Channel coupling - Revision history

Artoria2e5: Redirected page to Joint stereo

2023-07-16T05:22:20Z

Redirected page to Joint stereo

← Older revision		Revision as of 05:22, 16 July 2023
Line 1:		Line 1:
	~~'''Channel coupling''' is a method used to reduce~~ [[~~bitrate]] demand by coding the~~ stereo ~~channel information more efficiently. there are several channel coupling methods. In [[MP3]] the general term is [[joint stereo]].~~		#REDIRECT [[Joint stereo]]

	~~== MP3 Channel Coupling ==~~
	MP3 can use 2 different channel coupling methods: mid/side-coding and [[intensity stereo]]. Mid/Side-coding calculates a "mid"-channel by addition of left and right channel (l+r)/2 and a "side"-channel (l-r)/2. With more mono-like signals one can use less [[bitrate]] to encode the side-channel, so that the overall bitrate will be less than encoding the left and right channel. Intensity stereo destroys phase information, so it's used only at low bitrates.

	Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.

	~~== Vorbis Channel Coupling ==~~
	(Ogg) [[Vorbis]] treats stereo information with '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). In Vorbis, the spectrum of each channel is normalized against a floor function, which is a rough envelope of the actual spectrum. In the square polar mapping, the (stereo) phase is roughly defined as the difference between the normalized left and right amplitude of a given frequency component. If the original left and right channel are the same within a certain frequency band, apart from an overall scaling factor, then the normalized frequency spectrum is the same left and right and the stereo phase is zero over the whole frequency band. Note that in the context of polar mapping, the term 'phase' (here: 'stereo phase') has a very different meaning from the phase of a periodic wave. Unlike in the Fourier Transform, the Cosine Transform used in Vorbis and other encoders only provides amplitudes and no phases of the latter type.

	~~Once the stereo information is represented in polar mapping as a magnitude and stereo phase, Vorbis can use three coupling methods:~~
	* '''Lossless coupling''' is equivalent to independent encoding of the two channels ('dual mono' in MP3), but with the benefit of additional space-saving. It does polar mapping/channel interleaving using the residue vectors.
	* In [[point stereo]], the stereo phase is discarded completely. All the stereo information comes from the difference in the spectral floors for the left and right channels.
	* In '''phase stereo'''', the stereo phase is quantized, i.e. stored at a lower resolution. Especially above 4 kHz, the ear is not very sensitive to phase information. Phase stereo is '''not''' currently implemented in reference encoder due to complexity, but will be re-added again later on. Note that phase stereo should not be compared to intensity stereo in MP3 coding.

	Ogg Vorbis uses lossless/point stereo coupling below ''-q 6''. Lossless channel coupling is used for high bitrates entirely (''-q 6 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicity's sake.

	~~=== Additional Reading ===~~
	* [http://www.xiph.org/vorbis/doc/stereo.html Ogg Vorbis stereo-specific channel coupling] at xiph.org.

	~~[[Category:Technical~~]]

79.133.131.255: /* Vorbis Channel Coupling */ dual stereo - will be quadro :)

2013-05-10T19:59:28Z

Vorbis Channel Coupling: dual stereo - will be quadro :)

← Older revision		Revision as of 19:59, 10 May 2013
Line 10:		Line 10:

	Once the stereo information is represented in polar mapping as a magnitude and stereo phase, Vorbis can use three coupling methods:		Once the stereo information is represented in polar mapping as a magnitude and stereo phase, Vorbis can use three coupling methods:
	* '''Lossless coupling''' is equivalent to independent encoding of the two channels ('dual ~~stereo~~' in MP3), but with the benefit of additional space-saving. It does polar mapping/channel interleaving using the residue vectors.		* '''Lossless coupling''' is equivalent to independent encoding of the two channels ('dual mono' in MP3), but with the benefit of additional space-saving. It does polar mapping/channel interleaving using the residue vectors.
	* In [[point stereo]], the stereo phase is discarded completely. All the stereo information comes from the difference in the spectral floors for the left and right channels.		* In [[point stereo]], the stereo phase is discarded completely. All the stereo information comes from the difference in the spectral floors for the left and right channels.
	* In '''phase stereo'''', the stereo phase is quantized, i.e. stored at a lower resolution. Especially above 4 kHz, the ear is not very sensitive to phase information. Phase stereo is '''not''' currently implemented in reference encoder due to complexity, but will be re-added again later on. Note that phase stereo should not be compared to intensity stereo in MP3 coding.		* In '''phase stereo'''', the stereo phase is quantized, i.e. stored at a lower resolution. Especially above 4 kHz, the ear is not very sensitive to phase information. Phase stereo is '''not''' currently implemented in reference encoder due to complexity, but will be re-added again later on. Note that phase stereo should not be compared to intensity stereo in MP3 coding.

