[sdlsound] tremor and MAD?

Glenn Maynard g_sdl at zewt.org
Mon Jan 13 04:38:58 EST 2003


On Mon, Jan 13, 2003 at 04:17:54AM -0500, Ryan C. Gordon wrote:
> > Would it be possible to use the Tremor and MAD libraries in SDL_sound?
> > It would boost the performance on StrongArm processors.
> I wrote to the MAD developers for a GPL exemption, but never heard back.

LGPL libraries are GPL-compatible, so they can link to GPL libraries; no
exemption is needed.  http://www.gnu.org/philosophy/license-list.html

The trouble that comes up is that only GPL-compatible code can link to
GPL'd code (even indirectly, through another library), so if MAD is
linked to SDL_sound, the extra permissions granted by the LGPL are 
unavailable, since using them would violate MAD's license.  However,
SDL_sound is still LGPL and the permissions can still be used if MAD
isn't linked (eg. SMPEG or MPGLIB is used instead).

If the GPL library being linked by an LGPL library was not optional--if
the only way to compile the lib is to use the library--then there's no
choice, and the program is effectively GPL (unless a replacement is
written).  In other words, MAD can't replace SMPEG and MPGLIB.

Glenn Maynard

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