_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.


Availability

  • QB64 v1.5 and up
  • QB64-PE all versions


Examples

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

PRINT "Loading...";
DIM Song AS LONG
Song = _SNDOPEN("onward_ride1.flac") ' Replace file name with your sound file
IF Song < 1 THEN
    PRINT "Failed to load sound!"
    END
END IF
PRINT "Done!"

DIM Channels AS _UNSIGNED _BYTE
Channels = SndChannels(Song)

IF Channels = 2 THEN
    PRINT "This file is STEREO"
ELSEIF Channels = 1 THEN
    PRINT "This file is MONO"
ELSE
    PRINT "An error occurred."
END IF

_SNDCLOSE Song 'closing the sound releases the mem blocks

END


' This function returns the number of sound channels for a valid sound "handle"
' 2 = stereo, 1 = mono, 0 = error
FUNCTION SndChannels~%% (handle AS LONG)
    DIM SampleData AS _MEM

    SndChannels = 0 ' Assume failure

    ' Check if the sound is valid
    SampleData = _MEMSOUND(handle, 0)
    IF SampleData.SIZE = 0 THEN
        EXIT FUNCTION
    END IF

    ' Check the data type and then decide if the sound is stereo or mono
    IF SampleData.TYPE = 260 THEN ' 32-bit floating point
        IF SampleData.ELEMENTSIZE = 4 THEN
            SndChannels = 1
        ELSEIF SampleData.ELEMENTSIZE = 8 THEN
            SndChannels = 2
        END IF
    ELSEIF SampleData.TYPE = 132 THEN ' 32-bit integer
        IF SampleData.ELEMENTSIZE = 4 THEN
            SndChannels = 1
        ELSEIF SampleData.ELEMENTSIZE = 8 THEN
            SndChannels = 2
        END IF
    ELSEIF SampleData.TYPE = 130 THEN ' 16-bit integer
        IF SampleData.ELEMENTSIZE = 2 THEN
            SndChannels = 1
        ELSEIF SampleData.ELEMENTSIZE = 4 THEN
            SndChannels = 2
        END IF
    ELSEIF SampleData.TYPE = 1153 THEN ' 8-bit unsigned integer
        IF SampleData.ELEMENTSIZE = 1 THEN
            SndChannels = 1
        ELSEIF SampleData.ELEMENTSIZE = 2 THEN
            SndChannels = 2
        END IF
    ELSEIF SampleData.TYPE = 0 THEN ' This means this is an OpenAL sound handle
        DIM RightChannel AS _MEM
        RightChannel = _MEMSOUND(handle, 2)
        IF RightChannel.SIZE > 0 THEN
            SndChannels = 2
        ELSE
            SndChannels = 1
        END IF
    END IF
END FUNCTION
Example 2
Plotting a sound's waves.
OPTION _EXPLICIT

DECLARE LIBRARY
    $IF 32BIT THEN
        FUNCTION ConvertOffset~& ALIAS "uintptr_t" (BYVAL o AS _UNSIGNED _OFFSET)
    $ELSE
        FUNCTION ConvertOffset~&& 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("OPL3 Groove.rad") ' replace this with your (WAV, AIFF, AIFC, FLAC, OGG, MP3, MID, IT, XM, S3M, MOD, RAD, AHX, HVL, QOA) sound file
IF Song < 1 THEN
    PRINT "Failed to load song!"
    END
END IF
PRINT "Done!"

_SNDPLAY Song

DIM SampleData AS _MEM: SampleData = _MEMSOUND(Song, 0)
IF SampleData.SIZE = 0 THEN
    PRINT "Failed to access sound sample data."
    END
END IF

DIM sz AS _UNSIGNED _INTEGER64: sz = ConvertOffset(SampleData.ELEMENTSIZE) ' sz is the total size of the sound in bytes
DIM x AS LONG, i AS _UNSIGNED _INTEGER64

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

    $CHECKING:OFF
    IF SampleData.TYPE = 130 THEN ' 128 OR 2: integer stereo or mono
        FOR x = 0 TO _WIDTH - 1
            DIM si AS INTEGER: si = _MEMGET(SampleData, SampleData.OFFSET + i + x * sz, INTEGER) ' get sound data
            LINE (x, _HEIGHT / 2)-STEP(0, 300 * si / 32768), _RGB32(0, 111, 0) 'plot wave
        NEXT
    ELSEIF SampleData.TYPE = 260 THEN ' 256 OR 4: floating point stereo or mono
        FOR x = 0 TO _WIDTH - 1
            DIM sf AS SINGLE: sf = _MEMGET(SampleData, SampleData.OFFSET + i + x * sz, SINGLE) ' get sound data
            LINE (x, _HEIGHT / 2)-STEP(0, sf * 300), _RGB32(0, 111, 0) 'plot wave
        NEXT
    ELSEIF SampleData.TYPE = 1153 THEN ' 128 OR 1 OR 1024: unsigned byte stereo or mono
        FOR x = 0 TO _WIDTH - 1
            DIM sb AS _BYTE: sb = _MEMGET(SampleData, SampleData.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 IF
    $CHECKING:ON

    _DISPLAY
    _LIMIT 60

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

_SNDCLOSE Song ' closing the sound releases the mem blocks
_AUTODISPLAY
END


See also


Navigation:
Main Page with Articles and Tutorials
Keyword Reference - Alphabetical
Keyword Reference - By usage
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