Dirac - Revision history

R1: replaced obsoleted summary, dirac is now stable

2013-01-28T13:47:11Z

replaced obsoleted summary, dirac is now stable

← Older revision		Revision as of 06:47, 28 January 2013
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	* Samples: [http://samples.libav.org/V-codecs/Dirac/ Libav Samples] [http://diracvideo.org/download/test-streams/raw/ DiracVideo Samples]		* Samples: [http://samples.libav.org/V-codecs/Dirac/ Libav Samples] [http://diracvideo.org/download/test-streams/raw/ DiracVideo Samples]

	~~Experimental wavelet~~-based video codec ~~being~~ developed by the [[BBC]]. The development of a C++ Dirac implementation under the MPL license called libdirac is hosted at SourceForge.		Wavelet-based video codec developed by the [[BBC]]. The development of a C++ Dirac implementation under the MPL license called libdirac is hosted at SourceForge.
	[http://schrodinger.sf.net The Schrödinger Project] is an implementation written in ANSI C89, jointly developed by [[Fluendo]] and [[BBC]].		[http://schrodinger.sf.net The Schrödinger Project] is an implementation written in ANSI C89, jointly developed by [[Fluendo]] and [[BBC]].

	~~A Dirac decoder and encoder~~ has ~~been developed as part~~ of [[FFmpeg ~~Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer~~ of ~~Code 2007]] but has not yet been committed~~.		The Schroedinger C implementation has surpassed the quality of the original C++ libdirac one.

			FFmpeg supports both encoding and decoding via libschroedinger.

			Dirac performance is in the same range as MPEG4 or Theora (quite possibly better for high bitrates) but it is unfortunately much more CPU-intensive. The compression artifacts look different in Dirac compared to the DCT-based codecs, thus a preference may be a matter of personal taste.

	== About Wavelets ==		== About Wavelets ==
	Continuous Wavelet Transform (CWT) is an alternative to the Windowed Fourier Transform (WFT). The data analysis at different factor or resolutions is the main difference between CWT and WFT, also called multi-resolution analysis (MRA) which is also the justification for the algorithm of the Fast Wavelet Transform (FWT). In front of Fourier Transform which has only the sin() and cs() functions available, the Wavelet transform has infinite available functions, with that property the access to the information is immediate. The WFT projects a time function (the signal) into a A and B function, where A is known as scale and B is known as translation. A and B are also known as 'mother wavelet' and 'child wavelets'. A and B could be Quadrature Mirror Filter (QMF).		Continuous Wavelet Transform (CWT) is an alternative to the Windowed Fourier Transform (WFT). The data analysis at different factor or resolutions is the main difference between CWT and WFT, also called multi-resolution analysis (MRA) which is also the justification for the algorithm of the Fast Wavelet Transform (FWT). '''['''In front of Fourier Transform which has only the sin() and cos() functions available, the Wavelet transform has infinite available functions, with that property the access to the information is immediate. -- an odd-looking statement? -- Rl''']''' The WFT projects a time function (the signal) into a A and B function, where A is known as scale and B is known as translation. A and B are also known as 'mother wavelet' and 'child wavelets'. A and B could be Quadrature Mirror Filter (QMF).

	The Fast Wavelet Transform is designed to turn a waveform in the time domain into a sequence of coefficients based on an orthogonal basis of small finite waves or wavelets. The transform can be easily extended from time to other domains like images (2D-WT) or videos (3D-WT).		The Fast Wavelet Transform is designed to turn a waveform in the time domain into a sequence of coefficients based on an orthogonal basis of small finite waves or wavelets. The transform can be easily extended from time to other domains like images (2D-WT) or videos (3D-WT).

