🚀 go-pugleaf

OK, I'm officially confused by this now.  I have a Creative Audigy2 Pro
soundcard (24 bit, external box for connections), and other sound
applications (nTrack, Creative WaveStudio) can happily record from it at
24 bits per sample, so I know it can be done.  However, doing it in my
own program turns out to be not simple, obvious or even possible as far
as I can see.

I'm familiar with the standard Win32 waveIn... functions for 16 bit
recording, and indeed my code works fine for that.  I'm less familiar
with the WAVE_FORMAT_EXTENSIBLE system, but I've read a load of stuff
from the MSDN site and it seems that subtype KSDATAFORMAT_SUBTYPE_PCM is
what I want, and use a WAVEFORMATPCMEX structure.  So far, so good, I
can open as 24 bit (or even 32 bit).  Although it seems that member
nBlockAlign has to be a power of 2, not (as for WAV files) just the
(bytes_per_sample * channels).  I'll give the code I use to open it
later...

However, when it comes to reading the data, things get surreal.  The
buffers are filled in OK (I'm using massive buffers at 64k samples long,
mainly because I want to be able to put in a breakpoint and inspect a
decent amount of data) with some sort of data.  However, it seems to be
aligned on 8-byte boundaries (fair enough, I told it nBlockAlign was 8
because it wouldn't take 6), with two floating point numbers in each
block (I found they were floats by trial and error -- mostly error --
because they weren't anything else).  OK, I can deal with floating
point, even though it seems somewhat odd.  However, the first one (left
channel) is always zero, even though the channel works fine for 16 bit
input.  The second one has reasonable data (except for an odd 'tick'
sample every 10mS (442 samples, at 44100sps), but when I convert it
from floating point back to a long I find that it's still only 16 bit
data.

At this point I am stuck.  Does anyone have any code which does 24-bit
input, in C/C++ preferably but I know enough Pascal to see what it's
doing, to see where I am going wrong?  Presumably I'm not setting
something up the way I should do...

My waveInOpen code (for 24 bits per sample):

  WAVEFORMATPCMEX fmt;

  fmt.Format.wFormatTag           = WAVE_FORMAT_EXTENSIBLE;
  fmt.SubFormat                   = KSDATAFORMAT_SUBTYPE_PCM;
  fmt.Format.nChannels            = 2;
  fmt.Format.nSamplesPerSec       = 44100;
  fmt.Format.nAvgBytesPerSec      = 44100 * 4 * 2; // rate * bytes * channels
  fmt.Format.nBlockAlign          = 8;             
  fmt.Format.wBitsPerSample       = 24;            // or 32
  fmt.Format.cbSize               = sizeof(fmt);
  fmt.Samples.wValidBitsPerSample = 24;            // or 32
  fmt.dwChannelMask               = 3;             // select both channels

  result = waveInOpen(NULL, dev, &fmt.Format, 0, 0, CALLBACK_NULL);

I've tried setting dwChannelMask to other values, only =1 opens the
device (and doesn't input anything).  Am I missing something obvious?

(Oh, I also had to write a MSVC DLL to get the KSDATAFORMAT_SUBTYPE_PCM
value, BCB provides a KsMedia.h file but not the (static) library to
link with it to get the values!  Since the library in the MS SDK is
static, it won't link with a BCB progarm...)

System:

  Athlon 1800XP, 256MB RAM
  Creative Audigy2 Pro sound card
  Windows 2000
  BCB version 6

Thanks for any help,

Chris C