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

Calculating dependencies... done!
[ebuild  N    ] media-libs/libdca-0.0.5  USE="-debug -oss" 385 kB [0]
[ebuild  N    ] media-video/avidemux-2.4.1  USE="aac alsa arts dts jack lame truetype vorbis x264 xv xvid -aften -amrnb -encode -esd -gtk -libsamplerate -qt4" 5,653 kB [0]
[blocks B     ] media-libs/libdts (is blocking media-libs/libdca-0.0.5)

Total: 2 packages (2 new, 1 block), Size of downloads: 6,037 kB
Portage tree and overlays:
 [0] /usr/portage