Audio output 3 status & call for contributors

Christophe Massiot massiot at
Thu Aug 8 00:58:56 CEST 2002

As you have noticed, the audio layer has been totally rewritten in 
the latest CVS. Almost all architectures are now broken, and probably 
on the few architectures/files which work, there are a number of 
major issues.

The reason why it is broken everywhere is because many filter modules 
are missing. Sam and I will try to fix that. However, contributors 
are welcome, and many tasks are not very difficult.

TODO list :

[aout core]
- have working lipsync [Meuuh]
- fix annoying starvations [Meuuh]
- allow the user to insert/remove aout filters
- have a way to implement S/PDIF [Meuuh]

Only the liba52 plug-in is supported at present. Other codecs must be 
ported to the new architecture (and will require certain aout 
converters) :
- libmad
- lpcm

[audio output modules]
Only macosx, sdl have been ported to the new architecture (with 
numerous remaining problems). A new file plug-in has been added to 
write the output stream to a file (for the moment it causes many 
problems, so people'd probably better disable it in Makefile.config).
- esd
- alsa [bozo]
- oss [sam]
- waveout
- directx
- beos
- arts

[audio mixer modules]
Only a trivial mixer has been implemented for the moment. It takes 
only the first input stream, and downmixing is done by deleting extra 
channels. It works with float32 and fixed32.
- write float32 and fixed32 real mixers
- write a S/PDIF-capable pseudo-mixer [Meuuh]

[audio filters : converters]
Aout3 needs to convert samples to/from float32/fixed32. At present 
only float32tos16 has been written.
- s16tofloat32
- s16tofixed32
- fixed32tofloat32
- u16tofloat32
- u16tofixed32
- s8tofloat32
- s8tofixed32
- u8tofloat32
- u8tofixed32
(fixed32 is equivalent to libmad's mad_fixed_t)

[audio filters : resamplers]
Currently no resampling is done (which is why lipsync doesn't work).
- float32 resampler
- fixed32 resampler

[audio filters : misc]
- volume & balance
- visualization/scope

Before starting to work on something, post in the vlc-devel a mail 
"I'm doing this before ...". To avoid having two people working on 
the same thing.


Christophe Massiot.

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