Escape 122 - Revision history

Multimedia Mike: samples link

2008-03-21T21:48:30Z

samples link

← Older revision		Revision as of 14:48, 21 March 2008
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	* Company: [[Eidos Technologies]]		* Company: [[Eidos Technologies]]
			* Samples: http://samples.mplayerhq.hu/game-formats/rpl/bigredracing-escape122/

	The ESCAPE 122 codec is a relatively simple 8-bit palettized video compression engine based on multipass [[BTC]] encoding and operates with 8x8 "superblocks" combined from 2x2 macroblocks.		The ESCAPE 122 codec is a relatively simple 8-bit palettized video compression engine based on multipass [[BTC]] encoding and operates with 8x8 "superblocks" combined from 2x2 macroblocks.

Multimedia Mike: remove invalid samples link (need samples for this format)

2008-03-21T15:34:22Z

remove invalid samples link (need samples for this format)

← Older revision		Revision as of 08:34, 21 March 2008
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	* Company: [[Eidos Technologies]]		* Company: [[Eidos Technologies]]
	* Samples: http://tranquillity.campus.luth.se/~banan/Escape/

	The ESCAPE 122 codec is a relatively simple 8-bit palettized video compression engine based on multipass [[BTC]] encoding and operates with 8x8 "superblocks" combined from 2x2 macroblocks.		The ESCAPE 122 codec is a relatively simple 8-bit palettized video compression engine based on multipass [[BTC]] encoding and operates with 8x8 "superblocks" combined from 2x2 macroblocks.

Multimedia Mike: make it a video codec as well

2008-03-20T22:33:16Z

make it a video codec as well

← Older revision		Revision as of 15:33, 20 March 2008
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	'''TODO: Insert IMA ADPCM description & link here'''		'''TODO: Insert IMA ADPCM description & link here'''

			[[Category:Video Codecs]]
	[[Category:Game Formats]]		[[Category:Game Formats]]

DonDiego: Add to Game Formats category.

2006-08-01T06:55:34Z

Add to Game Formats category.

← Older revision		Revision as of 23:55, 31 July 2006
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	'''TODO: Insert IMA ADPCM description & link here'''		'''TODO: Insert IMA ADPCM description & link here'''

			[[Category:Game Formats]]

DonDiego: Add standard company and samples links.

2006-07-03T10:43:01Z

Add standard company and samples links.

← Older revision		Revision as of 03:43, 3 July 2006
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	* ~~Sample files~~: http://tranquillity.campus.luth.se/~banan/Escape/		* Company: [[Eidos Technologies]]
			* Samples: http://tranquillity.campus.luth.se/~banan/Escape/

	The ESCAPE 122 codec is a relatively simple 8-bit palettized video compression engine based on multipass [[BTC]] encoding and operates with 8x8 "superblocks" combined from 2x2 macroblocks.		The ESCAPE 122 codec is a relatively simple 8-bit palettized video compression engine based on multipass [[BTC]] encoding and operates with 8x8 "superblocks" combined from 2x2 macroblocks.

DonDiego: a ton of grammar and spelling fixes

2006-06-30T02:41:24Z

a ton of grammar and spelling fixes

← Older revision		Revision as of 19:41, 29 June 2006
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	* Sample files: http://tranquillity.campus.luth.se/~banan/Escape/		* Sample files: http://tranquillity.campus.luth.se/~banan/Escape/

	The ESCAPE 122 codec is a relatively simple 8-bit ~~palletized~~ video compression engine based on multipass [[BTC]] encoding and operates with 8x8 "superblocks" combined from 2x2 macroblocks.		The ESCAPE 122 codec is a relatively simple 8-bit palettized video compression engine based on multipass [[BTC]] encoding and operates with 8x8 "superblocks" combined from 2x2 macroblocks.

	~~Packed~~ video stream usually stored within [[ARMovie]] container. Each frame chunk begins with 8-byte header (here and below all numbers are little-endian):		The packed video stream is usually stored within an [[ARMovie]] container. Each frame chunk begins with an 8-byte header (here and below all numbers are little-endian):

	dword video_size - size of the video portion		dword video_size - size of the video portion
	dword audio_size - size of the audio portion		dword audio_size - size of the audio portion

	Video data ~~started~~ immediately after this header and followed by audio data (if any).		Video data starts immediately after this header and is followed by audio data (if any).

	Note: ~~Existing~~ original decoder implementation only supports 320x200 video. Only one sample file encoded in this resolution is known so far.		Note: The existing original decoder implementation only supports 320x200 video. Only one sample file encoded in this resolution is known so far.

