Speex dev - Dec 2004 - How to convert from Microsft PCM 16bit to float

Dear all,

I have one simple question.  I understand that
speex_encode and speex_decode takes float * as an
arguement to encode and decode the sound.  However,
when I get the PCM data from the sound card under
win32, it is a just 16 bit array.  May I know how do I
convert this 16 bit value to speex float format and to
convert back?  Is there got any routine to do this?

YueWeng


		
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Here's the gist of it... plucked from one of my directshow filters.

This assumes it's being passed an array of unsigned char (which are really 
16-bit PCM)

It basically amounts to...

FOR EACH 16-bit short sample in ShortBuffer DO
  floatBuffer[uptoSample] = ((float)(ShortBuffer[uptosample]) / 32767.0)
NEXT uptoSample


HRESULT SpeexEncodeInputPin::TransformData(unsigned char* inBuf, long 
inNumBytes) {

 //Note the 2 is because a float is twice the width of a short.
 float* locFloatBuf = new float[inNumBytes/2];

 short locTempShort = 0;
 float locTempFloat = 0;


 for (int i = 0; i < inNumBytes; i += 2) {
  locTempShort = *((short*)(inBuf + i));
  locTempFloat = (float)locTempShort;
  locTempFloat /= 32767.0;
  locFloatBuf[i/2] = locTempFloat;;
 }

 //ETC ETC ETC
}
----- Original Message ----- 
From: "Tay YueWeng" <yueweng@yahoo.com>
To: <speex-dev@xiph.org>
Sent: Tuesday, December 28, 2004 5:50 PM
Subject: [Speex-dev] How to convert from Microsft PCM 16bit to float

> Dear all,
>
> I have one simple question.  I understand that
> speex_encode and speex_decode takes float * as an
> arguement to encode and decode the sound.  However,
> when I get the PCM data from the sound card under
> win32, it is a just 16 bit array.  May I know how do I
> convert this 16 bit value to speex float format and to
> convert back?  Is there got any routine to do this?
>
> YueWeng
>
>
>
> __________________________________
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> Read only the mail you want - Yahoo! Mail SpamGuard.
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