[gst-devel] libmpg123 decoder plugin

[Roland Poppenreiter]

* On Thu, 15 Jan 2009 at  7:47 +0200, Felipe Contreras wrote:
> On Wed, Jan 14, 2009 at 5:41 PM, Roland Poppenreiter <r_poppi at gmx.at> wrote:
> > Hello everybody,
> >
> > I hope this is the right mailinglist for this anouncement.  I wrote
> > a mp3 decoder plugin with the mpg123 library. One reason is that
> > mpg123 has some processor optimization (SSE, MMX, 3DNow, ...) in it
> > and should be faster than the mad decoder. I used the mad decoder
> > plugin (gstmad.c) as template for my plugin - so they are quite
> > similar. I wanted to benchmark both decoders and compare the results
> > but I ran into several problems and I got a few questions:
> >
> >  - sometimes i get a short white noise sound when i start playing an
> >   mp3 file with my mpg123 decoder plugin.
> >  - short white noise sound appears after seeking as well.
> >  - is it possible that data comming from the filesrc is sometimes
> >   overlapping?
> >  - seeking is not always working, also not with the mad decoder.
> 
> Are you using the mp3parse element?
 
no, I dont even know this plugin ....
the pipeline I'm using is this:

gst-launch filesrc location="foo.mp3" ! mpg123 ! audioconvert !
osssink

> >  - the mad decoder decodes mpg samples to audio/x-raw-int 32 Bit,
> >   but most extensions (SSE, MMX, ...) can just handle 16 Bit
> >   samples, therefore I would preferre 16 Bit audio/x-raw-int as
> >   output for my decoder.
> 
> Then output that.

okay, fine!

> Is that mpg123 library new? If I recall correctly the last time I
> tried it wasn't there, I even suggested them to create a library, but
> they didn't look too interested.

the libmpg123 is not new, its the api from the mpg123 mp3-player
(http://www.mpg123.de/api/) and I already used it for my mpg123
gstreamer plugin.

> Another option is to provide an OpenMAX IL API for the library. In
> that case the gst-openmax wrapper would be able to use the decoder
> transparently.

I dont know this library, I will take a look at it, but for the
moment I have to solve my problems with the mpg123 plugin. 

> -- 
> Felipe Contreras
> 

-- Roland Poppenreiter