[vlc-devel] Starting Scaletempo for VLC

Antoine Cellerier dionoea at videolan.org
Mon Jun 9 09:28:22 CEST 2008

On Fri, Jun 06, 2008, Rov Juvano wrote:
> I have the resampling code written but I'll need some help
> gluing it into VLC.  Like:
> - Where to hook into the audio stream?
>   src/audio_output/input.c:aout_InputPlay? a regular filter?
> - What's its interface? a module?

A filter would definitively be the right way to go (an "audio filter2"
would be better than "audio filter" ... even though the local playback
audio engine doesn't support using "audio filter2" yet ... but that
could be changed easily)

> - Any good docs, examples, template for its interface?

Check files that match "audio filter2" in modules/audio_filter/.
The interface is defined in include/vlc_filter.h (for "audio filter2").

> - How to get samples as s16 or float?

You can restrict allowed input formats in your filter. Just return an
error in the init function if the formats you got do not suit your
needs. (Or you could just accept any input format and spawn the
appropriate audio filter module to convert to s16 if needed)

> - Anything else you think would be helpful as I get started?

Not many people (in fact, none) work on the audio output or filters
stuff nowadays ... so you're pretty much on your own. Good luck!

Antoine Cellerier

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