Parametric stereo (abbreviated as PS)[1] is an audio compression algorithm used as an audio coding format for digital audio. It is considered an Audio Object Type of MPEG-4 Part 3 (MPEG-4 Audio) that serves to enhance the coding efficiency of low bandwidth stereo audio media. Parametric Stereo digitally codes a stereo audio signal by storing the audio as monaural alongside a small amount of extra information. This extra information (defined as "parametric overhead") describes how the monaural signal will behave across both stereo channels, which allows for the signal to exist in true stereo upon playback.
Advanced Audio Coding Low Complexity (AAC LC) combined with Spectral Band Replication (SBR) and Parametric Stereo (PS) was defined as HE-AAC v2. An HE-AAC v1 decoder will only give mono sound when decoding an HE-AAC v2 bitstream. Parametric Stereo performs sparse coding in the spatial domain, somewhat similar to what SBR does in the frequency domain. An AAC HE v2 bitstream is obtained by downmixing the stereo audio to mono at the encoder along with 2–3 kbit/s of side info (the Parametric Stereo information) in order to describe the spatial intensity stereo generation and ambience regeneration at the decoder. By having the Parametric Stereo side info along with the mono audio stream, the decoder (player) can regenerate a faithful spatial approximation of the original stereo panorama at very low bitrates. Because only one audio channel is transmitted, along with the parametric side info, a 24 kbit/s coded audio signal with Parametric Stereo will be substantially improved in quality relative to discrete stereo audio signals encoded with conventional means. The additional bitrate spent on the single mono channel (combined with some PS side info) will substantially improve the perceived quality of the audio compared to a standard stereo stream at similar bitrate. However, this technique is only useful at the lowest bitrates (approx. 16–48 kbit/s and down to 14.4 kbps in xHE-AAC used in DRM) to give a good stereo impression, so while it can improve perceived quality at very low bitrates, it generally does not achieve transparency, since simulating the stereo dynamics of the audio with the technique is limited and generally deteriorates perceived quality regardless of the bitrate.
Developmentedit
The development of Parametric Stereo was as a result of necessity to further enhance the coding efficiency of audio in low bandwidth stereo media. It has gone through various iterations and improvements, however, it was first standardized as an algorithm when included in the feature set of MPEG-4 Audio.[1] Parametric Stereo was originally developed in Stockholm, Sweden by companies Philips and Coding Technologies, and was first unveiled in Naples, Italy, in 2004 during the 7th International Conference on Digital Audio Effects (DAFx'04).[2]
Approachesedit
The implementation in MPEG-4 is based on specifying the relative amount, delay, and correlation (coherence) of left and right channels by each frequency band in the mixed mono audio. Special handling is given to transient signals, as the approach would otherwise cause unacceptable delays. Compared to intensity stereo coding, which does not record delay or correlation, PS can provide more ambience.[2]
Modifications to PS continue to be proposed.
An 2006 conference report describes ways to mitigate the loss of amplitude in downmixing.[3]
^ abBreebaart, Jeroen; Par, Steven; Kohlrausch, Armin; Schuijers, Erik (2005-06-01). "Parametric Coding of Stereo Audio". EURASIP Journal on Advances in Signal Processing. 2005 (9): 561917. Bibcode:2005EJASP2005..284B. doi:10.1155/ASP.2005.1305.
^ abPurnhagen, Heiko (October 5–8, 2004). "LOW COMPLEXITY PARAMETRIC STEREO CODING IN MPEG-4" (PDF). 7th International Conference on Digital Audio Effects: 163–168.
^Jimmy Lapierre; R. Lefebvre (2006). On Improving Parametric Stereo Audio Coding. AES 120th Convention, Paris, France.
^Pang, Hee-Suk (5 October 2009). "Pilot-Based Coding Scheme for Parametric Stereo in Enhanced aacPlus". ETRI Journal. 31 (5): 613–615. doi:10.4218/etrij.09.0209.0193. S2CID 61177149.
^Elfitri, Ikhwana; Kurnia, Rahmadi; Harneldi, Defry (October 2014). Experimental study on improved parametric stereo for bit rate scalable audio coding(PDF). 2014 6th International Conference on Information Technology and Electrical Engineering (ICITEE). pp. 1–5. doi:10.1109/ICITEED.2014.7007922.
