[FFmpeg-devel] GSoC project (JPEG 2000)

Peter Ross pross at xvid.org
Sun Mar 27 07:10:55 CEST 2011

On Sat, Mar 26, 2011 at 09:08:41PM -0700, rukhsana afroz wrote:
> Hi all,
> I am having compilation error while compiling ffmpeg code with jpeg 2000
> files. I put all jpeg 2000 .c and .h files in libavcodec directory. However,
> while replacing these files, I found, there are already dwt.c and dwt.h
> files in libavcodec directory. I found lots of inconsistency between current
> dwt.c/h files and jpeg2000 dwt.c/h files in terms of function parameters and
> function implementation. Therefore, i renamed jpeg2000 files to dwtg.c and
> dwtg.h and changed the corresponding refereneces in some places. My code is
> in "git at github.com:rukhsana/
> jpeg2000.git". Now, if i compile this code, i get the following error:
> CC    libavcodec/j2k.o
> libavcodec/j2k.c:168: error: no previous prototype for
> ‘ff_j2k_init_tier1_luts’
> make: *** [libavcodec/j2k.o] Error 1
> "ff_j2k_init_tier1_luts" function has been declared in j2k.h file,
> implemented in j2k.c file and has been called from j2kdec.c file. My goal is
> trying to decode a j2k file by the current decoder. I have read one book and
> the specification on jpeg 2000. Now, i am not totally illeterate for jpeg
> 2000 coding standard.
> If anybody could help me on getting rid of current compilation error, that
> would be great for me.

The FFmpeg build system forbids the use of global functions, without a previous
prototype declaration. To fix this, you need to declare a 'ff_j2k_init_tier1_luts'
prototype somewhere _or_ make the function static.

From the gcc manpage:
   -Wmissing-prototypes (C and Objective-C only)
       Warn if a global function is defined without a previous prototype declaration.  This warning is issued even if
       the definition itself provides a prototype.  The aim is to detect global functions that fail to be declared in
       header files.

-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
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