Re: wavemap: Avoid resampling if possible

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 
> Date: 2002/12/13 Fri PM 03:42:07 EST
> To: [e-mail]
> 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 <[e-mail]>
>
> -
>
> 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
> [e-mail]
> 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 */

wavemap: Avoid resampling if possible

[Francois Gouget]

On Fri, 13 Dec 2002 [e-mail] wrote:
> 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.

We could, but then it seems the future is that Wine with more often use
the Jack or aRts drivers than our current wineoss driver. So we will
automatically benefit from Jack's or aRts resampling capabilities.

Improving our resampling code might still be useful for NAS or Alsa
though I'm not really sure about that. That would be something to check
and if neither of these two needs resampling in wine then we should go
the the resampling solution that requires the least maintenance.

(and it might even be that copy/pasting another project's code would
require less maintenance...)

wavemap: Avoid resampling if possible

[Chris Morgan]

On Saturday 14 December 2002 02:41 pm, Francois Gouget wrote:
> On Fri, 13 Dec 2002 [e-mail] wrote:
> > 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.
>
> We could, but then it seems the future is that Wine with more often use
> the Jack or aRts drivers than our current wineoss driver. So we will
> automatically benefit from Jack's or aRts resampling capabilities.

I'm kind of hoping arts is replaced with jack as jack is suitable for both 
desktop and professional audio users.  The jack developers are reluctant to 
put resampling inside of the server, they would rather the client resampled 
using a library like the one I suggested.  The intent is to keep the server 
simpler.  I'm not sure if they will change their mind when jack is more 
widely used for general purpose audio like we are doing with wine.

Chris