[Libav-user] reduce dll size

Camera Man i.like.privacy.too at gmail.com
Tue Mar 11 04:45:29 CET 2014

On 03/10/2014 07:39 PM, Carl Eugen Hoyos wrote:

 > Camera Man <i.like.privacy.too at ...> writes:
 >> However, the license (LGPL) requires that you let
 >> user upgrade the library without your help. That is
 >> usually easy to achieve when you ship .dlls, but
 >> not as easy when you do static linking. If you use
 >> a GPL component (e.g. the x264 encoder), you will
 >> need to make your project GPL as well
 > But I wonder now if there is a reason that your next
 > sentence speaks about the GPL: Don't you agree that it
 > makes no difference if you link GPL'd libraries
 > statically or dynamically?

Yes, I definitely agree - if the project is GPL, the linking (and in 
fact, binary form) shouldn't matter - the distribution should 
effectively (either directly, or by a direct immediate offer) include a 
buildable source.

I specifically mentioned GPL in the context of the x264 encoder (which 
is GPL licensed) to emphasize that the earlier discussion about the LGPL 
of "just making it possible to replace the .dll" does NOT apply once GPL 
components are involved - and x264 is one such GPL component.

Summary of my understanding:

If only LGPL ("plain" ffmpeg, for example) code is involved, then the 
requirement is to let user update LGPL components on their own. One way 
to achieve that is to use the LGPL code in a .so/.dll which can be 
replaced (however, care must be taken to make this feasible - e.g., any 
changes applied to ffmpeg must be provided to the end user in source form).

Once GPL code is involved (e.g. the libx264 encoder), then the 
requirement is for the user to be able  to rebuild everything from 
source -- effectively, to provide complete usable source code for the 
entire project that uses said code, which must also be licensed under 
the GPL itself.

I'm not a lawyer, and if one releases software, one should consult legal 
advice competent in copyrights and in the relevant jurisdiction.

Carl, thanks for all the work on ffmpeg and the help you provide on the 
mailing list.

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