Advanced Audio Coding - Revision history

Artoria2e5: /* Encoders / Decoders (Supported Platforms) */

2023-04-23T14:03:18Z

Encoders / Decoders (Supported Platforms)

← Older revision		Revision as of 14:03, 23 April 2023
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	* [[Apple AAC]] (MacOS X,Windows)		* [[Apple AAC]] (MacOS X,Windows)
	* [[libavcodec AAC\|FFmpeg 3.0+ native AAC encoder]] (Multiplatform)		* [[libavcodec AAC\|FFmpeg 3.0+ native AAC encoder]] (Multiplatform)
			* [https://gitlab.com/ecodis/exhale exhale] (xHE-AAC only, Multiplatform, experimental)

			=== Obsolete ===
	* [[libavcodec AAC\|Libav/FFmpeg pre-3.0 native AAC encoder]] (Multiplatform)		* [[libavcodec AAC\|Libav/FFmpeg pre-3.0 native AAC encoder]] (Multiplatform)
			** Use new FFmpeg encoder.
	* [[FAAC]]/[[FAAD]] (Multiplatform)		* [[FAAC]]/[[FAAD]] (Multiplatform)
	** Development appears stagnant, but the latest release is stable.		** Development appears stagnant, but the latest release is stable.
	* [https://gitlab.com/ecodis/exhale exhale] (xHE-AAC only, Multiplatform, experimental)

	=== Past ===		=== Past ===

Artoria2e5: /* Current */

2023-04-23T14:02:34Z

Current

← Older revision		Revision as of 14:02, 23 April 2023
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	* [[FAAC]]/[[FAAD]] (Multiplatform)		* [[FAAC]]/[[FAAD]] (Multiplatform)
	** Development appears stagnant, but the latest release is stable.		** Development appears stagnant, but the latest release is stable.
			* [https://gitlab.com/ecodis/exhale exhale] (xHE-AAC only, Multiplatform, experimental)

	=== Past ===		=== Past ===

Artoria2e5: /* Technologies used for compression */

2023-04-23T14:01:53Z

Technologies used for compression

← Older revision		Revision as of 14:01, 23 April 2023
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	* Perceptual Noise Substitution (PNS) – MPEG4 AAC only		* Perceptual Noise Substitution (PNS) – MPEG4 AAC only
	* Spectral Band Replication ([[SBR]]) – HE AAC		* Spectral Band Replication ([[SBR]]) – HE AAC
			** Enhanced SBR (eSBR) - USAC/xHE-AAC
	* [[Parametric stereo]] (PS) – HE AAC		* [[Parametric stereo]] (PS) – HE AAC
			** "MPEG" parametric surround - USAC/xHE-AAC
			* Algebraic code-excited linear prediction (ACELP)-like - USAC/xHE-AAC (speech-optimized method)

	== Encoders / Decoders (Supported Platforms) ==		== Encoders / Decoders (Supported Platforms) ==

Artoria2e5 at 13:58, 23 April 2023

2023-04-23T13:58:02Z

← Older revision		Revision as of 13:58, 23 April 2023
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	* Heavily patented		* Heavily patented
	* Increased complexity		* Increased complexity
	* ~~'''~~AAC~~'''~~ comes in different "flavors" (object types: '''AAC LC''', '''AAC HE''', '''AAC PS''' etc.). Many (especially portable) players only support LC (at the moment) so you can have files that are valid but your player won't play them or play at a reduced quality.		* AAC comes in different "flavors" (object types: '''AAC LC''', '''AAC HE''', '''AAC PS''' etc.). Many (especially portable) players only support LC (at the moment) so you can have files that are valid but your player won't play them or play at a reduced quality.

	== Technical Information ==		== Technical Information ==
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	* Modified Discrete Cosine Transform (I[[MDCT]])		* Modified Discrete Cosine Transform (I[[MDCT]])
	* Gain control and hybrid filter bank (polyphase quadrature filter (IPQF)+IMDCT)		* Gain control and hybrid filter bank (polyphase quadrature filter (IPQF)+IMDCT)
	* Long Term Prediction (LTP) – MPEG4 ~~'''~~AAC~~'''~~ only		* Long Term Prediction (LTP) – MPEG4 AAC only
	* Perceptual Noise Substitution (PNS) – MPEG4 ~~'''~~AAC~~'''~~ only		* Perceptual Noise Substitution (PNS) – MPEG4 AAC only
	* Spectral Band Replication ([[SBR]]) – HE ~~'''~~AAC~~'''~~		* Spectral Band Replication ([[SBR]]) – HE AAC
	* [[Parametric stereo]] (PS) – HE ~~'''~~AAC~~'''~~		* [[Parametric stereo]] (PS) – HE AAC

