t (including the "client_name:" prefix).
Private Extern jack_port_name(jack_port As Pointer) As String
' int jack_connect (jack_client_t *, const char *source_port, const char *destination_port)
' Establish a connection between two ports.
Private Extern jack_connect(jack_client As Pointer, src_port As String, dest_port As String) As Integer
' int jack_client_close (jack_client_t *client)
' Disconnects an external client from a JACK server.
Private Extern jack_client_close(jack_client As Pointer) As Integer
' void Invoca_Callback (jack_client_t *cl, jack_port_t *it, jack_port_t *ot)
' Invoca la funzione principale della libreria ad hoc per la funzione "callback"
Private Extern Invoca_Callback(Pclient As Pointer, it As Pointer[], ot As Pointer[]) As Integer In "/tmp/libjk"
Public Sub Form_Open()
' Invoca la sotto-procedura per salvare in apposto file .c il codice sorgente della nostra libreria "ad hoc" e per crearla:
CreaLibjk()
End
Public Sub Button1_Click()
Dim nomeClient, nome_porta As String
Dim porte As Pointer
Dim b As Byte
Dim sample As Integer
Dim status As Single
nomeClient = "Client_1"
client = jack_client_open(nomeClient, JackNullOption, VarPtr(status), Null)
If IsNull(client) Then Print "Impossibile aprire una sessione del Client con il server Jack !"
nomeClient = jack_get_client_name(client)
Print "\nNome del Client = "; nomeClient
sample = jack_get_sample_rate(client)
Print "Campionamento = hz "; sample
Print "\n=========================================\n"
For b = 0 To 1
nome_porta = "input_" & CStr(b + 1)
porte_input[b] = jack_port_register(client, nome_porta, JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput, 0)
nome_porta = "output_" & CStr(b + 1)
porte_output[b] = jack_port_register(client, nome_porta, JACK_DEFAULT_AUDIO_TYPE, JackPortIsOutput, 0)
If (porte_input[b] = 0) Or (porte_output[b] = 0) Then Print "Nessuna porta di Jack disponibile !"
Next
Invoca_Callback(client, porte_input, porte_output)
err = jack_activate(client)
If err <> 0 Then Print "Impossibile attivare il Client !"
' '''''''''''''''''''''''''''''
Print "Connessione delle porte\n"
' Connette le porte:
porte = jack_get_ports(client, Null, Null, JackPortIsPhysical Or JackPortIsOutput)
nome_porta = String@(Pointer@(porte))
Print nome_porta, "--->", jack_port_name(porte_input[0])
Print String@(Pointer@(porte + SizeOf(gb.Pointer))), "--->", jack_port_name(porte_input[1])
Print
If porte = 0 Then
Print "Impossibile ottenere i nomi delle porte !"
Free(Object.Address(Button1))
Quit
Endif
For b = 0 To 1
err = jack_connect(client, String@(Pointer@(porte + (CInt(b) * SizeOf(gb.Pointer)))), jack_port_name(porte_input[b]))
If err <> 0 Then Print "Impossibile connettere le porte !"
Next
porte = jack_get_ports(client, Null, Null, JackPortIsPhysical Or JackPortIsInput)
nome_porta = String@(Pointer@(porte))
Print jack_port_name(porte_output[0]), "--->", nome_porta, nome_porta
Print jack_port_name(porte_output[1]), "--->", nome_porta, String@(Pointer@(porte + SizeOf(gb.Pointer)))
If porte = 0 Then
Print "Impossibile ottenere i nomi delle porte !"
Free(Object.Address(Button1))
Quit
Endif
For b = 0 To 1
err = jack_connect(client, jack_port_name(porte_output[b]), String@(Pointer@(porte + (CInt(b) * SizeOf(gb.Pointer)))))
If err <> 0 Then Print "Impossibile connettere le porte !"
Next
End
Private Procedure CreaLibjk() ' Salva il codice sorgente della nostra libreria dinamica .so, e poi la crea
File.Save("/tmp/jk.c", "#include <string.h>\n" &
"#include <jack/jack.h>" &
"\n\n" &
"jack_port_t **input_port;\n" &
"jack_port_t **output_port;\n" &
"jack_client_t *client;" &
"\n\n" &
"int process (jack_nframes_t, void *);" &
"\n\n" &
"int process (jack_nframes_t nframes, void *arg) {\n"
" int i;\n" &
" jack_default_audio_sample_t *in, *out;\n" &
" for (i = 0; i < 2; i++) {\n" &
" in = jack_port_get_buffer (input_port[i], nframes);\n" &
" out = jack_port_get_buffer (output_port[i], nframes);\n\n" &
" memcpy (out, in, sizeof (jack_default_audio_sample_t) * nframes);\n}\n\n" &
" return 0;\n}\n" &
"\n\n" &
"void Invoca_Callback (jack_client_t *cl, jack_port_t **it, jack_port_t **ot) {\n" &
" client = cl;\n" &
" input_port = it;\n" &
" output_port = ot;\n\n" &
" jack_set_process_callback (client, process, 0);\n}")
Shell "gcc -o /tmp/libjk.so /tmp/jk.c -shared -fPIC -ljack" Wait
End
Public Sub Button2_Click()
jack_client_close(client)
End
