_MEMSOUND

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The _MEMSOUND function returns a _MEM value referring to a sound's raw data in memory using a designated sound handle created by the _SNDOPEN or _SNDNEW function.


Syntax

soundBlock = _MEMSOUND(soundHandle&[, channel&])


Parameters

  • The soundBlock _MEM type variable holds the read-only elements .OFFSET, .SIZE, .ELEMENTSIZE, .TYPE and .SOUND.
    • .OFFSET is the starting memory address of the sound sample data.
    • .SIZE is the size of the sample data in bytes
    • .ELEMENTSIZE will contain the number of bytes-per-sample the audio contains.
      • Can return 1 (8-bit mono), 2 (8-bit stereo), 2 (16-bit mono), 4 (16-bit stereo), 4 (32-bit mono) or 8 (32-bit stereo).
      • Use .TYPE to determine the data type of the sample data.
    • .TYPE will contain the data type of the sample data. See _MEM for details.
    • .SOUND will contain the same handle value as returned by the _SNDOPEN function.
  • The second parameter channel& is optional and deprecated. This was used to specify the sound channel. In QB64-PE v3.1.0 and above stereo data is always interleaved. You must use .ELEMENTSIZE and .TYPE to determine the type of audio data you are dealing with.


Description

  • Use this function to obtain a pointer to the raw sound data in memory for direct access.
  • Even if the memory pointer obtained by this fuction was already freed again using _MEMFREE, the respective Sound handle itself must still be freed using _SNDCLOSE when no longer required.
  • If .SIZE returns 0, that means the data could not be accessed. It may happen if you try to access the right channel in a mono file or the format simply does not support accessing raw PCM samples.
  • channel& - 1 (left channel/mono) or 2 (right channel; for stereo files) was supported on the old OpenAL backend. For the new miniaudio backend, this must be 0.
  • _MEMSOUND does not work for sounds loaded with _SNDOPEN when using the STREAM or NODECODE flags.


Availability

  • v1.5

    v1.5

  • all

    all

  • Apix.png
  • yes

    yes

  • yes

    yes

  • yes

    yes


Examples

Example 1
Checking that a sound file is stereo.
OPTION _EXPLICIT

CONST FILE_FILTER = "*.wav|*.aiff|*.aifc|*.flac|*.ogg|*.mp3|*.it|*.xm|*.s3m|*.mod|*.rad|*.ahx|*.hvl|*.mus|*.hmi|*.hmp|*.hmq|*.kar|*.lds|*.mds|*.mids|*.rcp|*.r36|*.g18|*.g36|*.rmi|*.mid|*.midi|*.xfm|*.xmi|*.qoa"

PRINT "Loading...";
DIM Song AS LONG
Song = _SNDOPEN(_OPENFILEDIALOG$("Open audio file", , FILE_FILTER))
IF Song < 1 THEN
    PRINT "Failed to load sound!"
    END
END IF
PRINT "Done!"

DIM channels AS _UNSIGNED _BYTE: channels = SndChannels(Song)

IF channels THEN
    PRINT "This sound data has"; channels; "channels."
ELSE
    PRINT "An error occurred."
END IF

_SNDCLOSE Song

END

' This function returns the number of sound channels for a valid sound handle
FUNCTION SndChannels~%% (handle AS LONG)
    DECLARE LIBRARY
        ' This is needed to convert _OFFSET to LONG / _INTEGER64
        $IF 32BIT THEN
            FUNCTION SndChannels.CLngPtr~& ALIAS "uintptr_t" (BYVAL o AS _UNSIGNED _OFFSET)
        $ELSE
            FUNCTION SndChannels.CLngPtr~&& ALIAS "uintptr_t" (BYVAL o AS _UNSIGNED _OFFSET)
        $END IF 
    END DECLARE

    DIM soundData AS _MEM: soundData = _MEMSOUND(handle)

    IF soundData.SIZE THEN
        ' See https://qb64phoenix.com/qb64wiki/index.php/MEM for details
        SELECT CASE soundData.TYPE
            CASE 260 ' 32-bit floating point
                SndChannels = SndChannels.CLngPtr(soundData.ELEMENTSIZE) \ _SIZE_OF_SINGLE

            CASE 132 ' 32-bit signed integer
                SndChannels = SndChannels.CLngPtr(soundData.ELEMENTSIZE) \ _SIZE_OF_LONG

            CASE 130 ' 16-bit signed integer
                SndChannels = SndChannels.CLngPtr(soundData.ELEMENTSIZE) \ _SIZE_OF_INTEGER