Ce: Dirac is no longer a missing format

2011-10-31T01:45:01Z

Dirac is no longer a missing format

← Older revision		Revision as of 18:45, 30 October 2011
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	[[Category: Video Codecs]]		[[Category: Video Codecs]]
	[[Category: Wavelet Video Codecs]]		[[Category: Wavelet Video Codecs]]
	~~[[Category: Formats missing in FFmpeg]]~~

Nenjordi: /* About Wavelets */

2011-08-19T17:26:05Z

About Wavelets

← Older revision		Revision as of 10:26, 19 August 2011
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	The Fast Wavelet Transform is designed to turn a waveform in the time domain into a sequence of coefficients based on an orthogonal basis of small finite waves or wavelets. The transform can be easily extended from time to other domains like images (2D-WT) or videos (3D-WT).		The Fast Wavelet Transform is designed to turn a waveform in the time domain into a sequence of coefficients based on an orthogonal basis of small finite waves or wavelets. The transform can be easily extended from time to other domains like images (2D-WT) or videos (3D-WT).

	For 1D-WT, applying two QMF Filters H ~~and G~~ would split the original signal into two halves, the low-pass (H) subband (or reference signal) and the high-pass (G) subband (or signal detail). In case of 2D-WT (e.g. Pictures), the FWT is applied to each row and each column generating four sub-bands: low-low (HH), high-low (GH), low-high (HG), high-high (GG). Each subband would contain respectively the following: a reference Picture of the original, the horizontal details, the vertical details, the diagonal details. Each subband is a quarter from the original size. 3D-WT follows the same principle of 2D-WT but generating nine subband. The transform can be applied as many times as it is desired, this is called iterations, the number of iterations isn't limited, that's why there is no limitations of size for the wavelet transform.		For 1D-WT, applying two QMF Filters L and H would split the original signal into two halves, the low-pass (L) subband (or reference signal) and the high-pass (H) subband (or signal detail). In case of 2D-WT (e.g. Pictures), the FWT is applied to each row and each column generating four sub-bands: low-low (LL), high-low (HL), low-high (LH), high-high (HH). Each subband would contain respectively the following: a reference Picture of the original, the horizontal details, the vertical details, the diagonal details. Each subband is a quarter from the original size. 3D-WT follows the same principle of 2D-WT but generating nine subband. The transform can be applied as many times as it is desired, this is called iterations, the number of iterations isn't limited, that's why there is no limitations of size for the wavelet transform.

	== Dirac Video Codec ==		== Dirac Video Codec ==
	Is an experimental wavelet-based video codec being developed by the BBC. The development of a C++ Dirac implementation under MPL license called libdirac is hosted at SourceForge. The Schröedinger project is an implementation written in ANSI C89, jointly developed by Fluendo and BBC. Libdirac is considered obsolete and the usage of libschroedinger is suggested.		Is an experimental wavelet-based video codec being developed by the BBC. The development of a C++ Dirac implementation under MPL license called libdirac is hosted at SourceForge. The Schröedinger project is an implementation written in ANSI C89, jointly developed by Fluendo and BBC. Libdirac is considered obsolete and the usage of libschroedinger is suggested.

Nenjordi: /* Dirac Video Codec */

2011-08-19T14:32:30Z

Dirac Video Codec

← Older revision		Revision as of 07:32, 19 August 2011
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	== Dirac Video Codec ==		== Dirac Video Codec ==
	Is an experimental wavelet-based video codec being developed by the BBC. The development of a C++ Dirac implementation under MPL license called libdirac is hosted at SourceForge. The Schröedinger project is an implementation written in ANSI C89, jointly developed by Fluendo and BBC. Libdirac is considered obsolete and the usage of libschroedinger is suggested.		Is an experimental wavelet-based video codec being developed by the BBC. The development of a C++ Dirac implementation under MPL license called libdirac is hosted at SourceForge. The Schröedinger project is an implementation written in ANSI C89, jointly developed by Fluendo and BBC. Libdirac is considered obsolete and the usage of libschroedinger is suggested.