	== Video portion ==		== Video portion ==

	~~First~~ 2 bytes of the chunk ~~indicates~~ following palette block ~~length~~. Palette stored as standard VGA DAC B-G-R triplets and includes variable number of color entries, which can be ~~determinated~~ by dividing palette length by 3 and rounding result toward zero (thus, block length may not necessarily be a ~~multiply~~ of 3). Right after ~~pallete~~ block actual compressed frame data begins.		The first 2 bytes of the chunk indicate the length of the following palette block. Palette is stored as standard VGA DAC B-G-R triplets and includes a variable number of color entries, which can be determined by dividing palette length by 3 and rounding result toward zero (thus, block length may not necessarily be a multiple of 3). Right after the palette block the actual compressed frame data begins.

			The Video decoding algorithm operates as follows:
	Video decoding algorithm operates as follows:

	repeat		repeat
Line 61:		Line 60:

	read 2*2 (number of pixels in macroblock) mask bits from the stream		read 2*2 (number of pixels in macroblock) mask bits from the stream
	if all mask bits is set or clear		if all mask bits are set or clear
	read 7 top bits of color from the stream		read 7 top bits of color from the stream
	the lowest bit of color is the any bit of mask		the lowest bit of color is the any bit of mask

Merbanan: Added link to samples

2006-06-29T22:34:47Z

Added link to samples

← Older revision		Revision as of 15:34, 29 June 2006
Line 1:		Line 1:
			* Sample files: http://tranquillity.campus.luth.se/~banan/Escape/

	The ESCAPE 122 codec is a relatively simple 8-bit palletized video compression engine based on multipass [[BTC]] encoding and operates with 8x8 "superblocks" combined from 2x2 macroblocks.		The ESCAPE 122 codec is a relatively simple 8-bit palletized video compression engine based on multipass [[BTC]] encoding and operates with 8x8 "superblocks" combined from 2x2 macroblocks.

VAG at 19:31, 29 June 2006

2006-06-29T19:31:07Z

New page

The ESCAPE 122 codec is a relatively simple 8-bit palletized video compression engine based on multipass [[BTC]] encoding and operates with 8x8 "superblocks" combined from 2x2 macroblocks.

Packed video stream usually stored within [[ARMovie]] container. Each frame chunk begins with 8-byte header (here and below all numbers are little-endian):

dword video_size - size of the video portion
dword audio_size - size of the audio portion

Video data started immediately after this header and followed by audio data (if any).

Note: Existing original decoder implementation only supports 320x200 video. Only one sample file encoded in this resolution is known so far.

== Video portion ==

First 2 bytes of the chunk indicates following palette block length. Palette stored as standard VGA DAC B-G-R triplets and includes variable number of color entries, which can be determinated by dividing palette length by 3 and rounding result toward zero (thus, block length may not necessarily be a multiply of 3). Right after pallete block actual compressed frame data begins.

Video decoding algorithm operates as follows:

repeat
skip_value = RICE_Decode()
skip skip_value number of 8x8 superblocks (keep them unchanged from the last frame)

if all blocks drawn/skipped
finish

while next bit of the stream is zero
new_block = Decode_MacroBlock()
mask = read 4*4 (number of macroblocks in superblock) bits
for each macroblock of superblock (left to right, top to bottom)
if next bit of mask (from low to high) is set
macroblock = new_block

if next bit of the stream is zero
mask = read 4*4 (number of macroblocks in superblock) bits
for each macroblock of superblock (left to right, top to bottom)
if next bit of mask (from low to high) is set
macroblock = Decode_MacroBlock()

advance to the next superblock

The RICE_Decode performs RICE-like value unpacking and operates as follows:

value = 0
more_bits = read 1 bit from the stream
if 1 bit of more_bits is set
value = value + more_bits
more_bits = read 3 bits from the stream
value = value + more_bits
if 3 bits of more_bits is set
more_bits = read 7 bits from the stream
value = value + more_bits
if 7 bits of more_bits is set
more_bits = read 12 bits from the stream
value = value + more_bits

Decode_Macroblock performs 2x2 macroblock decoding:

read 2*2 (number of pixels in macroblock) mask bits from the stream
if all mask bits is set or clear
read 7 top bits of color from the stream
the lowest bit of color is the any bit of mask
fill whole macroblock with color
else
read 8 bits of color0 from the stream
read 8 bits of color1 from the stream
for each pixel of macroblock (left to right, top to bottom)
if next bit of mask (from low to high) is set
pixel = color1
else
pixel = color0

== Audio portion ==

'''TODO: Insert IMA ADPCM description & link here'''