Famicom World

Family Computer => Famicom / Disk System => Topic started by: 133MHz on January 22, 2009, 07:51:30 pm

Title: Why is the Famicom's video output shifted one tile to the right?
Post by: 133MHz on January 22, 2009, 07:51:30 pm
Does somebody know the technical and/or historical reason(s) for this? It always bugged me out and made me think that my TV set was misaligned. Could we classify this as one of the Famicom's mysteries? :P
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: nintendodork on January 22, 2009, 07:52:44 pm
Does it happen even when you use an R/F Famicom?  It could also just be your TV..on some games in some parts, there's always a BG colored "frame" on the sides of some games on my 20'' flat screen I have in my room..
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: 133MHz on January 22, 2009, 07:57:01 pm
It happens on the Famicom (RF or AV doesn't matter), on the NES, Famiclones, etc.
What you describe is that you're looking around the overscan area that's not usually displayed by a standard CRT TV set, usually the background color leaked into those areas (and sometimes garbage scrolling/sprite data) because it wasn't meant to be seen anyway.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: nintendodork on January 22, 2009, 08:00:18 pm
Thanks for answering that!  I was always wondering what that meant.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: Trium Shockwave on January 22, 2009, 08:48:29 pm
Maybe they were using that "unseen" area of video to preload some sprite data into the PPU's cache? That's all I can come up with.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: UglyJoe on January 22, 2009, 08:57:17 pm
Quote from: Trium Shockwave on January 22, 2009, 08:48:29 pm
Maybe they were using that "unseen" area of video to preload some sprite data into the PPU's cache? That's all I can come up with.


Nah.  The data loaded into the PPU can just sit in the PPU memory.  It doesn't need to be on screen.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: L___E___T on January 23, 2009, 08:43:29 am
It doesn't happen on Wii :D 

but I guess that's besides the point.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: nintendodork on January 23, 2009, 10:00:20 am
That's 'cause the Wii isn't over 20 years old :D  It was made for present day TVs
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: 133MHz on January 23, 2009, 10:07:47 am
I think he's referring to an accurate emulation standpoint.
For an emulator to be 100% accurate, the same behavior should be recreated.

Something a little OT: Did you know that the Wii Virtual Console NES games use iNES headers?! :o
What a bunch of hypocrites >:(
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: NintendoKing on January 23, 2009, 10:08:58 am
Modern Televisions are wider then televisions in the 1980's so the system is unable to compensate which causes extra area around the sides.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: UglyJoe on January 23, 2009, 10:13:43 am
Quote from: 133MHz on January 23, 2009, 10:07:47 am
Something a little OT: Did you know that the Wii Virtual Console NES games use iNES headers?! :o


If the roms didn't have a header, the emulator would have no way of knowing which mapper it needs to emulate.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: nintendodork on January 23, 2009, 10:17:35 am
So then where did they get the header for use in the NES back in the day?
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: 133MHz on January 23, 2009, 10:18:51 am
Quote from: UglyJoe on January 23, 2009, 10:13:43 am
If the roms didn't have a header, the emulator would have no way of knowing which mapper it needs to emulate.


But such a HUEG company like Nintendo should have more than enough resources to invent a system themselves, aren't they the ones with access to the whole FC/NES documentation and the source code to many of the games?

It bugs me out because they're heavily against emulation and homebrew, but at the same time they're using a system invented by the very same people they're trying to crack down >:(

Quote from: nintendodork on January 23, 2009, 10:17:35 am
So then where did they get the header for use in the NES back in the day?


A real FC/NES console does not need a header to run a cartridge. It just works.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: UglyJoe on January 23, 2009, 10:22:21 am
Quote from: nintendodork on January 23, 2009, 10:17:35 am
So then where did they get the header for use in the NES back in the day?


