Le Fri, 30 Nov 2007 00:31:09 +0100,
Rene Herman <[EMAIL PROTECTED]> a écrit :

> On 29-11-07 23:56, Antonio Dupont wrote:
> 
> > I would like to change the playback tempo of some small mp3 files.  They
> > are small voice response files and I would like them to play in a shorter
> > time. Maybe at 125% speed.
> > 
> > Is there some command in ALSA that I can use to do this?
> > 
> > I've searched around and found some things about tempo and timing, but
> > nothing that I really understood, it had more to do with building
> > applications to interface with ALSA.
> > 
> > I'm using Alsa 1.0.9rc4a with a via82xx soundcard. Sorry about the xx,
> > that what dmesg tells me.
> > 
> > Hope this is enough information for a response or some help to point me
> > in the right direction.
> 
> Here's basically wrong -- ALSA is just the final step in getting sound to 
> your ears, not the correct layer for editing sound files like you want.
> 
> You can do what you want with tools like "sox", which you'll probably have 
> installed. First, note that mp3 is not a nice format to do sound processing 
> on given that it's a lossy compression format. Most installations of sox 
> will be able to do so though. Check the "supported sound formats" in the 
> "sox -h" output.
> 
> Then, you can use either the "speed" or (not affecting the pitch) "stretch" 
> effects. Ie,
> 
> $ sox foo.mp3 -t alsa default speed 1.25
> 
> or
> 
> $ sox foo.mp3 -t alsa default stretch 0.8
> 
> Hope that helps. The sox manpage is a source of further information.
> 
> Rene.
> 

You can also use a player like alsaplayer or mplayer. Both have speed control
(even reverse speed for alsaplayer). alsaplayer have a daemon mode that is
very easy to use (look at the man page).

What you must do is to start alsaplayer in the daemon mode in one console, and
you can send files and commands from another console. The other interfaces
will accept the commands too.

Dominique

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