update - changing palette from YUYV to BA81 at 352x288 has removed horizontal breakup in capture on kworld usb2800. (Not tried; higher resolutions/ easycap device yet )
which leads to;
Subsequently changed "height >>= norm_maxh(dev)" to "height = norm_maxh(dev) >> 1" to /linux/drivers/media/video/em28xx/em28xx-core.c in my media-build tree from linuxtv.org. Did a make all and a make install (not ./build which gets new sources) and a reboot. Refer to the links above for a fuller explanation.
I have a choppy picture (horizontal blocking and artefacts/lines) with an Easycap DC60 on my Raspberry Pi, but at least it's a picture.
The KWorld USB2800 is producing some pictures too. Similar patterns of break up.