            CASE 1153 ' 8-bit unsigned integer
                SndChannels = SndChannels.CLngPtr(soundData.ELEMENTSIZE) \ _SIZE_OF_BYTE

            CASE ELSE ' unknown format
                SndChannels = 1
        END SELECT
    END IF

    IF soundData.SOUND = handle THEN _MEMFREE soundData
END FUNCTION
Example 2
Plotting a sound's waves.
OPTION _EXPLICIT

CONST FILE_FILTER = "*.wav|*.aiff|*.aifc|*.flac|*.ogg|*.mp3|*.it|*.xm|*.s3m|*.mod|*.rad|*.ahx|*.hvl|*.mus|*.hmi|*.hmp|*.hmq|*.kar|*.lds|*.mds|*.mids|*.rcp|*.r36|*.g18|*.g36|*.rmi|*.mid|*.midi|*.xfm|*.xmi|*.qoa"

DECLARE LIBRARY
    ' This is needed to convert _OFFSET to LONG / _INTEGER64
    $IF 32BIT THEN
        FUNCTION CLngPtr~& ALIAS "uintptr_t" (BYVAL o AS _UNSIGNED _OFFSET)
    $ELSE
        FUNCTION CLngPtr~&& ALIAS "uintptr_t" (BYVAL o AS _UNSIGNED _OFFSET)
    $END IF 
END DECLARE

SCREEN _NEWIMAGE(800, 327, 32)

PRINT "Loading...";
DIM Song AS LONG
Song = _SNDOPEN(_OPENFILEDIALOG$("Open audio file", , FILE_FILTER))
IF Song < 1 THEN
    PRINT "Failed to load sound!"
    END
END IF
PRINT "Done!"

_SNDPLAY Song

DIM soundData AS _MEM: soundData = _MEMSOUND(Song, 0)

IF soundData.SIZE = 0 THEN
    PRINT "Failed to access sound sample data."
    END
END IF

DIM sz AS _UNSIGNED _INTEGER64: sz = CLngPtr(soundData.ELEMENTSIZE)
DIM x AS LONG, i AS _UNSIGNED _INTEGER64

DO UNTIL _KEYHIT = 27 OR NOT _SNDPLAYING(Song) OR i + (_WIDTH * sz) > soundData.SIZE
    CLS
    LOCATE 1, 1: PRINT i; "/"; soundData.SIZE, "Frame Size ="; sz, "Data Type ="; soundData.TYPE

    ' See https://qb64phoenix.com/qb64wiki/index.php/MEM for details
    SELECT CASE soundData.TYPE
        CASE 130 ' integer stereo or mono
            FOR x = 0 TO _WIDTH - 1
                DIM si AS INTEGER: si = _MEMGET(soundData, soundData.OFFSET + i + x * sz, INTEGER) ' get sound data
                LINE (x, _HEIGHT \ 2)-STEP(0, 300! * si / 32768!), _RGB32(0, 111, 0) 'plot wave
            NEXT

        CASE 132 ' long stereo or mono
            FOR x = 0 TO _WIDTH - 1
                DIM sl AS LONG: sl = _MEMGET(soundData, soundData.OFFSET + i + x * sz, LONG) ' get sound data
                LINE (x, _HEIGHT \ 2)-STEP(0, 300! * sl / 2147483648!), _RGB32(0, 111, 0) 'plot wave
            NEXT

        CASE 260 ' floating point stereo or mono
            FOR x = 0 TO _WIDTH - 1
                DIM sf AS SINGLE: sf = _MEMGET(soundData, soundData.OFFSET + i + x * sz, SINGLE) ' get sound data
                LINE (x, _HEIGHT \ 2)-STEP(0, sf * 300!), _RGB32(0, 111, 0) 'plot wave
            NEXT

        CASE 1153 ' unsigned byte stereo or mono
            FOR x = 0 TO _WIDTH - 1
                DIM sb AS _BYTE: sb = _MEMGET(soundData, soundData.OFFSET + i + x * sz, _UNSIGNED _BYTE) XOR &H80 ' get sound data and convert to signed
                LINE (x, _HEIGHT \ 2)-STEP(0, 300! * sb / 128!), _RGB32(0, 111, 0) ' plot wave
            NEXT
    END SELECT

    _DISPLAY

    _LIMIT 60

    i = FIX(_SNDGETPOS(Song) * _SNDRATE) * sz ' calculate the new sample frame position
LOOP

_SNDCLOSE Song
_AUTODISPLAY
END


See also


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