Speckmade at 16:49, 14 June 2007

2007-06-14T16:49:19Z

← Older revision		Revision as of 16:49, 14 June 2007
Line 1:		Line 1:
	'''Channel coupling''' is a method used to reduce [[bitrate]] demand by coding the stereo channel information more efficiently. there are several channel coupling methods. In [[MP3]] the general term is [[joint stereo]].		'''Channel coupling''' is a method used to reduce [[bitrate]] demand by coding the stereo channel information more efficiently. there are several channel coupling methods. In [[MP3]] the general term is [[joint stereo]].

	==MP3 Channel Coupling==		== MP3 Channel Coupling ==

	MP3 can use 2 different channel coupling methods: mid/side-coding and [[intensity stereo]]. Mid/Side-coding calculates a "mid"-channel by addition of left and right channel (l+r)/2 and a "side"-channel (l-r)/2. With more mono-like signals one can use less [[bitrate]] to encode the side-channel, so that the overall bitrate will be less than encoding the left and right channel. Intensity stereo destroys phase information, so it's used only at low bitrates.		MP3 can use 2 different channel coupling methods: mid/side-coding and [[intensity stereo]]. Mid/Side-coding calculates a "mid"-channel by addition of left and right channel (l+r)/2 and a "side"-channel (l-r)/2. With more mono-like signals one can use less [[bitrate]] to encode the side-channel, so that the overall bitrate will be less than encoding the left and right channel. Intensity stereo destroys phase information, so it's used only at low bitrates.

	Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.		Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.

			== Vorbis Channel Coupling ==
	==~~Ogg~~ Vorbis Channel Coupling==		(Ogg) [[Vorbis]] treats stereo information with '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). In Vorbis, the spectrum of each channel is normalized against a floor function, which is a rough envelope of the actual spectrum. In the square polar mapping, the (stereo) phase is roughly defined as the difference between the normalized left and right amplitude of a given frequency component. If the original left and right channel are the same within a certain frequency band, apart from an overall scaling factor, then the normalized frequency spectrum is the same left and right and the stereo phase is zero over the whole frequency band. Note that in the context of polar mapping, the term 'phase' (here: 'stereo phase') has a very different meaning from the phase of a periodic wave. Unlike in the Fourier Transform, the Cosine Transform used in Vorbis and other encoders only provides amplitudes and no phases of the latter type.

	[[~~Ogg~~ Vorbis]] treats stereo information with '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). In Vorbis, the spectrum of each channel is normalized against a floor function, which is a rough envelope of the actual spectrum. In the square polar mapping, the (stereo) phase is roughly defined as the difference between the normalized left and right amplitude of a given frequency component. If the original left and right channel are the same within a certain frequency band, apart from an overall scaling factor, then the normalized frequency spectrum is the same left and right and the stereo phase is zero over the whole frequency band. Note that in the context of polar mapping, the term 'phase' (here: 'stereo phase') has a very different meaning from the phase of a periodic wave. Unlike in the Fourier Transform, the Cosine Transform used in Vorbis and other encoders only provides amplitudes and no phases of the latter type.

	Once the stereo information is represented in polar mapping as a magnitude and stereo phase, Vorbis can use three coupling methods:		Once the stereo information is represented in polar mapping as a magnitude and stereo phase, Vorbis can use three coupling methods:

	* '''Lossless coupling''' is equivalent to independent encoding of the two channels ('dual stereo' in MP3), but with the benefit of additional space-saving. It does polar mapping/channel interleaving using the residue vectors.		* '''Lossless coupling''' is equivalent to independent encoding of the two channels ('dual stereo' in MP3), but with the benefit of additional space-saving. It does polar mapping/channel interleaving using the residue vectors.