	== Encoders / Decoders (Supported Platforms) ==		== Encoders / Decoders (Supported Platforms) ==
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	== External References ==		== External References ==
	* [[AAC FAQ]]		* [[AAC FAQ]]
	* Read the [[AAC guide]] to learn how to obtain ~~'''~~AAC~~'''~~/[[MP4]] files out of WAV files and CDs.		* Read the [[AAC guide]] to learn how to obtain AAC/[[MP4]] files out of WAV files and CDs.
	* Detailed ~~'''~~AAC~~'''~~ comparisons can be found at Roberto's listening tests page.		* Detailed AAC comparisons can be found at Roberto's listening tests page.
	<references />		<references />

	[[Category:Codecs]]		[[Category:Codecs]]
	[[Category:Lossy]]		[[Category:Lossy]]

Artoria2e5: /* Technical Information */

2023-04-23T13:56:35Z

Technical Information

← Older revision		Revision as of 13:56, 23 April 2023
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	* MPEG-4 AAC HE / High Efficiency		* MPEG-4 AAC HE / High Efficiency
	* MPEG-4 AAC LD / Low Delay		* MPEG-4 AAC LD / Low Delay
			* USAC / Unified Speech and Audio Coding ["xHE-AAC" being a profile]

	Different Object Types vary in complexity. Some take longer to encode/decode as a result of the different complexities. Furthermore, the benefits of the more complex profiles are often not worth the CPU power required to encode/decode them. As a result the Low Complexity/LC Object Type has become the profile used by most encoders and supported by most decoders. However, the High Efficiency (HE) Object Type has become more popular recently with its addition to the Nero and Quicktime AAC encoder.		Different Object Types vary in complexity. Some take longer to encode/decode as a result of the different complexities. Furthermore, the benefits of the more complex profiles are often not worth the CPU power required to encode/decode them. As a result the Low Complexity/LC Object Type has become the profile used by most encoders and supported by most decoders. However, the High Efficiency (HE) Object Type has become more popular recently with its addition to the Nero and Quicktime AAC encoder.

Artoria2e5: /* Technical Information */

2023-04-23T13:54:19Z

Technical Information

← Older revision		Revision as of 13:54, 23 April 2023
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	== Technical Information ==		== Technical Information ==
	~~'''~~AAC~~'''~~ stands for 'Advanced Audio Coding' and is part of the [[MPEG-4]] Systems Standard. Originally known as MPEG-2 Non-Backwards Compatible (As apposed to MPEG-2 Backwards Compatible) it is the succesor to MPEG-1/2 Layer III ([[MP3]]). It uses the [[MP4]] [[container]] (which is based on Apple's [[MOV]] container) to store metadata (i.e. tag information).		AAC stands for 'Advanced Audio Coding' and is part of the [[MPEG-4]] Systems Standard. Originally known as MPEG-2 Non-Backwards Compatible (As apposed to MPEG-2 Backwards Compatible) it is the succesor to MPEG-1/2 Layer III ([[MP3]]). It uses the [[MP4]] [[container]] (which is based on Apple's [[MOV]] container) to store metadata (i.e. tag information).

	As part of the MPEG-4 Systems Standard, an ~~'''~~AAC~~'''~~ encoded file can include up to 48 full-bandwith audio channels (up to 96 kHz) and 15 Low Frequency Enhancement channels (limited to 120 Hz) plus 15 data streams.		As part of the MPEG-4 Systems Standard, an AAC encoded file can include up to 48 full-bandwith audio channels (up to 96 kHz) and 15 Low Frequency Enhancement channels (limited to 120 Hz) plus 15 data streams.

	~~'''~~AAC~~'''~~ encoding methods are organised into Profiles (MPEG-2) or Object Types (MPEG-4). These different Object Types are not necessarily compatible with each other and may not be playable with various decoders. Some of the various Object Types are:		AAC encoding methods are organised into Profiles (MPEG-2) or Object Types (MPEG-4). These different Object Types are not necessarily compatible with each other and may not be playable with various decoders. Some of the various Object Types are (see [https://en.wikipedia.org/wiki/MPEG-4_Part_3#MPEG-4_Audio_Object_Types Wikipedia] for a full list):

	* MPEG-2 AAC LC / Low Complexity		* MPEG-2 AAC LC / Low Complexity
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	* MPEG-4 AAC LD / Low Delay		* MPEG-4 AAC LD / Low Delay

	Different Object Types vary in complexity. Some take longer to encode/decode as a result of the different complexities. Furthermore, the benefits of the more complex profiles are often not worth the CPU power required to encode/decode them. As a result the Low Complexity/LC Object Type has become the profile used by most encoders and supported by most decoders. However, the High Efficiency (HE) Object Type has become more popular recently with its addition to the Nero and Quicktime ~~'''~~AAC~~'''~~ encoder.		Different Object Types vary in complexity. Some take longer to encode/decode as a result of the different complexities. Furthermore, the benefits of the more complex profiles are often not worth the CPU power required to encode/decode them. As a result the Low Complexity/LC Object Type has become the profile used by most encoders and supported by most decoders. However, the High Efficiency (HE) Object Type has become more popular recently with its addition to the Nero and Quicktime AAC encoder.

