wavemap: Avoid resampling if possible

[chrismorgan at rcn.com]

There was someone on the jack mailing list that was working on a resampling library.  This would be something we could replace our resampling code with.  More than likely the library would support several resampling algorithms allowing  for an appropriate one to be selected based on cpu speed and quality.  I'll mail the jack devel list and see if there is any new status on the progress of the library.

Thanks,
Chris


> 
> From: Francois Gouget <fgouget at codeweavers.com>
> Date: 2002/12/13 Fri PM 03:42:07 EST
> To: wine-patches at winehq.com
> Subject: wavemap: Avoid resampling if possible
> 
> 
> The distorsion that lead to my previous patch was in fact caused by the 
> resampling of an 11025Hz signal to 48kHz. According to the signal 
> processing literature I could find, what we do is a '1st Order Linear 
> Interpolation Filter' and that is considered a poor filter. That 
> literature says we should be using an 'nth Order Interpolation / 
> Decimation' filter.
> 
> I didn't really feel motivated enough to implement such a beast, plus 
> this is more the job of a sound library than of Wine. I hope aRts, 
> ESound, Jack and friends implement such a filter so it will hopefully 
> soon be a moot point soon anyway. However one easy thing we can do is to 
> try not to do any resampling unless absolutely necessary. This means 
> first trying simple 8/16bits or mono/stereo conversions first. If we 
> find a match the sound quality will be better and the conversion will 
> use less CPU.
> 
> 
> Changelog:
> 
>     Francois Gouget <fgouget at codeweavers.com>
> 
>   * dlls/winmm/wavemap/wavemap.c
> 
>     Our resampling algorithm is quite primitive so try simple 8/16 
> mono/stereo conversions first. Only resample if we cannot avoid it.
> 
> 
> -- 
> Francois Gouget
> fgouget at codeweavers.com
> 
> 
> Index: dlls/winmm/wavemap/wavemap.c
> ===================================================================
> RCS file: /home/wine/wine/dlls/winmm/wavemap/wavemap.c,v
> retrieving revision 1.26
> diff -u -r1.26 wavemap.c
> --- dlls/winmm/wavemap/wavemap.c	13 Dec 2002 02:18:20 -0000	1.26
> +++ dlls/winmm/wavemap/wavemap.c	13 Dec 2002 19:18:56 -0000
> @@ -185,6 +191,19 @@
>  #define	TRY(sps,bps)    wfx.nSamplesPerSec = (sps); wfx.wBitsPerSample = (bps); \
>                          if (wodOpenHelper(wom, i, lpDesc, &wfx, dwFlags | WAVE_FORMAT_DIRECT) == MMSYSERR_NOERROR) \
>                          {wom->avgSpeedInner = wfx.nAvgBytesPerSec; goto found;}
> +
> +        /* Our resampling algorithm is quite primitive so first try
> +         * to just change the bit depth and number of channels
> +         */
> +        for (i = ndlo; i < ndhi; i++) {
> +            wfx.nSamplesPerSec=lpDesc->lpFormat->nSamplesPerSec;
> +            wfx.nChannels = lpDesc->lpFormat->nChannels;
> +            TRY(wfx.nSamplesPerSec, 16);
> +            TRY(wfx.nSamplesPerSec, 8);
> +            wfx.nChannels ^= 3;
> +            TRY(wfx.nSamplesPerSec, 16);
> +            TRY(wfx.nSamplesPerSec, 8);
> +        }
>  
>          for (i = ndlo; i < ndhi; i++) {
>              /* first try with same stereo/mono option as source */
> 
>