	* In [[point stereo]], the stereo phase is discarded completely. All the stereo information comes from the difference in the spectral floors for the left and right channels.		* In [[point stereo]], the stereo phase is discarded completely. All the stereo information comes from the difference in the spectral floors for the left and right channels.

	* In '''phase stereo'''', the stereo phase is quantized, i.e. stored at a lower resolution. Especially above 4 kHz, the ear is not very sensitive to phase information. Phase stereo is '''not''' currently implemented in reference encoder due to complexity, but will be re-added again later on. Note that phase stereo should not be compared to intensity stereo in MP3 coding.		* In '''phase stereo'''', the stereo phase is quantized, i.e. stored at a lower resolution. Especially above 4 kHz, the ear is not very sensitive to phase information. Phase stereo is '''not''' currently implemented in reference encoder due to complexity, but will be re-added again later on. Note that phase stereo should not be compared to intensity stereo in MP3 coding.

	Ogg Vorbis uses lossless/point stereo coupling below ''-q 6''. Lossless channel coupling is used for high bitrates entirely (''-q 6 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicity's sake.		Ogg Vorbis uses lossless/point stereo coupling below ''-q 6''. Lossless channel coupling is used for high bitrates entirely (''-q 6 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicity's sake.

	===Additional Reading===		=== Additional Reading ===
	* [http://www.xiph.org/vorbis/doc/stereo.html Ogg Vorbis stereo-specific channel coupling] at xiph.org.		* [http://www.xiph.org/vorbis/doc/stereo.html Ogg Vorbis stereo-specific channel coupling] at xiph.org.

	[[Category:Technical]]		[[Category:Technical]]

Pepoluan: Category:Technical

2006-09-11T22:38:57Z

Category:Technical

← Older revision		Revision as of 22:38, 11 September 2006
Line 1:		Line 1:
	Channel coupling is a method used to reduce [[bitrate]] demand by coding the stereo channel information more efficiently. there are several channel coupling methods. In ~~mp3~~ the general term is [[joint stereo]].		'''Channel coupling''' is a method used to reduce [[bitrate]] demand by coding the stereo channel information more efficiently. there are several channel coupling methods. In [[MP3]] the general term is [[joint stereo]].

	[[MP3]] can use 2 different channel coupling methods: mid/side-coding and [[intensity stereo]]. Mid/Side-coding calculates a "mid"-channel by addition of left and right channel (l+r)/2 and a "side"-channel (l-r)/2. With more mono-like signals one can use less [[bitrate]] to encode the side-channel, so that the overall bitrate will be less than encoding the left and right channel. Intensity stereo destroys phase information, so it's used only at low bitrates.		==MP3 Channel Coupling==

			MP3 can use 2 different channel coupling methods: mid/side-coding and [[intensity stereo]]. Mid/Side-coding calculates a "mid"-channel by addition of left and right channel (l+r)/2 and a "side"-channel (l-r)/2. With more mono-like signals one can use less [[bitrate]] to encode the side-channel, so that the overall bitrate will be less than encoding the left and right channel. Intensity stereo destroys phase information, so it's used only at low bitrates.

	Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.		Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.


