nesdev.org

Actually, if you go to Layers->Colors->Colorcube Analysis, you can see the number of different colors in any image, whether the image is 8-bit or not. I just tested it with a photo that has about 25000 different colors. This is in version 2.2.10, so it may have been moved to a different menu in newe...

On the Famicom, extended sound is generated by passing the standard audio output throught the cart, where the extended channels are mixed in by the cartridge's hardware. This means that a separate mixing algorithm might be necessary for each type of extended hardware - one algorithm for MMC5 boards...

Blargg's algorithms are great for mixing the standard five sound channels. But it recently occurred to me that there is likely to be an inherent challenge in devising an actual mixing algorithm for extended sound. On the Famicom, extended sound is generated by passing the standard audio output throu...

blargg: <i>Without extra equipment it's a bit hard to measure the frequency response of the post-APU circuitry, since a PC's digitizer has its own frequency response that gets in the way if you simply try to digitize the output. </i> Couldn't someone familiar with audio filtering figure it out from ...

Yeah, it was pretty much the band-pass filter I was referring to. Blargg did a good job of documenting the mixing ratios, and obviously the amplification will be handled by the sound hardware. But there is almost certainly some kind of analog filter in the circuit that affects audible frequencies, a...

Recently, there has been a great deal of progress towards accurate video filtering, especially now that Blargg's NTSC video filters have found their way into many emulators. But what about audio? Most emulators just do a simple averaging of samples (if they even sample at the full NES CPU clock rate...

Wouldn't the best solution be to make the Cart DB part of the NESDev Wiki? That way, anyone who wants to could contribute.

n6: " Is VBlank flag cleared as well in the start of each frame? I also have some annoying bug in the PPU that makes Super Mario Bros don't give correct output, Maybe its possible for you to see what the problem is... " I had a similar problem in a PPU engine I wrote a while back. The prob...

Wouldn't it cause a glitch in the sound output if the DPCM DMA was delayed?

What happens if you perform an OAM DMA via $4014, and during the middle of the 513-cycle period when the DMA is happening, the DPCM channel needs to load the next sample byte? Does the OAM DMA simply get interrupted for the DPCM DMA event, and then resumed where it left off? Also, DPCM DMA is said t...

So, it sounds like multi-byte NOPs should probably be implemented even if you aren't going to do the full undocumented opcode set. They are far more likely to be used, and are included in at least one licensed game if the above info is correct. Besides, they're very easy to add.

Yes, and the original 2A03 CPU does indeed support various undocumented opcodes. Nothing is being "created". My point is that some Game Genie codes may change game behavior by altering a documented opcode byte into an undocumented opcode byte.

Another thing to consider is that some Game Genie codes may work by creating an undocumented opcode.

However, some commercial games do rely on this behavior. For instance, if you don't support mid-scanline alterations to PPU registers and/or CHR bank registers, Marble Madness, Pirates!, and Mother will all exhibit various levels of graphical corruption. Also, the orb-relighting beam on Final Fantas...

Not sure if this is of any help to Blargg, but I devised MMX versions of two pixel processing algorithms he described on his website. The first was for averaging two 15-bit RGB pixels ( http://www.slack.net/~ant/info/rgb_mixing.html ). Here's the MMX equivalent I came up with to Blargg's C code, whi...