sudo emerge -av media-video/dvdstyler

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild N ] dev-libs/libxdg-basedir-1.2.0-r1::dev-kit USE="-doc -static-libs" 30 KiB
[ebuild N ] media-libs/libfpx-1.3.1_p10:0/1::media-kit USE="-static-libs" 2,303 KiB
[ebuild N ] media-gfx/potrace-1.15::media-kit USE="-metric -static-libs" 636 KiB
[ebuild N ] media-libs/wxsvg-1.5.11:0/3::media-kit USE="(-libav) -static-libs" 503 KiB
[ebuild N ] app-cdr/dvdisaster-0.79.5::nokit USE="nls -debug" L10N="-cs -de -it -pt-BR -ru -sv" 8,032 KiB
[ebuild N ] media-libs/libwmf-0.2.8.4-r7::media-kit USE="X -debug -doc -expat" 2,119 KiB
[ebuild N ] dev-libs/imath-3.1.3:0/3.1.3::dev-kit USE="python -doc -large-stack -static-libs -test" PYTHON_SINGLE_TARGET="python3_7 -python3_8 -python3_9" PYTHON_TARGETS="python3_7 -python3_8 -python3_9" 558 KiB
[ebuild N ] app-cdr/cdrtools-3.02_alpha09-r2::media-kit USE="acl filecaps nls unicode -caps (-selinux)" 2,107 KiB
[ebuild N ] virtual/cdrtools-0::core-kit 0 KiB
[ebuild N ] media-libs/openexr-3.1.3:0/3.1.3::media-kit USE="-examples -large-stack -static-libs -test -threads -utils" CPU_FLAGS_X86="avx" 19,848 KiB
[ebuild N ] media-gfx/imagemagick-7.1.0.16:0/7.1.0.16::media-kit USE="X bzip2 cxx djvu fpx hdri jbig jpeg jpeg2k lcms openexr openmp png svg tiff truetype webp wmf xml zlib -corefonts -fftw -fontconfig -graphviz -heif -lqr -lzma -opencl -pango -perl -postscript -q32 -q8 -raw -static-libs -test -zip" 14,904 KiB
[ebuild N ] app-cdr/dvd+rw-tools-7.1-r3::media-kit 138 KiB
[ebuild N ] media-video/dvdauthor-0.7.2-r2::media-kit USE="imagemagick -graphicsmagick" 634 KiB
[ebuild N ] virtual/imagemagick-tools-0::media-kit USE="jpeg png svg tiff -perl" 0 KiB
[ebuild N ] media-libs/xine-lib-1.2.9-r2:1::media-kit USE="X a52 aac aalib alsa bluray css dts flac gtk imagemagick ipv6 jpeg mad mmap mng nls opengl sdl theora truetype v4l vaapi vdpau vorbis vpx wavpack xcb xinerama xv (-altivec) -dvb -dxr3 -fbcon -jack (-libav) -libcaca -modplug -musepack -oss -pulseaudio -samba -speex -vcd -vdr (-vidix) (-vis) -xvmc" 5,060 KiB
[ebuild N ] media-video/xine-ui-0.99.10::media-kit USE="X aalib curl nls readline xinerama -debug -libcaca -lirc -vdr" 1,722 KiB
[ebuild N ] media-video/dvdstyler-3.0.4::media-kit USE="udev -debug (-libav)" 8,663 KiB
[blocks B ] dev-libs/imath:0 ("dev-libs/imath:0" is hard blocking dev-libs/imath-3.1.3)

Total: 17 packages (17 new), Size of downloads: 67,250 KiB
Conflict: 1 block (1 unsatisfied)

• Error: The above package list contains packages which cannot be
• installed at the same time on the same system.

(dev-libs/imath-3.1.3:0/3.1.3::dev-kit, ebuild scheduled for merge) pulled in by
>=dev-libs/imath-3.1.0:= required by (media-libs/openexr-3.1.3:0/3.1.3::media-kit, ebuild scheduled for merge) USE="-examples -large-stack -static-libs -test -threads -utils" CPU_FLAGS_X86="avx"

It looks like dvdstyler wants the wrong version of dev-libs/imath.

I actually had issues with doing world updates on a system where dvdstyler was already installed due to this block, and now I cannot reinstall it.