Ghost - Revision history

Gmaxwell: Reverted edits by Domtheo (talk) to last revision by DOS386

2013-11-13T07:00:39Z

Reverted edits by Domtheo (talk) to last revision by DOS386

← Older revision		Revision as of 07:00, 13 November 2013
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	Just a fancy name for sub-bands with non-uniform width. Probably similar to having an MDCT with few sub-bands, except that that the sub-bands could follow (roughly) the critical bands.		Just a fancy name for sub-bands with non-uniform width. Probably similar to having an MDCT with few sub-bands, except that that the sub-bands could follow (roughly) the critical bands.
	~~[http://vamostech.com/gps-tracking Gps tracker motor], [http://vamostech.com/gps-tracking Gps tracking mobil]~~

	=== LPC + stochastic cb ===		=== LPC + stochastic cb ===

	Like CELP with no pitch. Could be used to code the noisy part of the signal with low bit-rate. Would need to figure out how to preserve the energy of the noise when going with 1/2 bit per sample and less.		Like CELP with no pitch. Could be used to code the noisy part of the signal with low bit-rate. Would need to figure out how to preserve the energy of the noise when going with 1/2 bit per sample and less.
	~~[http://kiosauto.com Aksesoris mobil], [http://www.awanirentcar.com Sewa mobil jakarta pusat]~~

	== Codec Structure Ideas ==		== Codec Structure Ideas ==

Domtheo at 06:59, 13 November 2013

2013-11-13T06:59:40Z

← Older revision		Revision as of 06:59, 13 November 2013
Line 32:		Line 32:

	Just a fancy name for sub-bands with non-uniform width. Probably similar to having an MDCT with few sub-bands, except that that the sub-bands could follow (roughly) the critical bands.		Just a fancy name for sub-bands with non-uniform width. Probably similar to having an MDCT with few sub-bands, except that that the sub-bands could follow (roughly) the critical bands.
			[http://vamostech.com/gps-tracking Gps tracker motor], [http://vamostech.com/gps-tracking Gps tracking mobil]

	=== LPC + stochastic cb ===		=== LPC + stochastic cb ===

	Like CELP with no pitch. Could be used to code the noisy part of the signal with low bit-rate. Would need to figure out how to preserve the energy of the noise when going with 1/2 bit per sample and less.		Like CELP with no pitch. Could be used to code the noisy part of the signal with low bit-rate. Would need to figure out how to preserve the energy of the noise when going with 1/2 bit per sample and less.
			[http://kiosauto.com Aksesoris mobil], [http://www.awanirentcar.com Sewa mobil jakarta pusat]

	== Codec Structure Ideas ==		== Codec Structure Ideas ==

DOS386: obsolete too???

2012-12-22T16:17:48Z

obsolete too???

← Older revision		Revision as of 16:17, 22 December 2012
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			{{historical}}
	This page is meant to track ideas about low-delay, high-quality audio coding. The work has just started, so don't expect anything in the near future (or at all for that matter).		This page is meant to track ideas about low-delay, high-quality audio coding. The work has just started, so don't expect anything in the near future (or at all for that matter).

Ogg.k.ogg.k: I must with the greatest regret consign this valuable information to the bin of history.

2011-09-23T10:58:22Z

I must with the greatest regret consign this valuable information to the bin of history.

Show changes

EHelman29: None

2011-09-23T10:19:16Z

None

Show changes

Ssp: /* Signal types */

2011-01-13T15:49:50Z

Signal types

← Older revision		Revision as of 15:49, 13 January 2011
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	** Many (sometimes closely spaced) harmonics		** Many (sometimes closely spaced) harmonics
	* Shapred noise		* Shapred noise
	** Signals that are (or are indistinguishable) ~~from~~ filtered (coloured) white noise		** Signals that are (or are indistinguishable from) filtered (coloured) white noise
	* Transients		* Transients
	** Whatever doesn’t fit above I guess		** Whatever doesn’t fit above I guess

Bugmenot: /* Signal types */ typo

2007-09-20T04:51:32Z

Signal types: typo

← Older revision		Revision as of 04:51, 20 September 2007
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	** Signals that are (or are indistinguishable) from filtered (coloured) white noise		** Signals that are (or are indistinguishable) from filtered (coloured) white noise
	* Transients		* Transients
	** Whatever ~~does't~~ fit above I guess		** Whatever doesn’t fit above I guess

