[vlc-devel] Re: Usage of internal ffmpeg symbols

Benjamin Pracht bigben+spam at videolan.org
Sat May 27 14:37:38 CEST 2006

Le samedi 27 mai 2006 à 13:16 +0200, Diego 'Flameeyes' Pettenò a écrit :
> Hi,
> I was working in the past hours on making ffmpeg support -fvisibility=hidden 
> attribute so that the exported symbols can be reduced to the actually used, 
> allowing ffmpeg to know what other packages might be using of its API.
> Unfortunately it seems like vlc uses two symbols that are not exported by the 
> installed headers and should only be used internally:
> encoder.c:extern int16_t IMPORT_SYMBOL ff_mpeg4_default_intra_matrix[];
> encoder.c:extern int16_t IMPORT_SYMBOL ff_mpeg4_default_non_intra_matrix[];
> I can't really grok what they are supposed to be used for in this case, and 
> also lu_zero (Gentoo's ffmpeg hacker) seems not to know what they might be 
> used for outside of ffmpeg.

VLC has an option to use the mpeg4 default quantization matrix with
mpeg2 streams, as user defined quantization matrix, as it seems to give
better results with some streams. That way it uses those ffmpeg
constants to initialize the context's intra_matrix and inter_matrix
variables. Now, I guess we could include those constants in some header
on our side...


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