[MPlayer-dev-eng] Audio visualization

[Nico Sabbi]

On Wednesday 30 January 2008 18:05:35 Andrew Calkin wrote:
> > > Check out libvisual, and search the MPlayer m/l archives. There
> > > is already plugin support for MPlayer in libvisual, apparently.
> >
> > As I understood, there is xmms is needed for using mplayer with
> > libvisual and its xmms-plugins. If it is true, IMHO it is too
> > inconvenient for lots of application and bulky.
> >
> > I think there is another and more powerfull approach could
> > be used to add this feature to mplayer without xmms and
> > libvisual. It could be implemented as additional feature which is
> > enabled in command line (maybe with -viz [oscill | spectrum | ...
> > ]) only if only one stream is present - audio.
> >
> > This feature could be useful for various diagnostic / test /
> > demonstration purposes.
> >
> > Any advices / objections?
> >
> > Thank you for your consideration.
>
> IIRC, the issue was the messing with video and audio streams. The
> way it was implemented before was that the audio was output via an
> audio fifo to libvisual as well as the regular output. Then
> libvisual generated the required images using optimized routines
> and exported those images to a fifo. The image fifo was read by -vf
> bmovl and used to display the image on MPlayer vo.
>
> IMHO I really think that reinventing the wheel in terms of
> re-writing libvisual image creation algs is not such a good idea,
> and the internal messing with audio/video streams would not be
> accepted into MPlayer (at least that was the stance of developers
> some years ago, according to m/l archives I looked at, IIRC). The
> export of audio and import of the video overlay images was at least
> tolerated. I am not sure how the audio export/bypass worked
> exactly, but surely you can google the m/l thread from years back,
> as I did.
>
> See the thread from around 2003-11-14 by Gustavo Sverzut Barbieri.
> I don't think the export audio stuff was limited to xmms, a
> libvisual plugin to interface exists for libvisual, which i _think_
> can interface with the exported audio fifo directly.
>

you can  use something like the following without messing with
source code:
$ mplayer /dev/zero -demuxer rawvideo -rawvideo 
fps=25:w=640:h:480 -audiofile file.mp3 -vf bmovl ...

or, if the visual lib creates a fifo,
$ mplayer visual.fifo -demuxer rawvideo -rawvideo 
fps=25:w=640:h:480 -audiofile file.mp3