ISpeechRecoResult::AudioFormat Property (SAPI 5.3)

Speech API 5.3
Microsoft Speech API 5.3

Object: ISpeechRecoResult

AudioFormat Property

The AudioFormat property gets or sets the audio stream format.

The controlling recognition context must retain the audio portion of the recognition. By default, a recognition context does not retain audio; that is, RecoContext.RetainedAudio is set to SRAONone. Attempts to access this retained audio stream, including references to AudioFormat, cause an SPERR_NO_AUDIO_DATA error. To retain the audio, use ISpeechRecoContext.RetainedAudio passing SRAORetainAudio as the parameter.


Get:SpAudioFormat = ISpeechRecoResult.AudioFormat
Set:ISpeechRecoResult.AudioFormat = SpAudioFormat


The owning object.
An object variable representing an audio output device.
Get: The token represents the current audio output device of the voice.
Set: The token represents the audio output device assigned to the voice.
In either case, the format for SpAudioFormat.Type is of type SpeechAudioFormatType.


The following Visual Basic form code reads and sets the AudioFormat property of a RecoResult.

To run this code, paste it into the Declarations section of a form that contains no controls. In addition to the usual reference to the Microsoft Speech Object Library, this code also needs a reference to the simpleaudio 1.0 Type Library.

Option Explicit


' Text-to-Speech variables:
Dim WithEvents Voice As SpVoice
Dim EndofStream As Boolean
Dim AudioPlugOut As SpAudioPlug

' Speech Recognition variables:
Dim WithEvents RecoContext As SpInProcRecoContext
Dim Grammar As ISpeechRecoGrammar
Dim Recognizer As SpInprocRecognizer
Dim AudioPlugIn As SpAudioPlug

Private Sub Form_Load()

    Const Text = "One of the world's seven wonders"
    Dim Output As Variant

    On Error GoTo EH

    Set Voice = New SpVoice

    ' Set up output audio:
    Set AudioPlugOut = New SpAudioPlug
    AudioPlugOut.Init True, AUDIOFORMAT
    Set Voice.AudioOutputStream = AudioPlugOut

    ' Set up input audio:
    Set AudioPlugIn = New SpAudioPlug
    AudioPlugIn.Init False, AUDIOFORMAT
    Set Recognizer = New SpInprocRecognizer
    Set Recognizer.AudioInputStream = AudioPlugIn

    ' Set up speech recognition and explicitly set
    ' flag to retain audio portion of recognition
    ' (default behavior is not to retain):
    Set RecoContext = Recognizer.CreateRecoContext
    RecoContext.RetainedAudio = SRAORetainAudio
    Set Grammar = RecoContext.CreateGrammar(1)
    Grammar.DictationSetState SGDSActive

    ' Speak some text to be recognized.
    Voice.Speak Text, SVSFlagsAsync

    Do While EndofStream = False

        ' Get audio data from audio object.
        Output = AudioPlugOut.GetData

        ' Output audio data to input audio object--
        If (Len(Output) * 2 <> 0) Then
            AudioPlugIn.SetData (Output)
        End If


    Grammar.DictationSetState SGDSInactive

    If Err.Number Then ShowErrMsg
End Sub

Private Sub RecoContext_Recognition _
   (ByVal StreamNumber As Long, _
    ByVal StreamPosition As Variant, _
    ByVal RecognitionType As SpeechLib.SpeechRecognitionType, _
    ByVal Result As SpeechLib.ISpeechRecoResult)

    Dim GetFormat As SpAudioFormat
    Dim SetFormat As SpAudioFormat

    On Error GoTo EH

    ' Get audio format.
    Set GetFormat = Result.AUDIOFORMAT

    ' Set audio format:
    Set SetFormat = CreateObject("SAPI.SpAudioFormat")
    SetFormat.Type = SAFT11kHz16BitMono
    Set Result.AUDIOFORMAT = SetFormat


    If Err.Number Then ShowErrMsg
End Sub

Private Sub Voice_EndStream _
   (ByVal StreamNumber As Long, _
    ByVal StreamPosition As Variant)

    EndofStream = True

End Sub

Private Sub ShowErrMsg()

    ' Declare identifiers:
    Const NL = vbNewLine
    Dim T As String

    T = "Desc: " & Err.Description & NL
    T = T & "Err #: " & Err.Number
    MsgBox T, vbExclamation, "Run-Time Error"

End Sub