			==Ogg Vorbis Channel Coupling==

	[[Ogg Vorbis]] treats stereo information with '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). In Vorbis, the spectrum of each channel is normalized against a floor function, which is a rough envelope of the actual spectrum. In the square polar mapping, the (stereo) phase is roughly defined as the difference between the normalized left and right amplitude of a given frequency component. If the original left and right channel are the same within a certain frequency band, apart from an overall scaling factor, then the normalized frequency spectrum is the same left and right and the stereo phase is zero over the whole frequency band. Note that in the context of polar mapping, the term 'phase' (here: 'stereo phase') has a very different meaning from the phase of a periodic wave. Unlike in the Fourier Transform, the Cosine Transform used in Vorbis and other encoders only provides amplitudes and no phases of the latter type.		[[Ogg Vorbis]] treats stereo information with '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). In Vorbis, the spectrum of each channel is normalized against a floor function, which is a rough envelope of the actual spectrum. In the square polar mapping, the (stereo) phase is roughly defined as the difference between the normalized left and right amplitude of a given frequency component. If the original left and right channel are the same within a certain frequency band, apart from an overall scaling factor, then the normalized frequency spectrum is the same left and right and the stereo phase is zero over the whole frequency band. Note that in the context of polar mapping, the term 'phase' (here: 'stereo phase') has a very different meaning from the phase of a periodic wave. Unlike in the Fourier Transform, the Cosine Transform used in Vorbis and other encoders only provides amplitudes and no phases of the latter type.
Line 17:		Line 22:
	Ogg Vorbis uses lossless/point stereo coupling below ''-q 6''. Lossless channel coupling is used for high bitrates entirely (''-q 6 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicity's sake.		Ogg Vorbis uses lossless/point stereo coupling below ''-q 6''. Lossless channel coupling is used for high bitrates entirely (''-q 6 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicity's sake.

	~~See also~~ [http://www.xiph.org/vorbis/doc/stereo.html Ogg Vorbis stereo-specific channel coupling] at xiph.org.		===Additional Reading===
			* [http://www.xiph.org/vorbis/doc/stereo.html Ogg Vorbis stereo-specific channel coupling] at xiph.org.

			[[Category:Technical]]

HotshotGG at 01:25, 28 May 2006

2006-05-28T01:25:33Z

← Older revision		Revision as of 01:25, 28 May 2006
Line 5:		Line 5:
	Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.		Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.

	[[Ogg Vorbis]] treats stereo information with '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). In Vorbis, the spectrum of each channel is normalized against a floor function, which is a rough envelope of the actual spectrum. In the square polar mapping, the (stereo) phase is roughly defined as the difference between the normalized left and right amplitude of a given frequency component. If the original left and right channel are the same within a certain frequency band, apart from an overall scaling factor, then the normalized frequency spectrum is the same left and right and the stereo phase is zero over the whole frequency band. Note that in the context of polar mapping, the term 'phase' (here: 'stereo phase') has a very different meaning from the phase of a periodic wave. Unlike in the Fourier ~~transform~~, the ~~cosine transform~~ used in Vorbis and other encoders only provides amplitudes and no phases of the latter type.		[[Ogg Vorbis]] treats stereo information with '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). In Vorbis, the spectrum of each channel is normalized against a floor function, which is a rough envelope of the actual spectrum. In the square polar mapping, the (stereo) phase is roughly defined as the difference between the normalized left and right amplitude of a given frequency component. If the original left and right channel are the same within a certain frequency band, apart from an overall scaling factor, then the normalized frequency spectrum is the same left and right and the stereo phase is zero over the whole frequency band. Note that in the context of polar mapping, the term 'phase' (here: 'stereo phase') has a very different meaning from the phase of a periodic wave. Unlike in the Fourier Transform, the Cosine Transform used in Vorbis and other encoders only provides amplitudes and no phases of the latter type.

	Once the stereo information is represented in polar mapping as a magnitude and stereo phase, Vorbis can use three coupling methods:		Once the stereo information is represented in polar mapping as a magnitude and stereo phase, Vorbis can use three coupling methods:

Hankwang: Major rewrite of the Vorbis part.

2006-03-26T19:39:49Z

Major rewrite of the Vorbis part.

← Older revision		Revision as of 19:39, 26 March 2006
Line 5:		Line 5:
	Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.		Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.

