Conoscere con le funzioni esterne di PortAudio i dispositivi audio presenti nel sistema
Da Gambas-it.org - Wikipedia.
Versione del 9 lug 2014 alle 16:19 di Vuott (Discussione | contributi)
La libreria PortAudio è una libreria per la gestione in tempo reale dei dati audio in entrata ed in uscita. Essa fa parte di un assortimento di API e librerie create per la musica e per altri media.
E' possibile con alcune funzioni esterne della libreria PortAudio conoscere i dispositivi audio presenti nel proprio sistema. Sarà necessario avere installata nel proprio sistema la libreria condivisa: libportaudio.so.2.0.0
Mostriamo di seguito un possibile codice:
Public Struct PaDeviceInfo
structVersion As Integer
name As Pointer
hostApi As Integer
maxInputChannels As Integer
maxOutputChannels As Integer
defaultLowInputLatency As Float
defaultLowOutputLatency As Float
defaultHighInputLatency As Float
defaultHighOutputLatency As Float
defaultSampleRate As Float
End Struct
Public Struct PaStreamParameters
device As Integer
channelCount As Integer
sampleFormat As Long
suggestedLatency As Float
hostApiSpecificStreamInfo As Pointer
End Struct
Library "libportaudio:2.0.0"
Private Const paNoError As Integer = 0
Private Const paInt16 As Long = 8
Private Const paFormatIsSupported As Integer = 0
' PaError Pa_Initialize(void)
' Library initialization function - call this before using PortAudio.
' This function initializes internal data structures and prepares underlying host APIs for use.
Private Extern Pa_Initialize() As Integer
' PaDeviceIndex Pa_GetDeviceCount(void)
' Retrieve the number of available devices. The number of available devices may be zero.
Private Extern Pa_GetDeviceCount() As Integer
' const PaDeviceInfo * Pa_GetDeviceInfo(PaDeviceIndex device)
' Retrieve a pointer to a PaDeviceInfo structure containing information about the specified device.
Private Extern Pa_GetDeviceInfo(device As Integer) As PaDeviceInfo
' PaDeviceIndex Pa_GetDefaultInputDevice(void)
' Retrieve the index of the default input device.
Private Extern Pa_GetDefaultInputDevice() As Integer
' PaDeviceIndex Pa_GetDefaultOutputDevice(void)
' Retrieve the index of the default output device.
Private Extern Pa_GetDefaultOutputDevice() As Integer
' PaError Pa_IsFormatSupported(const PaStreamParameters *inputParameters, const PaStreamParameters *outputParameters, double sampleRate)
' Determine whether it would be possible to open a stream with the specified parameters.
Private Extern Pa_IsFormatSupported(ip As PaStreamParameters, op As PaStreamParameters, sampleRate As Float) As Integer
' PaError Pa_Terminate(void)
' Library termination function - call this when finished using PortAudio.
Private Extern Pa_Terminate() As Integer
' const char *Pa_GetErrorText(PaError errnum)
' Translates the supplied PortAudio error number into a human readable message.
Private Extern Pa_GetErrorText(errnum As Integer) As String
Public Sub Main()
Dim err, i, j, numDevices As Integer
Dim pdi As New PaDeviceInfo
Dim INparametri, EXparametri As New PaStreamParameters
Dim defI, defO, ag1, ag2 As String
err = Pa_Initialize()
If err < 0 Then Error.Raise("Impossibile inizializzare la libreria 'PortAudio': " & Pa_GetErrorText(err))
numDevices = Pa_GetDeviceCount()
If numDevices < 0 Then Error.Raise("Impossibile rilevare la presenza di dispositivi audio: " & Pa_GetErrorText(err))
Print "Numbero di dispositivi = "; numDevices
For i = 0 To numDevices - 1
defI = Null
defO = Null
ag1 = Null
ag2 = Null
pdi = Pa_GetDeviceInfo(i)
Print "\n--------------------------------------- dispositivo #"; i
j = 0
If i = Pa_GetDefaultInputDevice() Then
defI = "\n[ Default Input"
j = 1
Endif
If i = Pa_GetDefaultOutputDevice() Then
If j Then
ag1 = ","
Else
ag1 = "["
Endif
defO = " Default Output"
j = 1
Endif
If j = 1 Then ag2 = " ]"
Print defI; ag1; defO; ag2
' Scrive i campi relativi alle informazioni di ciascun dispositivo audio rilevato:
Print "Nome = "; String@(pdi.name)
Print "Max Entrate = "; pdi.maxInputChannels, ", Max Uscite = "; pdi.maxOutputChannels
Print "Default low input latency = "; pdi.defaultLowInputLatency
Print "Default low output latency = "; pdi.defaultLowOutputLatency
Print "Default high input latency = "; pdi.defaultHighInputLatency
Print "Default high output latency = "; pdi.defaultHighOutputLatency
Print "Default sample rate = ", pdi.defaultSampleRate
INparametri.device = i
INparametri.channelCount = pdi.maxInputChannels
INparametri.sampleFormat = paInt16
INparametri.suggestedLatency = 0
INparametri.hostApiSpecificStreamInfo = 0
EXparametri.device = i
EXparametri.channelCount = pdi.maxOutputChannels
EXparametri.sampleFormat = paInt16
EXparametri.suggestedLatency = 0
EXparametri.hostApiSpecificStreamInfo = 0
If INparametri.channelCount > 0 Then
Print "Supported standard sample rates\n for half-duplex 16 bit "; INparametri.channelCount; "channel input = "
FrequenzeCampionamentoSupportate(INparametri, Null)
Endif
If EXparametri.channelCount > 0 Then
Print "Supported standard sample rates\n for half-duplex 16 bit "; EXparametri.channelCount; "channel input = "
FrequenzeCampionamentoSupportate(Null, EXparametri)
Endif
If (INparametri.channelCount > 0) And (EXparametri.channelCount > 0) Then
Print "Supported standard sample rates\n for full-duplex 16 bit "; INparametri.channelCount; "channel Input , "; EXparametri.channelCount; " channel Output = "
FrequenzeCampionamentoSupportate(INparametri, EXparametri)
Endif
Next
' Va in chiusura:
Pa_Terminate()
End
Private Procedure FrequenzeCampionamentoSupportate(inputParameters As PaStreamParameters, outputParameters As PaStreamParameters)
Dim standardSampleRates As Float[] = [8000.0, 9600.0, 11025.0, 12000.0, 16000.0, 22050.0, 24000.0, 32000.0, 44100.0, 48000.0, 88200.0, 96000.0, 192000.0, -1]
Dim i, printCount, err As Integer
For i = 0 To standardSampleRates.Max
err = Pa_IsFormatSupported(inputParameters, outputParameters, standardSampleRates[i])
If err = paFormatIsSupported
If printCount = 0
Print standardSampleRates[i]
printCount = 1
Else If printCount = 4 Then
Print standardSampleRates[i]
printCount = 1
Else
Print standardSampleRates[i]
Inc printCount
Endif
Endif
Next
If Not printCount Then
Print "Nessuno\n"
Else
Print "\n"
Endif
End
