Yaz (File Compression) - Revision history

Mzxrules at 00:33, 13 February 2019

2019-02-13T00:33:55Z

Mzxrules: bleh, writing

2015-06-03T00:50:26Z

bleh, writing

Mzxrules: Mzxrules moved page Yaz to Yaz (File Compression)

2015-06-03T00:40:13Z

Mzxrules moved page Yaz to Yaz (File Compression)

Mzxrules: Mzxrules moved page Yaz0 to Yaz: in 64DD games the '0' and '1' in Ya* and MIO are read to determine if the archive source is cart of disk respectively

2015-06-03T00:39:46Z

Mzxrules moved page Yaz0 to Yaz: in 64DD games the '0' and '1' in Ya* and MIO are read to determine if the archive source is cart of disk respectively

Mzxrules: 1 revision

2014-06-08T23:21:13Z

1 revision

Mzxrules at 01:57, 8 March 2014

2014-03-08T01:57:58Z

New page

Yaz0 is the file compression algorithm used in Ocarina of Time and other Nintendo games.

More info about the Yaz0 algorithm can be found at [http://www.amnoid.de/gc/yaz0.txt] and source code for compressing/decompressing Yaz0 blocks can be found at [http://www.amnoid.de/gc/index.html]

[[Category:Documentation]]

← Older revision		Revision as of 00:33, 13 February 2019
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	In 64DD games the '0' and '1' in Yay, Yaz and MIO are read to determine if the archive source is cart or disk respectively. However, due to the lack of Disk Drive games, and emulators capable of supporting them, Yaz is often called Yaz0.		In 64DD games the '0' and '1' in Yay, Yaz and MIO are read to determine if the archive source is cart or disk respectively. However, due to the lack of Disk Drive games, and emulators capable of supporting them, Yaz is often called Yaz0.
		+
		+	== Algorithm ==
		+
		+	=== Header ===
		+
		+	The first 0x10 bytes are reserved for the header.
		+
		+	{\|class="wikitable"
		+	! Offset \|\| End \|\| Data
		+	\|-
		+	\| 0000 \|\| 0003 \|\| Ascii string 'Yaz'
		+	\|-
		+	\| 0003 \|\| 0004 \|\| Ascii string '0' or '1'
		+	\|-
		+	\| 0004 \|\| 0008 \|\| int Decompressed Size
		+	\|-
		+	\| 0008 \|\| 0010 \|\| Padding
		+	\|}
		+
		+	=== Decoding Data ===
		+
		+	The Yaz data field is split up into variable sized chunks containing a maximum of 25 bytes per chunk.
		+
		+	The first byte in a chunk acts as a "code" byte. Starting with the most significant bit, each bit determines whether the next data should be copied directly to the file stream, or contains a special "copy from decoded file stream" encoding that is either 2 or 3 bytes long.
		+
		+	* If the next bit is 1, the next byte in the chunk is copied to the file stream, and the chunk and file stream cursors are incremented
		+	* If the next bit is 0, the next two bytes in the chunk are read, and the chunk cursor is incremented by 2.
		+
		+	The first two bytes of the encoding store the following variables:
		+
		+	* <tt>seekback = (encode & 0x0FFF) + 1</tt>
		+	* <tt>n = encode & 0xF000</tt> stores the number of bytes to copy.
		+
		+	<tt>seekback</tt> is the number of bytes to seek backwards from the file stream's current position to begin the copy.
		+
		+	<tt>n</tt> determines the number of bytes to copy:
		+
		+	* If n > 0, then the number of bytes to copy is n + 2, giving you a minimum of 3 and maximum of 0x11 bytes encoded.
		+	* If n == 0, then the next byte in the chunk is read and stored in n. The number of bytes to copy is n + 0x12, or a maximum of 0xFF + 0x12 bytes encoded

	[[Category:Documentation]]		[[Category:Documentation]]

@@ Line 1: / Line 1: @@
-Yaz0 is the file compression algorithm used in Ocarina of Time and other Nintendo games.
+Yaz is the file compression algorithm used in Ocarina of Time and other Nintendo games.
-More info about the Yaz0 algorithm can be found at [http://www.amnoid.de/gc/yaz0.txt] and source code for compressing/decompressing Yaz0 blocks can be found at [http://www.amnoid.de/gc/index.html]
+More info about the Yaz algorithm can be found at [http://www.amnoid.de/gc/yaz0.txt] and source code for compressing/decompressing Yaz blocks can be found at [http://www.amnoid.de/gc/index.html]
 [[Category:Documentation]]

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