			The structure of a Dirac decoder is similar to a well known block oriented codecs but where one would find a DCT/IDCT (Discrete Cosine Transform) a DWT/IDWT (Discrete Wavelet Transform) is found. Different wavelet filters are available for the DWT/IDWT step. Arithmetic coding was selected to provide a better bitstream compression.

			Dirac uses Overlapped Block Motion Compensation (OBMC) reducing the block artifacts with bigger block sizes. OBMC overlapps blocks making a pixel belong to more than a block. In addition motion compensation precission can afford from full pixel (fpel) until eighth pixel (epel).

	A dirac decoder and encoder was developed as part of FFmpeg's Summer of Code 2007. Refinements to that implementation will be carried out during the present Libav's Summer of Code 2011.		A dirac decoder and encoder was developed as part of FFmpeg's Summer of Code 2007. Refinements to that implementation will be carried out during the present Libav's Summer of Code 2011.

Lu zero at 10:08, 2 August 2011

2011-08-02T10:08:59Z

← Older revision		Revision as of 03:08, 2 August 2011
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	A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.		A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.

	~~{{TOCright}}~~

	== About Wavelets ==		== About Wavelets ==

Lu zero at 10:06, 2 August 2011

2011-08-02T10:06:55Z

← Older revision		Revision as of 03:06, 2 August 2011
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	A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.		A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.

	{{~~TOC~~}}		{{TOCright}}

	== About Wavelets ==		== About Wavelets ==

Lu zero at 10:05, 2 August 2011

2011-08-02T10:05:15Z

← Older revision		Revision as of 03:05, 2 August 2011
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	A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.		A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.

	~~__TOC__~~		{{TOC}}

	== About Wavelets ==		== About Wavelets ==

Lu zero at 10:03, 2 August 2011

2011-08-02T10:03:12Z

← Older revision		Revision as of 03:03, 2 August 2011
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	A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.		A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.

	~~{{TOC right}}~~		__TOC__

	== About Wavelets ==		== About Wavelets ==

Lu zero at 09:58, 2 August 2011

2011-08-02T09:58:58Z

← Older revision		Revision as of 02:58, 2 August 2011
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	A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.		A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.

			{{TOC right}}

	== About Wavelets ==		== About Wavelets ==

Lu zero at 09:56, 2 August 2011

2011-08-02T09:56:46Z

← Older revision		Revision as of 02:56, 2 August 2011
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			* FOURCC: BBCD
			* Company: [[BBC]]
			* Website: [http://diracvideo.org/ http://diracvideo.org]
			* Samples: [http://samples.libav.org/V-codecs/Dirac/ Libav Samples] [http://diracvideo.org/download/test-streams/raw/ DiracVideo Samples]

	Experimental wavelet-based video codec being developed by the [[BBC]]. The development of a C++ Dirac implementation under the MPL license called libdirac is hosted at SourceForge.		Experimental wavelet-based video codec being developed by the [[BBC]]. The development of a C++ Dirac implementation under the MPL license called libdirac is hosted at SourceForge.
	[http://schrodinger.sf.net The Schrödinger Project] is an implementation written in ANSI C89, jointly developed by [[Fluendo]] and [[BBC]].		[http://schrodinger.sf.net The Schrödinger Project] is an implementation written in ANSI C89, jointly developed by [[Fluendo]] and [[BBC]].
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	A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.		A Dirac decoder and encoder has been developed as part of [[FFmpeg Summer Of Code#Dirac_Encoder_and_Decoder\|FFmpeg's Summer of Code 2007]] but has not yet been committed.

	* FOURCC: BBCD
	* Company: [[BBC]]
	* Website: [http://diracvideo.org/ http://diracvideo.org]
	* Samples: [http://samples.libav.org/V-codecs/Dirac/ Libav Samples] [http://diracvideo.org/download/test-streams/raw/ DiracVideo Samples]

	== About Wavelets ==		== About Wavelets ==