	== Signal analysis ==		== Signal analysis ==

Jmspeex: comments on quantization

2006-06-28T12:45:58Z

comments on quantization

← Older revision		Revision as of 12:45, 28 June 2006
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	After the sinusoids have been extracted they have to be quantized. The possible ways are		After the sinusoids have been extracted they have to be quantized. The possible ways are
	* Sort the sinusoids according to energy and transmit only a finite number or only ones with a specific energy or above. The indices of the sinusoids before rearranging will have to be sent.		* Sort the sinusoids according to energy and transmit only a finite number or only ones with a specific energy or above. The indices of the sinusoids before rearranging will have to be sent.
			** I think it's worth checking which is most efficient. Sorting the sinusoids will help quantizing the amplitude, but make it harder to encode frequency. [[User:Jmspeex\|Jmspeex]] 05:45, 28 June 2006 (PDT)
	* Use the psycho acoustic properties and remove all the sinusoids, which will be masked by other tones.		* Use the psycho acoustic properties and remove all the sinusoids, which will be masked by other tones.
			** Of course, we don't want to encode perceptually irrelevant sinusoids. Actually, we want the resolution (in amplitude, phase and probably frequency) to scale with the amplitude-to-mask ratio or something like that. [[User:Jmspeex\|Jmspeex]] 05:45, 28 June 2006 (PDT)
	* After removing perceptually irrelevant and low-energy tones the energy in each critical bands has to be adjusted to match with the initial energy.		* After removing perceptually irrelevant and low-energy tones the energy in each critical bands has to be adjusted to match with the initial energy.
			** Possibly -- I don't know much on that topic. Monty probably has valuable experience. [[User:Jmspeex\|Jmspeex]] 05:45, 28 June 2006 (PDT)
	* Time-differential coding of sinusoids across frames can be used		* Time-differential coding of sinusoids across frames can be used
			** Definitely. This is very important if we plan on using short frames. It would be important to minimize inter-frame redundancy, but still make it possible to recover from packet loss. For that, we could either use a leaky predictor (like the pitch in CELP) or use key-frames (like a video codec). [[User:Jmspeex\|Jmspeex]] 05:45, 28 June 2006 (PDT)

	==== Quantization of frequencies====		==== Quantization of frequencies====
	* Quantize frequencies of a few selected sinusoids and recreate other values using interpolation.		* Quantize frequencies of a few selected sinusoids and recreate other values using interpolation.
			** How would you do that? (maybe I'm not following here) [[User:Jmspeex\|Jmspeex]] 05:45, 28 June 2006 (PDT)
	==== Quantization of Amplitudes ====		==== Quantization of Amplitudes ====
	* Model the energy curve of the sinusoids – for instance using an exponential curve		* Model the energy curve of the sinusoids – for instance using an exponential curve
			** Exponential decay might be a good way to do inter-frame prediction. [[User:Jmspeex\|Jmspeex]] 05:45, 28 June 2006 (PDT)
	* Quantize amplitudes of a few selected sinusoids and recreate other values using interpolation.		* Quantize amplitudes of a few selected sinusoids and recreate other values using interpolation.
			** Possibly, but probably not at first (hard problem). [[User:Jmspeex\|Jmspeex]] 05:45, 28 June 2006 (PDT)
	==== Quantization of phase and modulation parameters ====		==== Quantization of phase and modulation parameters ====
	* Can be scalar quantized with the number of bits allocated being proportional to the energy of the sinusoid		* Can be scalar quantized with the number of bits allocated being proportional to the energy of the sinusoid
			** Yes. Also, this is something that can be predicted very well across frames. It's not even necessary to make that one robust to losses, because as long as the phase is continuous, no one will notice [[User:Jmspeex\|Jmspeex]] 05:45, 28 June 2006 (PDT)
	==== Quantization of indices ====		==== Quantization of indices ====
	==== Quantization of energy gains in critical bands ====		==== Quantization of energy gains in critical bands ====
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	=== Excitation similarity weighting ===		=== Excitation similarity weighting ===
	The idea behind the ESW technique is to select sinusoids such that each new sinusoid added will provide a maximum incremental gain in matching between the auditory excitation pattern associated with the original signal and the auditory excitation pattern associated with the modeled signal. In order to accomplish this goal, an iterative process is proposed in which each sinusoid extracted during conventional analysis is assigned an excitation similarity weight. During each iteration, the sinusoid having the largest weight is added to the modeled representation. New sinusoids are accumulated until some constrain is exhausted, for example, a bit budget. The algorithm tends to converge as the number of modeled sinusoids increases		The idea behind the ESW technique is to select sinusoids such that each new sinusoid added will provide a maximum incremental gain in matching between the auditory excitation pattern associated with the original signal and the auditory excitation pattern associated with the modeled signal. In order to accomplish this goal, an iterative process is proposed in which each sinusoid extracted during conventional analysis is assigned an excitation similarity weight. During each iteration, the sinusoid having the largest weight is added to the modeled representation. New sinusoids are accumulated until some constrain is exhausted, for example, a bit budget. The algorithm tends to converge as the number of modeled sinusoids increases

