libmpcodecs/vd_mpng.c: In function 'pngReadFN':
libmpcodecs/vd_mpng.c:77: error: dereferencing pointer to incomplete type
libmpcodecs/vd_mpng.c: In function 'decode':
libmpcodecs/vd_mpng.c:114: error: dereferencing pointer to incomplete type
libmpcodecs/vd_mpng.c:131: error: dereferencing pointer to incomplete type
make: *** [libmpcodecs/vd_mpng.o] Error 1
make: *** Waiting for unfinished jobs....
* ERROR: media-video/mplayer-1.0_rc4_p20101114 failed (compile phase)
This looks to be a libpng 1.5 specific problem. There is a patch here:
applying this fixes the problem.
Confirmed; that file is using direct access to the png_struct and png_info_struct pointers, which is no longer permitted in libpng-1.5
*** This bug has been marked as a duplicate of bug 354965 ***