[pulseaudio-discuss] Resampling, Duplicate Front to Rear, and few other questions

Hofmann, Laurent laurent at kally.net
Mon Apr 2 11:14:06 PDT 2007

> -----Message d'origine-----
> De : pulseaudio-discuss-bounces at mail.0pointer.de
[mailto:pulseaudio-discuss-bounces at mail.0pointer.de] De la part de Pierre
> Envoyé : lundi 2 avril 2007 08:32
> À : General PulseAudio Discussion
> Objet : Re: [pulseaudio-discuss] Resampling, Duplicate Front to Rear, and
few other questions
> It's far from trivial to do such a thing. And the setup time for a sound
card (you can't just change sample rate) can be rather long. In other words,
> it would be a nice feature but too much work with too little gain for any
of the main developers to look at it anytime soon.

I think it is not only a nice feature but a key feature ! All modern
soundcards are able to do resampling in a better way than any other program,
without costing any CPU time. When I read a sound not resampled, pulseaudio
takes 20% CPU. If it must be resampled, even with the most basic algorithm,
pulsaudio takes more than 50% CPU (On my box).

Even with a powerfull computer, resampling for nothing costs a lot. Let's
imagine a video game with nice sound FX and music at 48Khz whereas pulsaudio
is set up at 44Khz : depending on the priority, either the 3D image or the
sound will be hashed...

Since I can switch the sample rate in the conf and stop/start pulseaudio,
why this couldn't be done automatically ?

> If you have two sound devices representing front and back, then combining
them with the default channel map should work.
> In the longer run, the internal channel remapper should be taught how to
handle such cases.

I Have not two sound devices, I have one with 6 channels...

> There is some driver for EsounD and NT4, but I haven't seen anything
newer. Windows' is nowhere near as flexible as most Unix systems, so it's
> difficult to achieve this. Not impossible though, so if you have a lot of
free time on your hands. ;)

The ESD NT4 driver works well but is old and lacking some parts of dev. I
tried to recompile it for Windows XP but I did not even managed to make the
DDK of Windows XP work.

Apart from that, seeing support of ESD in VLC (ESD is already supported in
unix version but not on the win32 version) or a native pulseaudio support in
VLC (both unix and win32) would be a good start.

Best Regards,

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