Spectral band replication (SBR) is a technology to enhance audio or speech codecs, especially at low bit rates and is based on harmonic redundancy in the frequency domain.
Spectrogram of this recording of a violin playing. Note the harmonics occurring at whole-number multiples of the fundamental frequency. SBR exploits this redundancy.
It can be combined with any audio compression codec: the codec itself transmits the lower and midfrequencies of the spectrum, while SBR replicates higher frequency content by transposing up harmonics from the lower and midfrequencies at the decoder.[1] Some guidance information for reconstruction of the high-frequency spectral envelope is transmitted as side information.
When needed, it also reconstructs or adaptively mixes in noise-like information in selected frequency bands in order to faithfully replicate signals that originally contained no or fewer tonal components.
The SBR idea is based on the principle that the psychoacoustic part of the human brain tends to analyse higher frequencies with less accuracy; thus harmonic phenomena associated with the spectral band replication process needs only be accurate in a perceptual sense and not technically or mathematically exact.
A Swedish company Coding Technologies (acquired by Dolby in 2007) developed and pioneered the use of SBR in its MPEG-2 AAC-derived codec called aacPlus, which first appeared in 2001. This codec was submitted to MPEG and formed the basis of MPEG-4 High-Efficiency AAC (HE-AAC), standardized in 2003.[2]Lars Liljeryd, Kristofer Kjörling, and Martin Dietz received the IEEE Masaru Ibuka Consumer Electronics Award in 2013 for their work developing and marketing HE-AAC.[3][4] Coding Technologies' SBR method has also been used with WMA 10 Professional to create WMA 10 Pro LBR, and with MP3 to create mp3PRO.
If the player is not capable of using the side information that has been transmitted alongside the "normal" compressed audio data, it may still be able to play the "baseband" data (e.g. sampled at 22.05 kHz instead of 44.1 kHz) as usual, resulting in a dull (since the high frequencies are missing), but otherwise mostly acceptable sound. This is, for example, the case if an mp3PRO file is played back with MP3 software incapable of utilizing the SBR information.
Opus's CELT part performs spectral folding on the MDCT bin level, making it a far less advanced but lower-delay technique compared to SBR.[6]
Dolby Digital Plus (E-AC3) performs Spectral Extension (SPX). SPX reduces high-frequency components to metadata and is similar to E-AC3 multichannel coupling calculation.[7]Dolby AC-4 expands the technique to Advanced Spectral Extension (A-SPX), with the option of interleaving with regular, non-extended data in time or frequency domain. As a result, SPX can be selective disabled for difficult portions.[8]
Methodsedit
Encoding of SBR produces a downsampled (usually 2:1) audio signal and guidance information. In an early publication, the guiding data is described as being produced by quadrature mirror filter (QMF) analysis and an envelope estimator.[9]
A traditional approach starts with small intervals of discrete fourier transform (DFT), phase adjustments, IDFT, and ends with overlap-add. This method is sensitive to transient signals which can cause echos, requiring some padding (50% in USAC) in the DFT.
A newer approach is the QMF. One single filter bank can perform a whole time-stretch and pitch-scale operation for lower computational complexity.
^"Interview with Martin Dietz, Kristofer Kjörling, and Lars Liljeryd". YouTube. Retrieved 7 July 2015.
^. Archived from the original on November 15, 2006. Retrieved February 8, 2010.
^Jean-Marc Valin; Gregory Maxwell; Timothy B. Terriberry; Koen Vos (October 17–20, 2013). (PDF). www.xiph.org. New York, NY: Xiph.Org Foundation. p. 2. Archived from the original (PDF) on 14 July 2018. Retrieved 19 August 2014.
^Andersen, Robert Loring; Crockett, B.; Davidson, G.; Davis, Mark; Fielder, L.; Turner, Stephen C.; Vinton, M.; Williams, P. (1 October 2004). (PDF). Journal of The Audio Engineering Society.
^"Dolby® AC-4: Audio delivery for next-generation entertainment services" (PDF).
^Ekstrand, Per (November 2022). "Bandwidth extension of audio signals by spectral band replication" (PDF). Proc.1st IEEE Benelux Workshop on Model based Processing and Coding of Audio (MPCA-2002), Leuven, Belgium.
^Zhong, Haishan; Villemoes, Lars; Ekstrand, Per; Disch, Sascha; Nagel, Frederik; Wilde, Stephan; Chong, Kok Seng; Norimatsu, Takeshi (19 October 2011). "QMF Based Harmonic Spectral Band Replication". Audio Engineering Society.
