[pulseaudio-discuss] SBC XQ for PA 13.0

[Pali Rohár]

On Sunday 08 December 2019 20:40:09 Andrey Semashev wrote:
> On 2019-12-07 22:31, Pali Rohár wrote:
> > On Saturday 07 December 2019 22:13:28 Andrey Semashev wrote:
> > > On 2019-12-07 21:30, Pali Rohár wrote:
> > > > 
> > > > FDK-AAC library is incompatible with any version of the GNU GPL license
> > > > and therefore it is not possible to use it in any GPL licensed software,
> > > > like pulseaudio. See: https://www.gnu.org/licenses/license-list.html#fdk
> > > 
> > > Well, incompatibility means the resulting binary is not redistributable.
> > > Users could still build PA with libfdk-aac locally.
> > 
> > Yes, you are right.
> > 
> > > Or the library could be
> > > loaded dynamically, if present on the user's system, without having to link
> > > with it at build time.
> > 
> > Some people says that this is not legal too. Loading library either at
> > build (link) time is same as at runtime... And FSF has similar
> > explanation. Main problem is that license of external library does not
> > allow you to use it in your application. And it does not depend on how
> > you build your application or how you use that library (dlopen or
> > stating or dynamic linking). You are still usage same library API. But
> > I'm not lawyer...
> > 
> > Important it that if there are people who doubt about regular usage then
> > such functionality would not be included into distribution. And above
> > dynamic loading via dlopen is a reason for doubt that something is not
> > there fully legal and can be problematic.
> > 
> > > > If there is other AAC library which license allows usage it in
> > > > pulseaudio then it could be possible. Just somebody needs to write it.
> > > 
> > > The built-in implementation in ffmpeg is under LGPL 2.1, which should be
> > > compatible.
> > 
> > Yes, LGPL 2.1 is fine.
> 
> One other question regarding libfdk-aac. Would it be ok to try using it
> through ffmpeg if it is built with it? If ffmpeg is compiled without
> libfdk-aac then we would fall back to the built-in encoder.
> 
> This would allow people who build ffmpeg themselves to use libfdk-aac. On
> the PA side, this would require very little change code-wise (it would not
> introduce build dependency on libfdk-aac), most of the integration with
> ffmpeg remains the same.

Supported A2DP codecs needs to be know at pulseaudio compile time.
So unsupported codecs are excluded from build. This is also needed to
ensure that compile time flags make sense and prevent problems that user
compiled pulseaudio with codec X, but X does not work because is not
installed available in system. So in pulseaudio's ELF binary are
correctly filled all libraries and its codecs via NEEDED flag (which is
used for generating dependences for probably all package managers).

-- 
Pali Rohár
pali.rohar at gmail.com
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