			-- Not sure I understand here. Any reference? [[User:Jmspeex\|Jmspeex]] 05:45, 28 June 2006 (PDT)

	=== Trajectory tracking ===		=== Trajectory tracking ===
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	*Amplitudes are linearly interpolated		*Amplitudes are linearly interpolated
	* Phase interpolated with cubic polynomials		* Phase interpolated with cubic polynomials

			-- Any reference? [[User:Jmspeex\|Jmspeex]] 05:45, 28 June 2006 (PDT)

Anup at 11:21, 28 June 2006

2006-06-28T11:21:25Z

← Older revision		Revision as of 11:21, 28 June 2006
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	* Time-differential coding of sinusoids across frames can be used		* Time-differential coding of sinusoids across frames can be used

	=== Quantization of frequencies		==== Quantization of frequencies====
	* Quantize frequencies of a few selected sinusoids and recreate other values using interpolation.		* Quantize frequencies of a few selected sinusoids and recreate other values using interpolation.
	=== Quantization of Amplitudes ===		==== Quantization of Amplitudes ====
	* Model the energy curve of the sinusoids – for instance using an exponential curve		* Model the energy curve of the sinusoids – for instance using an exponential curve
	* Quantize amplitudes of a few selected sinusoids and recreate other values using interpolation.		* Quantize amplitudes of a few selected sinusoids and recreate other values using interpolation.
	=== Quantization of phase and modulation parameters ===		==== Quantization of phase and modulation parameters ====
	* Can be scalar quantized with the number of bits allocated being proportional to the energy of the sinusoid		* Can be scalar quantized with the number of bits allocated being proportional to the energy of the sinusoid
	=== Quantization of indices ===		==== Quantization of indices ====
	=== Quantization of energy gains in critical bands ===		==== Quantization of energy gains in critical bands ====

	=== Excitation similarity weighting ===		=== Excitation similarity weighting ===

Anup at 11:19, 28 June 2006

2006-06-28T11:19:56Z

← Older revision		Revision as of 11:19, 28 June 2006
Line 77:		Line 77:

	==== Phase lock loop (PLL) ====		==== Phase lock loop (PLL) ====

			== Quantization Ideas ==
			After the sinusoids have been extracted they have to be quantized. The possible ways are
			* Sort the sinusoids according to energy and transmit only a finite number or only ones with a specific energy or above. The indices of the sinusoids before rearranging will have to be sent.
			* Use the psycho acoustic properties and remove all the sinusoids, which will be masked by other tones.
			* After removing perceptually irrelevant and low-energy tones the energy in each critical bands has to be adjusted to match with the initial energy.
			* Time-differential coding of sinusoids across frames can be used

			=== Quantization of frequencies
			* Quantize frequencies of a few selected sinusoids and recreate other values using interpolation.
			=== Quantization of Amplitudes ===
			* Model the energy curve of the sinusoids – for instance using an exponential curve
			* Quantize amplitudes of a few selected sinusoids and recreate other values using interpolation.
			=== Quantization of phase and modulation parameters ===
			* Can be scalar quantized with the number of bits allocated being proportional to the energy of the sinusoid
			=== Quantization of indices ===
			=== Quantization of energy gains in critical bands ===

			=== Excitation similarity weighting ===
			The idea behind the ESW technique is to select sinusoids such that each new sinusoid added will provide a maximum incremental gain in matching between the auditory excitation pattern associated with the original signal and the auditory excitation pattern associated with the modeled signal. In order to accomplish this goal, an iterative process is proposed in which each sinusoid extracted during conventional analysis is assigned an excitation similarity weight. During each iteration, the sinusoid having the largest weight is added to the modeled representation. New sinusoids are accumulated until some constrain is exhausted, for example, a bit budget. The algorithm tends to converge as the number of modeled sinusoids increases

			=== Trajectory tracking ===
			Once the meaningful sinusoidal peaks and their parameters have been estimated, the peaks are tracked together into inter-frame trajectories. At each frame, a peak continuation algorithm tries to connect the sinusoidal peak into the already existing trajectories at the previous frame, resulting into a smooth curve of frequencies and amplitudes. The continuation was tested with two algorithms: the traditional one which uses only the parameters of the sinusoids to obtain smooth trajectories and one original method which synthesizes the possible continuations inside certain deviation limits and compares them to the original signal. There is also other systems which use more advanced methods, for example the Hidden Markov Models to track the trajectories.
			Sinusoidal trajectories contain all the information needed for the reconstruction of the harmonic parts of input signals: amplitudes, frequencies and phases of each trajectory at each frame. To avoid discontinuities at frame boundaries, the amplitudes, frequencies and phases are interpolated from frame to frame.
			*Amplitudes are linearly interpolated
			* Phase interpolated with cubic polynomials