CEFT - Revision history

EPirat: Redirect to the correct site

2016-06-23T12:20:29Z

Redirect to the correct site

← Older revision	Revision as of 12:20, 23 June 2016
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		#REDIRECT [[Constrained-Energy_Fourier_Transforms]]

MrZeus: move CEFT page to expanded page name, since it's an orphan at the mo anyway

2015-08-26T10:28:04Z

move CEFT page to expanded page name, since it's an orphan at the mo anyway

← Older revision		Revision as of 10:28, 26 August 2015
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	~~== Constrained-Energy Fourier Transforms ==~~

	~~=== Problems with current implementation and possible solutions ===~~

	~~==== Overlapped FFT not critically sampled ====~~

	~~In the current implementation, we encode 4/3 times more samples than necessary because we use 256-point FFTs with 64 samples overlap.~~

	~~Ideas:~~
	* Use an MDCT instead of the FFT
	* Do extrapolation on the input and use a wider FFT. Then optimise the search only for the "real" samples

	~~==== Non-harmonic signals (i.e. music) ====~~

	~~CEFT only works on speech because most of its coding efficiency is provided by the pitch predictor.~~

	~~Ideas:~~
	* Sinusoidal prediction
	* Use two (or more) pitch periods and choose one for each bin/band/whatever
	* Use two (or more) pitch periods at the same time and use energy conservation to keep everything stable.

	~~==== Sparse spectrum ====~~

	~~CEFT tends to have musical noise, especially at high frequency when there are very few bits/bin.~~

	~~Ideas:~~
	* Use a "rotation matrix"
	* Prediction from lower frequencies

	~~[[Category:Opus]]~~

Martin.leese: Promoted everything up a level heading (Level 1 is the page title)

2015-08-23T16:03:29Z

Promoted everything up a level heading (Level 1 is the page title)

← Older revision		Revision as of 16:03, 23 August 2015
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	= Constrained-Energy Fourier ~~Tranforms~~ =		== Constrained-Energy Fourier Transforms ==

	== Problems with current implementation and possible solutions ==		=== Problems with current implementation and possible solutions ===

	=== Overlapped FFT not critically sampled ===		==== Overlapped FFT not critically sampled ====

	In the current implementation, we encode 4/3 times more samples than necessary because we use 256-point FFTs with 64 samples overlap.		In the current implementation, we encode 4/3 times more samples than necessary because we use 256-point FFTs with 64 samples overlap.
Line 11:		Line 11:
	* Do extrapolation on the input and use a wider FFT. Then optimise the search only for the "real" samples		* Do extrapolation on the input and use a wider FFT. Then optimise the search only for the "real" samples

	=== Non-harmonic signals (i.e. music) ===		==== Non-harmonic signals (i.e. music) ====

	CEFT only works on speech because most of its coding efficiency is provided by the pitch predictor.		CEFT only works on speech because most of its coding efficiency is provided by the pitch predictor.
Line 20:		Line 20:
	* Use two (or more) pitch periods at the same time and use energy conservation to keep everything stable.		* Use two (or more) pitch periods at the same time and use energy conservation to keep everything stable.

	=== Sparse spectrum ===		==== Sparse spectrum ====

	CEFT tends to have musical noise, especially at high frequency when there are very few bits/bin.		CEFT tends to have musical noise, especially at high frequency when there are very few bits/bin.

MrZeus: /* CEFT */ expand acronym once on this page...

2015-08-22T22:43:44Z

CEFT: expand acronym once on this page...

← Older revision		Revision as of 22:43, 22 August 2015
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	= ~~CEFT~~ =		= Constrained-Energy Fourier Tranforms =

	== Problems with current implementation and possible solutions ==		== Problems with current implementation and possible solutions ==

MrZeus at 23:12, 18 August 2015

2015-08-18T23:12:28Z

← Older revision		Revision as of 23:12, 18 August 2015
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	* Use a "rotation matrix"		* Use a "rotation matrix"
	* Prediction from lower frequencies		* Prediction from lower frequencies

			[[Category:Opus]]

Jmspeex at 03:17, 22 November 2007

2007-11-22T03:17:20Z

← Older revision		Revision as of 03:17, 22 November 2007
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	=== Overlapped FFT not critically sampled ===		=== Overlapped FFT not critically sampled ===

			In the current implementation, we encode 4/3 times more samples than necessary because we use 256-point FFTs with 64 samples overlap.

	Ideas:		Ideas:
Line 10:		Line 12:

	=== Non-harmonic signals (i.e. music) ===		=== Non-harmonic signals (i.e. music) ===

			CEFT only works on speech because most of its coding efficiency is provided by the pitch predictor.

	Ideas:		Ideas:
Line 17:		Line 21:

	=== Sparse spectrum ===		=== Sparse spectrum ===

			CEFT tends to have musical noise, especially at high frequency when there are very few bits/bin.

	Ideas:		Ideas:
	* Use a "rotation matrix"		* Use a "rotation matrix"
	* Prediction from lower frequencies		* Prediction from lower frequencies

Jmspeex: Some ideas about CEFT

2007-11-22T03:09:12Z

Some ideas about CEFT

New page

= CEFT =

== Problems with current implementation and possible solutions ==

=== Overlapped FFT not critically sampled ===

Ideas:
* Use an MDCT instead of the FFT
* Do extrapolation on the input and use a wider FFT. Then optimise the search only for the "real" samples

=== Non-harmonic signals (i.e. music) ===

Ideas:
* Sinusoidal prediction
* Use two (or more) pitch periods and choose one for each bin/band/whatever
* Use two (or more) pitch periods at the same time and use energy conservation to keep everything stable.

=== Sparse spectrum ===

Ideas:
* Use a "rotation matrix"
* Prediction from lower frequencies