	[[Ogg Vorbis]] ~~can use a mixture between 3 different types of channel coupling methods: phase~~ stereo~~, [[point stereo]], and lossless. These are all based upon~~ '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). ~~Phase stereo~~ is the ~~"least agressive means" of quantization~~. ~~It effects only "diffuse imaging" or ''~~(~~angle~~)~~'' information, due to~~ the ~~fact that~~ the ~~ear is least sensitive to [http://en.wikipedia.org/wiki/In_phase in-phase] or [http://en.wikipedia.org/wiki/Out_of_phase out-~~of~~-phase] noise above 4 kHz~~. ~~Phase stereo~~ is ~~'''not''' curerently implemented in reference encoder due to complexity, but will be re-added again later on. [[Point~~ stereo]] is ~~a "more agressive means" of quantization~~. ~~It eleminates~~ the ~~possibility~~ of ~~an out-of-~~phase ~~signal~~ ''~~entirely'' as to only have an effect of "point imaging" or~~ '~~'(magnitude~~)~~'' information, hence~~ the ~~amplitude~~. ~~It is currently used~~ in the ~~reference encoder on all modes below a -q 6. Lossless coupling just does polar mapping/channel interleaving using~~ the ~~residue vectors~~ and ~~has a bit-for-bit identical output~~. ~~''Note: also that phase stereo should not be compared to intensity stereo in MP3 coding''~~		[[Ogg Vorbis]] treats stereo information with '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). In Vorbis, the spectrum of each channel is normalized against a floor function, which is a rough envelope of the actual spectrum. In the square polar mapping, the (stereo) phase is roughly defined as the difference between the normalized left and right amplitude of a given frequency component. If the original left and right channel are the same within a certain frequency band, apart from an overall scaling factor, then the normalized frequency spectrum is the same left and right and the stereo phase is zero over the whole frequency band. Note that in the context of polar mapping, the term 'phase' (here: 'stereo phase') has a very different meaning from the phase of a periodic wave. Unlike in the Fourier transform, the cosine transform used in Vorbis and other encoders only provides amplitudes and no phases of the latter type.

	Ogg Vorbis uses lossless/point stereo coupling below (''-q 6''). ~~lossless~~ channel coupling is used for high bitrates entirely (''-q 6 and up''). This can be adjusted via an advanced-encode switch, but is not done for ~~simplicit~~ sake.		Once the stereo information is represented in polar mapping as a magnitude and stereo phase, Vorbis can use three coupling methods:

			* '''Lossless coupling''' is equivalent to independent encoding of the two channels ('dual stereo' in MP3), but with the benefit of additional space-saving. It does polar mapping/channel interleaving using the residue vectors.

			* In [[point stereo]], the stereo phase is discarded completely. All the stereo information comes from the difference in the spectral floors for the left and right channels.

			* In '''phase stereo'''', the stereo phase is quantized, i.e. stored at a lower resolution. Especially above 4 kHz, the ear is not very sensitive to phase information. Phase stereo is '''not''' currently implemented in reference encoder due to complexity, but will be re-added again later on. Note that phase stereo should not be compared to intensity stereo in MP3 coding.

			Ogg Vorbis uses lossless/point stereo coupling below ''-q 6''. Lossless channel coupling is used for high bitrates entirely (''-q 6 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicity's sake.

			See also [http://www.xiph.org/vorbis/doc/stereo.html Ogg Vorbis stereo-specific channel coupling] at xiph.org.

Foot: tag fix

2005-08-21T01:12:19Z

tag fix

← Older revision		Revision as of 01:12, 21 August 2005
Line 1:		Line 1:
	Channel coupling is a method used to reduce [[bitrate]] demand by coding the stereo channel information more efficiently. there are several channel coupling methods. In mp3 the general term is [[joint stereo]].		Channel coupling is a method used to reduce [[bitrate]] demand by coding the stereo channel information more efficiently. there are several channel coupling methods. In mp3 the general term is [[joint stereo]].

	[[MP3]] can use 2 different channel coupling methods: mid/side-coding and [[intensity stereo]]. Mid/Side-coding calculates a "mid"-channel by addition of left and right channel (l+r)/2 and a "side"-channel (l-r)/2. With more mono-like signals one can use less bitrate]] to encode the side-channel, so that the overall bitrate will be less than encoding the left and right channel. Intensity stereo destroys phase information, so it's used only at low bitrates.		[[MP3]] can use 2 different channel coupling methods: mid/side-coding and [[intensity stereo]]. Mid/Side-coding calculates a "mid"-channel by addition of left and right channel (l+r)/2 and a "side"-channel (l-r)/2. With more mono-like signals one can use less [[bitrate]] to encode the side-channel, so that the overall bitrate will be less than encoding the left and right channel. Intensity stereo destroys phase information, so it's used only at low bitrates.

	Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.		Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.

HotshotGG at 02:04, 8 August 2005

2005-08-08T02:04:29Z

← Older revision		Revision as of 02:04, 8 August 2005
Line 5:		Line 5:
	Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.		Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.

	[[Ogg Vorbis]] can use a mixture between 3 different types of channel coupling methods: phase stereo, [[point stereo]], and lossless. These are all based upon '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). Phase stereo is the "least agressive means" of quantization. It effects only "diffuse imaging" or ''(angle)'' information, due to the fact that the ear is least sensitive to [http://en.wikipedia.org/wiki/In_phase in-phase] or [http://en.wikipedia.org/wiki/Out_of_phase out-of-phase] noise above 4 kHz. Phase stereo is '''not''' curerently implemented in reference encoder due to complexity, but will be re-added again later on. [[Point stereo]] is a "more agressive means" of quantization. It eleminates the possibility of an out-of-phase signal ''entirely'' as to only have an effect of "point imaging" or ''(magnitude)'' information, hence the amplitude. It is currently used in the reference encoder on all modes below a -q 5. Lossless coupling just does polar mapping/channel interleaving using the residue vectors and has a bit-for-bit identical output. ''Note: also that phase stereo should not be compared to intensity stereo in MP3 coding''		[[Ogg Vorbis]] can use a mixture between 3 different types of channel coupling methods: phase stereo, [[point stereo]], and lossless. These are all based upon '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). Phase stereo is the "least agressive means" of quantization. It effects only "diffuse imaging" or ''(angle)'' information, due to the fact that the ear is least sensitive to [http://en.wikipedia.org/wiki/In_phase in-phase] or [http://en.wikipedia.org/wiki/Out_of_phase out-of-phase] noise above 4 kHz. Phase stereo is '''not''' curerently implemented in reference encoder due to complexity, but will be re-added again later on. [[Point stereo]] is a "more agressive means" of quantization. It eleminates the possibility of an out-of-phase signal ''entirely'' as to only have an effect of "point imaging" or ''(magnitude)'' information, hence the amplitude. It is currently used in the reference encoder on all modes below a -q 6. Lossless coupling just does polar mapping/channel interleaving using the residue vectors and has a bit-for-bit identical output. ''Note: also that phase stereo should not be compared to intensity stereo in MP3 coding''

	Ogg Vorbis uses lossless/point stereo coupling below (''-q 6''). lossless channel coupling is used for high bitrates entirely (''-q 6 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicit sake.		Ogg Vorbis uses lossless/point stereo coupling below (''-q 6''). lossless channel coupling is used for high bitrates entirely (''-q 6 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicit sake.

HotshotGG at 02:03, 8 August 2005

2005-08-08T02:03:33Z

← Older revision		Revision as of 02:03, 8 August 2005
Line 7:		Line 7:
	[[Ogg Vorbis]] can use a mixture between 3 different types of channel coupling methods: phase stereo, [[point stereo]], and lossless. These are all based upon '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). Phase stereo is the "least agressive means" of quantization. It effects only "diffuse imaging" or ''(angle)'' information, due to the fact that the ear is least sensitive to [http://en.wikipedia.org/wiki/In_phase in-phase] or [http://en.wikipedia.org/wiki/Out_of_phase out-of-phase] noise above 4 kHz. Phase stereo is '''not''' curerently implemented in reference encoder due to complexity, but will be re-added again later on. [[Point stereo]] is a "more agressive means" of quantization. It eleminates the possibility of an out-of-phase signal ''entirely'' as to only have an effect of "point imaging" or ''(magnitude)'' information, hence the amplitude. It is currently used in the reference encoder on all modes below a -q 5. Lossless coupling just does polar mapping/channel interleaving using the residue vectors and has a bit-for-bit identical output. ''Note: also that phase stereo should not be compared to intensity stereo in MP3 coding''		[[Ogg Vorbis]] can use a mixture between 3 different types of channel coupling methods: phase stereo, [[point stereo]], and lossless. These are all based upon '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). Phase stereo is the "least agressive means" of quantization. It effects only "diffuse imaging" or ''(angle)'' information, due to the fact that the ear is least sensitive to [http://en.wikipedia.org/wiki/In_phase in-phase] or [http://en.wikipedia.org/wiki/Out_of_phase out-of-phase] noise above 4 kHz. Phase stereo is '''not''' curerently implemented in reference encoder due to complexity, but will be re-added again later on. [[Point stereo]] is a "more agressive means" of quantization. It eleminates the possibility of an out-of-phase signal ''entirely'' as to only have an effect of "point imaging" or ''(magnitude)'' information, hence the amplitude. It is currently used in the reference encoder on all modes below a -q 5. Lossless coupling just does polar mapping/channel interleaving using the residue vectors and has a bit-for-bit identical output. ''Note: also that phase stereo should not be compared to intensity stereo in MP3 coding''