Mappers work by writing values to hadware-specific registers.  The game's code assumes the mappers is present.  In the case of an NES cart, the mapper is of course there, so it works.  When you dump a ROM from a cart, all you get is the code and graphics (PRG and CHR).  There's nothing in the code that says "I use this mapper"*.  So, if the emulator just runs the code, the writes to those registers go unnoticed.  You need the header to tell the emulator which mapper (if any) to use so that those registers actually do something.

* If you look at the code, you might be able to guess based on what non-standard registers are being written to, but this method is unreliable for a number of reasons.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: nintendodork on January 23, 2009, 10:22:31 am
Do the creators of iNES know Nintendo is using their emu?
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: UglyJoe on January 23, 2009, 10:23:20 am
Quote from: nintendodork on January 23, 2009, 10:22:31 am
Do the creators of iNES know Nintendo is using their emu?


iNES is a header format created by (illegal) cart dumper manufacturers.  It's not an emulator.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: nintendodork on January 23, 2009, 10:24:58 am
Well, I guess, that's what I meant...
Do they know that Nintendo is using iNES?
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: UglyJoe on January 23, 2009, 10:25:38 am
For all intents and purposes, there is no "they".

edit: Okay, I guess "they" is Marat Fayzullin (http://fms.komkon.org/ (http://fms.komkon.org/)).  If he cares to know about it, I'm sure he does by now.  Also, apparently iNES is an emulator as well.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: 133MHz on January 23, 2009, 10:30:48 am
As a side note, speaking of NES emulation accuracy on the Wii, L___E___T posted that the "video shifted one tile to the right" behavior doesn't happen on the Wii, that means it's not 100% accurate and true to the original hardware anymore, and also I remembered that the Wii VC version of SMB3 doesn't have the status bar glitch present on the original version: either the emulation is compensating for it (making it not-100% accurate again) or Nintendo simply fixed the glitch in the original game (having the source code).
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: 133MHz on January 23, 2009, 10:38:28 am
Quote from: UglyJoe on January 23, 2009, 10:25:38 am
edit: Okay, I guess "they" is Marat Fayzullin (http://fms.komkon.org/ (http://fms.komkon.org/)).  If he cares to know about it, I'm sure he does by now.  Also, apparently iNES is an emulator as well.


Yeah I wanted to remark that, but I didn't wanna get pedantic and we all knew what nintendodork was referring about :P.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: nintendodork on January 23, 2009, 10:44:55 am
I was gonna say, I was almost positive iNES was an emulator, but if iNES was my creation, and I didn't know Nintendo was using it, I would demand money :P
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: UglyJoe on January 23, 2009, 10:47:20 am
Well, they're only using the header format he came up with.  Going after Nintendo for using a 16-byte header of your own creation would be a very difficult feat.
Title: Re: Why is the Famicom's video output shifted one tile to the right?
Post by: Josh on January 24, 2009, 06:15:20 pm
Reading the history of the iNES emulator's development here was interesting:

http://fms.komkon.org/iNES/

It was only the second NES emulator ever after Pasofami, it was the first to use the .NES file format (and therefore iNES headers, right?), and was released in 1996 ... for $20.  And if you want it today, you still have to pay for it. :D :D :D

Quote from: 133MHz on January 23, 2009, 10:30:48 am
As a side note, speaking of NES emulation accuracy on the Wii, L___E___T posted that the "video shifted one tile to the right" behavior doesn't happen on the Wii, that means it's not 100% accurate and true to the original hardware anymore, and also I remembered that the Wii VC version of SMB3 doesn't have the status bar glitch present on the original version: either the emulation is compensating for it (making it not-100% accurate again) or Nintendo simply fixed the glitch in the original game (having the source code).


OK, what is this "video shifted one tile to the right" issue/characteristic you're talking about?  You never explained it in this thread...

And regarding Nintendo's Virtual Console emulators, I highly doubt they went back and modified the source code for SMB3.  Making an inaccurate emulator is probably the easier option (and we already know they did that, don't we?).