	Currently all players support the LC Object Type, although some will work on only MPEG2 or MPEG4 streams. Players based on the FAAD2 decoder (eg. [[foobar2000]], [[Winamp]] plugins) support almost all Object Types including HE ~~'''~~AAC~~'''~~. 3ivX also supports all Object Types except SSR.		Currently all players support the LC Object Type, although some will work on only MPEG2 or MPEG4 streams. Players based on the FAAD2 decoder (eg. [[foobar2000]], [[Winamp]] plugins) support almost all Object Types including HE AAC. 3ivX also supports all Object Types except SSR.

	== Technologies used for compression ==		== Technologies used for compression ==

Artoria2e5: /* Technologies used for compression */

2023-04-23T11:06:26Z

Technologies used for compression

← Older revision		Revision as of 11:06, 23 April 2023
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	* Perceptual Noise Substitution (PNS) – MPEG4 '''AAC''' only		* Perceptual Noise Substitution (PNS) – MPEG4 '''AAC''' only
	* Spectral Band Replication ([[SBR]]) – HE '''AAC'''		* Spectral Band Replication ([[SBR]]) – HE '''AAC'''
	* Parametric ~~Stereo~~ (PS) – HE '''AAC'''		* [[Parametric stereo]] (PS) – HE '''AAC'''

	== Encoders / Decoders (Supported Platforms) ==		== Encoders / Decoders (Supported Platforms) ==

Artoria2e5: /* Patent situation */

2023-04-23T11:03:00Z

Patent situation

← Older revision		Revision as of 11:03, 23 April 2023
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	== Patent situation ==		== Patent situation ==
	The owners of the AAC patent pool expects to charge a per-unit fee from codec makers.<ref>[https://www.sec.gov/Archives/edgar/data/1649009/000121390020023370/ea125930ex10-9_siyatamobile.htm "AAC PATENT LICENSE AGREEMENT"]</ref> In theory at least, compiling your own version of an encoder ''or'' decoder means you are "making" an unlicensed product. To this day very few people even care about this: FFmpeg happily links you to binary builds that contain its native decoder, capable of decoding even AAC-LD, which has a patent that lasts till 2030!<ref>See [https://hydrogenaud.io/index.php/topic,121109.0.html List of AAC related patents]</ref>		The owners of the AAC patent pool expects to charge a per-unit fee from codec makers.<ref>[https://www.sec.gov/Archives/edgar/data/1649009/000121390020023370/ea125930ex10-9_siyatamobile.htm "AAC PATENT LICENSE AGREEMENT"]</ref> In theory at least, compiling your own version of an encoder ''or'' decoder means you are "making" an unlicensed product. To this day very few people even care about this: FFmpeg happily links you to binary builds that contain its native decoder, capable of decoding even AAC-LD, which has a patent that lasts till 2030.<ref>See [https://hydrogenaud.io/index.php/topic,121109.0.html List of AAC related patents]</ref>

	== External References ==		== External References ==

Artoria2e5 at 11:01, 23 April 2023

2023-04-23T11:01:05Z

← Older revision		Revision as of 11:01, 23 April 2023
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	<br clear="right" />		<br clear="right" />

			== Patent situation ==
			The owners of the AAC patent pool expects to charge a per-unit fee from codec makers.<ref>[https://www.sec.gov/Archives/edgar/data/1649009/000121390020023370/ea125930ex10-9_siyatamobile.htm "AAC PATENT LICENSE AGREEMENT"]</ref> In theory at least, compiling your own version of an encoder ''or'' decoder means you are "making" an unlicensed product. To this day very few people even care about this: FFmpeg happily links you to binary builds that contain its native decoder, capable of decoding even AAC-LD, which has a patent that lasts till 2030!<ref>See [https://hydrogenaud.io/index.php/topic,121109.0.html List of AAC related patents]</ref>

	== External References ==		== External References ==
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	* Read the [[AAC guide]] to learn how to obtain '''AAC'''/[[MP4]] files out of WAV files and CDs.		* Read the [[AAC guide]] to learn how to obtain '''AAC'''/[[MP4]] files out of WAV files and CDs.
	* Detailed '''AAC''' comparisons can be found at Roberto's listening tests page.		* Detailed '''AAC''' comparisons can be found at Roberto's listening tests page.
			<references />

	[[Category:Codecs]]		[[Category:Codecs]]
	[[Category:Lossy]]		[[Category:Lossy]]

Artoria2e5: /* Introduction */ Don't do that heading

2023-04-21T14:34:49Z

Introduction: Don't do that heading

← Older revision		Revision as of 14:34, 21 April 2023
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	~~= Introduction =~~
	'''Advanced Audio Coding''' ('''AAC''') forms part of the latest specifications from the MPEG committee, and is their official successor to the popular [[MP3]] format. As with MP3, the AAC format is an international standard, and is backed by several big-name companies, including Dolby, Sony and Nokia.		'''Advanced Audio Coding''' ('''AAC''') forms part of the latest specifications from the MPEG committee, and is their official successor to the popular [[MP3]] format. As with MP3, the AAC format is an international standard, and is backed by several big-name companies, including Dolby, Sony and Nokia.