[Alsaplayer-devel] Time stretch with soundtouch

[Dominique Michel]

Le Sat, 14 Jul 2007 23:12:10 +0200,
"Luis Garrido" <luisgarrido at users.sourceforge.net> a écrit :

> Hi there!
> 
> I need a media player that can loop a section of an audio file and
> apply time stretching and transposition to it. The most obvious
> solution is adding support for the SoundTouch library to an existing
> media player.
> 
> I am making a survey about which media player framework could make my
> work easier.
> 

Time stretching implies at the input must be able to slow down and up.
AlsaPlayer have the best speed capability of all the free player I know. And
loop into a selection is already implemented. So, I think at it can be a very
good choice for what you want to do.

> Can someone plese hint how would one go around this within AlsaPlayer?
> 

It is hard for me to give you a precise answer because I am just the
administrator, not a developer. 

You can look into app/CorePlayer.cpp, app/Main.cpp and app/Effect.cpp

Be aware at AlsaPlayer use integers for all its internal sound representation.
That is not optimal in regard to sound quality for output plugins like jack or
even some floating point sound formats. We are currently discussing to change
this and use float instead of int, but I cannot give you any delay at that
time.

I am looking for some volunteer(s) to do that because it will take months
or years if I try to do that myself. I begun to learn the C language, but most
of my spare time go to administrate AP and I already don't have enough time to
learn the C (and I have still C++ to learn too...). And it is summer now...

Anyway, it will be very nice if you choose AlsaPlayer to implement time
stretching and transposition, that with or without changing the internal sound
representation from int to float. Please, keep us aware of what you choose, and
if you choose AP, I will be very open to any kind of cooperation, both on that
list or private. I can even give you svn access if you want to.

I also think at other on this list can give you a more precise answer about the
technical aspect of this soundtouch implementation.

Cheers,
Dominique

> Thanks,
> 
> L
>