If we want to talk about digital Genesis video, it'd be great to do that. A pixel bus snooping solution would be difficult, but not impossible.
VDP register $0C bit %00010000 enables the 8-bit pixel bus output. This bus gives us a 6-bit index into the color ram (CRAM), as well as shadow/highlight status. This is similar to the EXT bus on the 2C02 PPU, except we don't have to do any intercepts to infer a missing fifth bit.
The problem is snooping palette writes. Capturing writes done with simple CPU-->VDP writes are not hard. Many games use DMA to transfer colors, though, so the challenge becomes complicated. We must snoop writes to the VDP to 1) determine that a DMA to CRAM is being set up, 2) recognize that the DMA has begun, and 3) accurately capture palette data being written during DMA.
CRAM is internal to the VDP, otherwise this would be extremely easy. Since it's not accessible, a cycle-accurate DMA controller must be replicated, and what other internal state of the VDP it relies on is unknown to me. That is the challenging bit.
tepples wrote:
HDMI improves compatibility with TVs purchased in the past decade.
In addition, it doesn't look like dogshit.