This sound technology article is a stub. You can help Wikipedia by expanding it.
spectral, band, replication, technology, enhance, audio, speech, codecs, especially, rates, based, harmonic, redundancy, frequency, domain, spectrogram, this, recording, violin, playing, note, harmonics, occurring, whole, number, multiples, fundamental, freque. Spectral band replication SBR is a technology to enhance audio or speech codecs especially at low bit rates and is based on harmonic redundancy in the frequency domain Spectrogram of this recording of a violin playing Note the harmonics occurring at whole number multiples of the fundamental frequency SBR exploits this redundancy It can be combined with any audio compression codec the codec itself transmits the lower and midfrequencies of the spectrum while SBR replicates higher frequency content by transposing up harmonics from the lower and midfrequencies at the decoder 1 Some guidance information for reconstruction of the high frequency spectral envelope is transmitted as side information When needed it also reconstructs or adaptively mixes in noise like information in selected frequency bands in order to faithfully replicate signals that originally contained no or fewer tonal components The SBR idea is based on the principle that the psychoacoustic part of the human brain tends to analyse higher frequencies with less accuracy thus harmonic phenomena associated with the spectral band replication process needs only be accurate in a perceptual sense and not technically or mathematically exact Contents 1 History and use 2 Methods 3 See also 4 External links 5 ReferencesHistory and use editA Swedish company Coding Technologies acquired by Dolby in 2007 developed and pioneered the use of SBR in its MPEG 2 AAC derived codec called aacPlus which first appeared in 2001 This codec was submitted to MPEG and formed the basis of MPEG 4 High Efficiency AAC HE AAC standardized in 2003 2 Lars Liljeryd Kristofer Kjorling and Martin Dietz received the IEEE Masaru Ibuka Consumer Electronics Award in 2013 for their work developing and marketing HE AAC 3 4 Coding Technologies SBR method has also been used with WMA 10 Professional to create WMA 10 Pro LBR and with MP3 to create mp3PRO HE AAC which uses SBR is used in broadcast systems like DAB Digital Radio Mondiale including xHE AAC HD Radio and XM Satellite Radio 5 If the player is not capable of using the side information that has been transmitted alongside the normal compressed audio data it may still be able to play the baseband data e g sampled at 22 05 kHz instead of 44 1 kHz as usual resulting in a dull since the high frequencies are missing but otherwise mostly acceptable sound This is for example the case if an mp3PRO file is played back with MP3 software incapable of utilizing the SBR information Opus s CELT part performs spectral folding on the MDCT bin level making it a far less advanced but lower delay technique compared to SBR 6 Dolby Digital Plus E AC3 performs Spectral Extension SPX SPX reduces high frequency components to metadata and is similar to E AC3 multichannel coupling calculation 7 Dolby AC 4 expands the technique to Advanced Spectral Extension A SPX with the option of interleaving with regular non extended data in time or frequency domain As a result SPX can be selective disabled for difficult portions 8 Methods editEncoding of SBR produces a downsampled usually 2 1 audio signal and guidance information In an early publication the guiding data is described as being produced by quadrature mirror filter QMF analysis and an envelope estimator 9 Decoding of SBR requires transposing harmonics a case of audio time stretching and pitch scaling 10 A traditional approach starts with small intervals of discrete fourier transform DFT phase adjustments IDFT and ends with overlap add This method is sensitive to transient signals which can cause echos requiring some padding 50 in USAC in the DFT A newer approach is the QMF One single filter bank can perform a whole time stretch and pitch scale operation for lower computational complexity See also editMPEG 4 Part 3 Psychoacoustics Spectral bandsExternal links editSBR explained at the Wayback Machine archived 2014 12 27 Coding Technologies page describing SBR as it appeared in 2007 at the Dolby acquisitionReferences edit Novak Clark Spectral Band Replication and aacPlus Coding An Overview PDF Archived from the original PDF on November 30 2010 Retrieved February 8 2010 ISO 2003 Bandwidth extension ISO IEC 14496 3 2001 Amd 1 2003 ISO Retrieved 2009 10 13 IEEE Masaru Ibuka Consumer Electronics Award IEEE org Retrieved 7 July 2015 Interview with Martin Dietz Kristofer Kjorling and Lars Liljeryd YouTube Retrieved 7 July 2015 XM Radio Fast Facts Archived from the original on November 15 2006 Retrieved February 8 2010 Jean Marc Valin Gregory Maxwell Timothy B Terriberry Koen Vos October 17 20 2013 High Quality Low Delay Music Coding in the Opus Codec PDF www xiph org New York NY Xiph Org Foundation p 2 Archived from the original PDF on 14 July 2018 Retrieved 19 August 2014 Andersen Robert Loring Crockett B Davidson G Davis Mark Fielder L Turner Stephen C Vinton M Williams P 1 October 2004 Introduction to Dolby Digital Plus an Enhancement to the Dolby Digital Coding System PDF Journal of The Audio Engineering Society Dolby AC 4 Audio delivery for next generation entertainment services PDF Ekstrand Per November 2022 Bandwidth extension of audio signals by spectral band replication PDF Proc 1st IEEE Benelux Workshop on Model based Processing and Coding of Audio MPCA 2002 Leuven Belgium Zhong Haishan Villemoes Lars Ekstrand Per Disch Sascha Nagel Frederik Wilde Stephan Chong Kok Seng Norimatsu Takeshi 19 October 2011 QMF Based Harmonic Spectral Band Replication Audio Engineering Society nbsp This sound technology article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Spectral band replication amp oldid 1218232779, wikipedia, wiki, book, books, library,