	Ogg Vorbis uses lossless/point stereo coupling below (''-q 5''). lossless channel coupling is used for high bitrates entirely (''-q 5 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicit sake.		Ogg Vorbis uses lossless/point stereo coupling below (''-q 6''). lossless channel coupling is used for high bitrates entirely (''-q 6 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicit sake.

HotshotGG at 06:21, 27 July 2005

2005-07-27T06:21:29Z

← Older revision		Revision as of 06:21, 27 July 2005
Line 5:		Line 5:
	Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.		Correctly implemented MP3 mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.

	[[Ogg Vorbis]] can use a mixture between 3 different types of channel coupling methods: phase stereo, [[point stereo]], and lossless. These are all based upon '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). Phase stereo is the "least agressive means" of quantization. It effects only "diffuse imaging" or ''(angle)'' information, due to the fact that the ear is least sensitive to [http://en.wikipedia.org/wiki/In_phase in-phase] or [http://en.wikipedia.org/wiki/Out_of_phase out-of-phase] noise above 4 kHz. Phase stereo is '''not''' curerently implemented in reference encoder due to complexity, but will be re-added again later on. [[Point stereo]] is a "more agressive means" of quantization. It eleminates the possibility of an out-of-phase signal ''entirely'' as to only have an effect of "point imaging" or ''(magnitude)'' information, hence the amplitude. It is currently used in the reference encoder on all modes below a -q 5. Lossless coupling just does polar mapping/channel interleaving using the residue vectors and has a bit-for-bit identical output. Note: also that phase stereo should not be compared to intensity stereo in MP3 coding.		[[Ogg Vorbis]] can use a mixture between 3 different types of channel coupling methods: phase stereo, [[point stereo]], and lossless. These are all based upon '''square polar mapping''' which is beneficial when the correlation between the left and right channels are strong (this can also be extended to multichannel coupling as well). Phase stereo is the "least agressive means" of quantization. It effects only "diffuse imaging" or ''(angle)'' information, due to the fact that the ear is least sensitive to [http://en.wikipedia.org/wiki/In_phase in-phase] or [http://en.wikipedia.org/wiki/Out_of_phase out-of-phase] noise above 4 kHz. Phase stereo is '''not''' curerently implemented in reference encoder due to complexity, but will be re-added again later on. [[Point stereo]] is a "more agressive means" of quantization. It eleminates the possibility of an out-of-phase signal ''entirely'' as to only have an effect of "point imaging" or ''(magnitude)'' information, hence the amplitude. It is currently used in the reference encoder on all modes below a -q 5. Lossless coupling just does polar mapping/channel interleaving using the residue vectors and has a bit-for-bit identical output. ''Note: also that phase stereo should not be compared to intensity stereo in MP3 coding''

	Ogg Vorbis uses lossless/point stereo coupling below (''-q 5''). lossless channel coupling is used for high bitrates entirely (''-q 5 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicit sake.		Ogg Vorbis uses lossless/point stereo coupling below (''-q 5''). lossless channel coupling is used for high bitrates entirely (''-q 5 and up''). This can be adjusted via an advanced-encode switch, but is not done for simplicit sake.