LOCO - Revision history

Multimedia Mike: link to mirrored file

2022-04-11T05:27:45Z

link to mirrored file

← Older revision		Revision as of 22:27, 10 April 2022
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	More information on LOCO-I can be found on:		More information on LOCO-I can be found on:
	* [http://www.jpeg.org/public/fcd14495p.pdf FCD14495] (JPEG-LS final comittee draft)		* [http://www.jpeg.org/public/fcd14495p.pdf FCD14495] ([[Mirrored Files\|Mirrored]]) (JPEG-LS final comittee draft)
	* [http://www.hpl.hp.com/loco/ http://www.hpl.hp.com/loco/] (LOCO-I description)		* [http://www.hpl.hp.com/loco/ http://www.hpl.hp.com/loco/] (LOCO-I description)

DonDiego: linkify JPEG-LS, grammar

2006-11-12T11:52:33Z

linkify JPEG-LS, grammar

← Older revision		Revision as of 04:52, 12 November 2006
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	* Samples: [http://samples.mplayerhq.hu/V-codecs/LOCO/ http://samples.mplayerhq.hu/V-codecs/LOCO/]		* Samples: [http://samples.mplayerhq.hu/V-codecs/LOCO/ http://samples.mplayerhq.hu/V-codecs/LOCO/]

	LOCO codec written by Mohammad Rezaei and based on JPEG-LS lossy/lossless compression scheme, originally known as LOCO-I.		LOCO codec written by Mohammad Rezaei and based on the [[JPEG-LS]] lossy/lossless compression scheme, originally known as LOCO-I.

	More information on LOCO-I can be found on:		More information on LOCO-I can be found on:

Dashcloud: Update samples link

2006-08-18T00:58:24Z

Update samples link

← Older revision		Revision as of 17:58, 17 August 2006
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	* FourCC: LOCO		* FourCC: LOCO
	* Samples: [http://~~www~~.mplayerhq.hu~~/MPlayer/samples~~/V-codecs/LOCO/ http://~~www~~.mplayerhq.hu~~/MPlayer/samples~~/V-codecs/LOCO/]		* Samples: [http://samples.mplayerhq.hu/V-codecs/LOCO/ http://samples.mplayerhq.hu/V-codecs/LOCO/]

	LOCO codec written by Mohammad Rezaei and based on JPEG-LS lossy/lossless compression scheme, originally known as LOCO-I.		LOCO codec written by Mohammad Rezaei and based on JPEG-LS lossy/lossless compression scheme, originally known as LOCO-I.

Multimedia Mike: /* Prediction */ English edits

2006-05-06T18:55:34Z

Prediction: English edits

← Older revision		Revision as of 11:55, 6 May 2006
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	== Prediction ==		== Prediction ==

	~~if we predict~~ pixel X ~~we use such context~~:		A pixel (X) can predict from up to 3 surrounding pixels: up (A), left (B), and up-left (C):

	+---+---+		+---+---+
Line 25:		Line 25:
	+---+---+		+---+---+

	~~There are four cases~~:		The prediction logic works as follows:
	* A,B,C are unavailable (X is top left pixel) - use 128 as prediction value		* A,B,C are unavailable (X is top left pixel) - use 128 as prediction value
	* A and C are unavailable (X is in the top line) - use B as predictor		* A and C are unavailable (X is in the top line) - use B as predictor
	* B and C are unavailable (X is in the first column) - use A as predictor		* B and C are unavailable (X is in the first column) - use A as predictor
	* A,B,C are available (this one is JPEG-LS prediction scheme):		* A,B,C are available (this one is the JPEG-LS prediction scheme):
	** if C >= max(A,B) then use min(A,B) as predictor		** if C >= max(A,B) then use min(A,B) as predictor
	** if C <= min(A,B) then use max(A,B) as predictor		** if C <= min(A,B) then use max(A,B) as predictor
	** else use (A+B-C) as predictor		** else use (A+B-C) as predictor

	== Residue Decoding ==		== Residue Decoding ==

Multimedia Mike: categorize FourCC

2006-04-21T02:37:33Z

categorize FourCC

← Older revision		Revision as of 19:37, 20 April 2006
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	[[Category:Video Codecs]]		[[Category:Video Codecs]]
			[[Category:Video FourCCs]]

