This article's lead sectionmay be too short to adequately summarize the key points. Please consider expanding the lead to provide an accessible overview of all important aspects of the article.(January 2011)
In 1967 Osamu Fujimura (MIT) showed basic advantages of the multi-band representation of speech ("An Approximation to Voice Aperiodicity", IEEE 1968). This work gave a start to development of the "multi-band excitation" method of speech coding, that was patented in 1997 (now expired) by founders of DVSI as "Multi-Band Excitation" (MBE). All consequent improvements known as Improved Multi-Band Excitation (IMBE), Advanced Multiband Excitation (AMBE), AMBE+ and AMBE+2 are based on this MBE method.
AMBE is a codebook-based vocoder that operates at bitrates of between 2 and 9.6 kbit/s, and at a sampling rate of 8 kHz in 20-ms frames. The audio data is usually combined with up to 7 bit/s[citation needed] of forward error correction data, producing a total RF bandwidth of approximately 2,250 Hz (compared to 2,700–3,000 Hz for an analogue single sideband transmission). Lost frames can be masked by using the parameters of the previous frame to fill in the gap.
AMBE is used in D-STARamateur radio digital voice communications. It has met criticism from the amateur radio community because the nature of its patent[1] and licensing runs counter to the openness of amateur radio, as well as usage restriction for being "undisclosed digital code" under FCC rule 97.309(b) and similar national legislation.[2]
System Fusion, open specification from Yaesu, also uses AMBE codec with C4FM modulation.
The NXDN digital voice and data protocol uses the AMBE+2 codec. NXDN is implemented by Icom in the IDAS system and by Kenwood as NEXEDGE.
APCO Project 25 Phase 2 trunked radio systems also use the AMBE+2 codec, while older Phase 1 radios such as the Motorola XTL and XTS series use the earlier IMBE codec. Newer Phase 1 capable radios such as the APX series radios use the AMBE+2 codec, which is backwards compatible with Phase 1.
Use of the AMBE standard requires a license from Digital Voice Systems, Inc. While a licensing fee is due for most codecs, DVSI does not disclose software licensing terms. Anecdotal evidence [citation needed] suggests that licensing fee begin from between $100,000 to $1 million. For purposes of comparison, licensing fees for use of the MP3 standard started at $15,000. For small-scale use and prototyping, the only option is to purchase a dedicated hardware IC from DVSI. These ICs can be purchased for less than $100 in small quantities.[3]
DSP Innovations Inc. offers a software implementation of APCO P25 Phase 1 (Full-Rate) and Phase 2 (Half-Rate) codecs as well as DMR and dPMR codecs. A technology licence from DVSI is required. The patent for IMBE has expired.
Alternativesedit
Codec2 is an open source alternative which uses half of the bandwidth of AMBE to encode speech of similar quality, [citation needed] created by David Rowe and lobbied by Bruce Perens. Codec2 still continues to evolve, with additional "modes" being developed, refined and made available on a continuous basis. This has resulted in an open source codec that has progressively increased its robustness and performance – when subjected to some of the most challenging RF and acoustic environments.[4]
Referencesedit
^US 6199037, John C. Hardwick, "Joint quantization of speech subframe voicing metrics and fundamental frequencies", issued 2001-03-06, assigned to Digital Voice Systems Inc
^David Rowe. "The Codec2 Project: Next-Generation Audio Codecs and Vocoders for Two-Way Radio". Retrieved 16 February 2012.
^"DVSI Pricing Information". dvsinc.com. Retrieved 8 April 2020.
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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 s lead section may be too short to adequately summarize the key points Please consider expanding the lead to provide an accessible overview of all important aspects of the article January 2011 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 Multi Band Excitation news newspapers books scholar JSTOR January 2011 Learn how and when to remove this message Learn how and when to remove this message Multi Band Excitation MBE is a series of proprietary speech coding standards developed by Digital Voice Systems Inc DVSI Contents 1 Overview 2 Usage 3 Licensing 4 Alternatives 5 References 6 External linksOverview editIn 1967 Osamu Fujimura MIT showed basic advantages of the multi band representation of speech An Approximation to Voice Aperiodicity IEEE 1968 This work gave a start to development of the multi band excitation method of speech coding that was patented in 1997 now expired by founders of DVSI as Multi Band Excitation MBE All consequent improvements known as Improved Multi Band Excitation IMBE Advanced Multiband Excitation AMBE AMBE and AMBE 2 are based on this MBE method AMBE is a codebook based vocoder that operates at bitrates of between 2 and 9 6 kbit s and at a sampling rate of 8 kHz in 20 ms frames The audio data is usually combined with up to 7 bit s citation needed of forward error correction data producing a total RF bandwidth of approximately 2 250 Hz compared to 2 700 3 000 Hz for an analogue single sideband transmission Lost frames can be masked by using the parameters of the previous frame to fill in the gap Usage editAMBE is used by the Inmarsat and Iridium satellite telephony systems and certain channels on XM Satellite Radio and is the speech coder for OpenSky Trunked radio systems AMBE is used in D STAR amateur radio digital voice communications It has met criticism from the amateur radio community because the nature of its patent 1 and licensing runs counter to the openness of amateur radio as well as usage restriction for being undisclosed digital code under FCC rule 97 309 b and similar national legislation 2 System Fusion open specification from Yaesu also uses AMBE codec with C4FM modulation The NXDN digital voice and data protocol uses the AMBE 2 codec NXDN is implemented by Icom in the IDAS system and by Kenwood as NEXEDGE APCO Project 25 Phase 2 trunked radio systems also use the AMBE 2 codec while older Phase 1 radios such as the Motorola XTL and XTS series use the earlier IMBE codec Newer Phase 1 capable radios such as the APX series radios use the AMBE 2 codec which is backwards compatible with Phase 1 Digital Mobile Radio DMR and Motorola s MOTOTRBO use the AMBE 2 codec Licensing editUse of the AMBE standard requires a license from Digital Voice Systems Inc While a licensing fee is due for most codecs DVSI does not disclose software licensing terms Anecdotal evidence citation needed suggests that licensing fee begin from between 100 000 to 1 million For purposes of comparison licensing fees for use of the MP3 standard started at 15 000 For small scale use and prototyping the only option is to purchase a dedicated hardware IC from DVSI These ICs can be purchased for less than 100 in small quantities 3 DSP Innovations Inc offers a software implementation of APCO P25 Phase 1 Full Rate and Phase 2 Half Rate codecs as well as DMR and dPMR codecs A technology licence from DVSI is required The patent for IMBE has expired Alternatives editCodec2 is an open source alternative which uses half of the bandwidth of AMBE to encode speech of similar quality citation needed created by David Rowe and lobbied by Bruce Perens Codec2 still continues to evolve with additional modes being developed refined and made available on a continuous basis This has resulted in an open source codec that has progressively increased its robustness and performance when subjected to some of the most challenging RF and acoustic environments 4 References edit US 6199037 John C Hardwick Joint quantization of speech subframe voicing metrics and fundamental frequencies issued 2001 03 06 assigned to Digital Voice Systems Inc David Rowe The Codec2 Project Next Generation Audio Codecs and Vocoders for Two Way Radio Retrieved 16 February 2012 DVSI Pricing Information dvsinc com Retrieved 8 April 2020 Bruce Perens Codec2 Retrieved 9 May 2012 External links edithttps web archive org web 20061017004427 http www dvsinc com products software htm http www dspini com dspini imbe htm Retrieved from https en wikipedia org w index php title Multi Band Excitation amp oldid 1170419222, wikipedia, wiki, book, books, library,
