Yes, I have experience working with capturing video as a flirtation for a short time. Back in the day, none of consumer capture cards even a so called VCR with capture built in showed quality. They looked bad. That VCR was summarily returned for money back and this was from USA.
Even I had card best one I can find, the chipset was claimed to be 10 bit resolution in the datahsheet, but was derated to 8 bit or less in software that was from the capture card handbook, and had noise in the PCB as herringbone pattern on the captured video.
This meant I had to strip off the tracks from the s-video input all the way to terminations network which is 3 inches away around the chipset, modified the network correctly and installed coax cables to make new connections from the input to there. This made herringbone pattern noise disappear but capture still have that poor resolution vs original video as viewed on good TV and on captured video on computer. This ended the experiment. And this was in around 2008 time and card was bought new.
Even the ATI theater chipset might not be best. Now we have choice of getting used commercial grade capture boxes with very little loss.
Cheers,
Great Northern aka Canada.