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This article has multiple issues Please help improve it or discuss these issues on the talk page Learn how and when to remove these template messages This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Parametric stereo news newspapers books scholar JSTOR April 2022 Learn how and when to remove this message The topic of this article may not meet Wikipedia s general notability guideline Please help to demonstrate the notability of the topic by citing reliable secondary sources that are independent of the topic and provide significant coverage of it beyond a mere trivial mention If notability cannot be shown the article is likely to be merged redirected or deleted Find sources Parametric stereo news newspapers books scholar JSTOR September 2021 Learn how and when to remove this message This article may be too technical for most readers to understand Please help improve it to make it understandable to non experts without removing the technical details September 2021 Learn how and when to remove this message Learn how and when to remove this message Parametric stereo abbreviated as PS 1 is an audio compression algorithm used as an audio coding format for digital audio It is considered an Audio Object Type of MPEG 4 Part 3 MPEG 4 Audio that serves to enhance the coding efficiency of low bandwidth stereo audio media Parametric Stereo digitally codes a stereo audio signal by storing the audio as monaural alongside a small amount of extra information This extra information defined as parametric overhead describes how the monaural signal will behave across both stereo channels which allows for the signal to exist in true stereo upon playback Contents 1 History 1 1 Background 1 2 Development 2 Approaches 3 See also 4 ReferencesHistory editBackground edit Advanced Audio Coding Low Complexity AAC LC combined with Spectral Band Replication SBR and Parametric Stereo PS was defined as HE AAC v2 An HE AAC v1 decoder will only give mono sound when decoding an HE AAC v2 bitstream Parametric Stereo performs sparse coding in the spatial domain somewhat similar to what SBR does in the frequency domain An AAC HE v2 bitstream is obtained by downmixing the stereo audio to mono at the encoder along with 2 3 kbit s of side info the Parametric Stereo information in order to describe the spatial intensity stereo generation and ambience regeneration at the decoder By having the Parametric Stereo side info along with the mono audio stream the decoder player can regenerate a faithful spatial approximation of the original stereo panorama at very low bitrates Because only one audio channel is transmitted along with the parametric side info a 24 kbit s coded audio signal with Parametric Stereo will be substantially improved in quality relative to discrete stereo audio signals encoded with conventional means The additional bitrate spent on the single mono channel combined with some PS side info will substantially improve the perceived quality of the audio compared to a standard stereo stream at similar bitrate However this technique is only useful at the lowest bitrates approx 16 48 kbit s and down to 14 4 kbps in xHE AAC used in DRM to give a good stereo impression so while it can improve perceived quality at very low bitrates it generally does not achieve transparency since simulating the stereo dynamics of the audio with the technique is limited and generally deteriorates perceived quality regardless of the bitrate Development edit The development of Parametric Stereo was as a result of necessity to further enhance the coding efficiency of audio in low bandwidth stereo media It has gone through various iterations and improvements however it was first standardized as an algorithm when included in the feature set of MPEG 4 Audio 1 Parametric Stereo was originally developed in Stockholm Sweden by companies Philips and Coding Technologies and was first unveiled in Naples Italy in 2004 during the 7th International Conference on Digital Audio Effects DAFx 04 2 Approaches editThe implementation in MPEG 4 is based on specifying the relative amount delay and correlation coherence of left and right channels by each frequency band in the mixed mono audio Special handling is given to transient signals as the approach would otherwise cause unacceptable delays Compared to intensity stereo coding which does not record delay or correlation PS can provide more ambience 2 Modifications to PS continue to be proposed An 2006 conference report describes ways to mitigate the loss of amplitude in downmixing 3 A 2009 paper adds pilot based coding to PS 4 An 2011 conference paper describes the use of additional residual information to record and eliminate PS artifacts 5 MPEG Surround uses a technique related to PS See also editMPEG 4 Part 3References edit a b Breebaart Jeroen Par Steven Kohlrausch Armin Schuijers Erik 2005 06 01 Parametric Coding of Stereo Audio EURASIP Journal on Advances in Signal Processing 2005 9 561917 Bibcode 2005EJASP2005 284B doi 10 1155 ASP 2005 1305 a b Purnhagen Heiko October 5 8 2004 LOW COMPLEXITY PARAMETRIC STEREO CODING IN MPEG 4 PDF 7th International Conference on Digital Audio Effects 163 168 Jimmy Lapierre R Lefebvre 2006 On Improving Parametric Stereo Audio Coding AES 120th Convention Paris France Pang Hee Suk 5 October 2009 Pilot Based Coding Scheme for Parametric Stereo in Enhanced aacPlus ETRI Journal 31 5 613 615 doi 10 4218 etrij 09 0209 0193 S2CID 61177149 Elfitri Ikhwana Kurnia Rahmadi Harneldi Defry October 2014 Experimental study on improved parametric stereo for bit rate scalable audio coding PDF 2014 6th International Conference on Information Technology and Electrical Engineering ICITEE pp 1 5 doi 10 1109 ICITEED 2014 7007922 nbsp This sound technology article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w 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