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DumpVideoSignalEng.md

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PPUPlayer Video Dump Guide

Requirements:

First run of PPUPlayer

Start PPUPlayer:

dump_video_001

Select in the settings the PPU revision for which you want to get the video signal dump:

dump_video_002

Run PPUPlayer in "free flight" (Run PPU). Go to the Current Scan tab and make sure the PPU is alive:

dump_video_003

Dump of PPU state in Nintendulator

Run some game in Nintendulator, preferably without a complicated mapper.

Open the debugger and save all of the PPU memory:

dump_video_004

You will get a file with the extension .ppumem, which can be found somewhere in the depths of your Users/AppData folder.

Loading PPU state into the PPUPlayer

Select Load Nintendulator PPU Dump in the menu PPU Dumps and load the PPU memory dump from the Nintendulator.

This will result in something like this:

dump_video_005

But oops. Something's wrong.

The point is that the Nintendulator only saves the PPU memory, but not the current values of registers $2000 and $2001.

Especially important is register $2000, which sets the Pattern table addresses and sprite size.

To fix this, go to the Debug tab and change the value of register $2000 (for Contra you need to set it to 0x30):

dump_video_006

It turned out like this:

dump_video_007

Turn on the video signal dump

There is only one small thing left to do.

In the menu PPU Dumps you need to select Start video signal dump, specify the file and then the dump to the video output file of the PPU chip will start automatically.

  • For "composite" PPU (2C02/2C07) we dump a float array, each value represents a voltage (signal level)
  • For RGB PPU 4 bytes are dumped (in order R, G, B, SYNC) which correspond to RGB PPU outputs

RAW Dump

It is possible to get the pixel value before the DAC circuitry instead of the PPU video signal:

dump_video_008

In this case uint16_t values of the following format will be dumped:

		/// <summary>
		/// Raw PPU color, which is obtained from the PPU circuits BEFORE the video signal generator.
		/// The user can switch the PPUSim video output to use "raw" color, instead of the original (Composite/RGB).
		/// </summary>
		union RAWOut
		{
			struct
			{
				unsigned CC0 : 1;	// Chroma (CB[0-3])
				unsigned CC1 : 1;
				unsigned CC2 : 1;
				unsigned CC3 : 1;
				unsigned LL0 : 1;	// Luma (CB[4-5])
				unsigned LL1 : 1;
				unsigned TR : 1;	// "Tint Red", $2001[5]
				unsigned TG : 1;	// "Tint Green", $2001[6]
				unsigned TB : 1;	// "Tint Blue", $2001[7]
				unsigned Sync : 1;	// 1: Sync level
			};
			uint16_t raw;
		} RAW;

Summary

PPUPlayer has become a powerful tool in exploring PPU. There is a real live PPU living inside of it.

Feel free to push the different buttons in PPUPlayer and experiment. If anything, there is also a presentation (nearby).