Multimedia Mike: revert spam/vandalism

2006-03-24T19:01:50Z

revert spam/vandalism

@@ Line 9: / Line 9: @@
 * [http://www.jpeg.org/public/fcd14495p.pdf FCD14495] (JPEG-LS final comittee draft)
 * [http://www.hpl.hp.com/loco/ http://www.hpl.hp.com/loco/] (LOCO-I description)
 == Decoding Process ==

70.33.25.195: "

2006-03-24T04:59:56Z

@@ Line 9: / Line 9: @@
 * [http://www.jpeg.org/public/fcd14495p.pdf FCD14495] (JPEG-LS final comittee draft)
 * [http://www.hpl.hp.com/loco/ http://www.hpl.hp.com/loco/] (LOCO-I description)
 == Decoding Process ==

Multimedia Mike: sample link

2006-03-17T06:50:32Z

sample link

← Older revision		Revision as of 23:50, 16 March 2006
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	''This page is originally based on a description written by [[User:Kostya]].''		''This page is originally based on a description written by [[User:Kostya]].''

	* ~~FOURCC~~: LOCO		* FourCC: LOCO
			* Samples: [http://www.mplayerhq.hu/MPlayer/samples/V-codecs/LOCO/ http://www.mplayerhq.hu/MPlayer/samples/V-codecs/LOCO/]

	LOCO codec written by Mohammad Rezaei and based on JPEG-LS lossy/lossless compression scheme, originally known as LOCO-I.		LOCO codec written by Mohammad Rezaei and based on JPEG-LS lossy/lossless compression scheme, originally known as LOCO-I.

Kostya: Fixed link on FCD

2006-02-06T04:34:22Z

Fixed link on FCD

← Older revision		Revision as of 21:34, 5 February 2006
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	More information on LOCO-I can be found on:		More information on LOCO-I can be found on:
	* ~~fcd14495p~~.~~pdf at~~ jpeg.org (JPEG-LS final comittee draft)		* [http://www.jpeg.org/public/fcd14495p.pdf FCD14495] (JPEG-LS final comittee draft)
	* [http://www.hpl.hp.com/loco/ http://www.hpl.hp.com/loco/] (LOCO-I description)		* [http://www.hpl.hp.com/loco/ http://www.hpl.hp.com/loco/] (LOCO-I description)

Multimedia Mike at 19:03, 5 February 2006

2006-02-05T19:03:05Z

New page

''This page is originally based on a description written by [[User:Kostya]].''

* FOURCC: LOCO

LOCO codec written by Mohammad Rezaei and based on JPEG-LS lossy/lossless compression scheme, originally known as LOCO-I.

More information on LOCO-I can be found on:
* fcd14495p.pdf at jpeg.org (JPEG-LS final comittee draft)
* [http://www.hpl.hp.com/loco/ http://www.hpl.hp.com/loco/] (LOCO-I description)

== Decoding Process ==
# get predictor
# decode residue
# output predictor minus residue as new pixel

== Prediction ==

if we predict pixel X we use such context:

+---+---+
| C | A |
+---+---+
| B | X |
+---+---+

There are four cases:
* A,B,C are unavailable (X is top left pixel) - use 128 as prediction value
* A and C are unavailable (X is in the top line) - use B as predictor
* B and C are unavailable (X is in the first column) - use A as predictor
* A,B,C are available (this one is JPEG-LS prediction scheme):
** if C >= max(A,B) then use min(A,B) as predictor
** if C <= min(A,B) then use max(A,B) as predictor
** else use (A+B-C) as predictor

== Residue Decoding ==

Residue decoding is based on Rice codes. There are some differences though:
* Numbers are stored as their absolute value in Rice code and one trailing bit shows their sign - 0 for positive, 1 for negative integers
* Rice parameter is not static but updates every time
If there is lossy compression mode, then add loss value:
if(val > 0)val += loss
if(val < 0)val -= loss

== Rice Code Decoding ==

* Get standard Rice code with given parameter
* It new code is zero
** If we have some saved bits:
*** Get Rice(2) code meaning run length of zeroes
*** If run length is more than one then add (run_length + 1) bits to saved bit, else substract 3 from saved bits
** Else increment decode_run_length
* If new code is non-zero:
** If decode_run_length > 2 then add it to saved bits, else substract 3 from saved bits
** Set decode_run_length to zero
* Return new code

== Rice Code Parameter Updating ==

Rice decoder choses its parameter based on two things - sum of absolute values of decoded residues and their number. To avoid overflow if count went up to sixteen then halve both count and sum.

Rice parameter is log2(sum/number) clamped to interval [0..9]

[[Category:Video Codecs]]