SpeechCodec » History » Version 5
laforge, 10/11/2019 12:27 PM
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2 | 4 | h1. Speech Codec |
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5 | 4 | The speech codec is a proprietary AMBE variant from "DVSI":http://www.dvsinc.com/. The official spec only contain a very rough overview and no technical information about the format and how to encode or decode it. |
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8 | 4 | h2. Patents |
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11 | The ETSI lists patents relevant to GMR. (See "here":http://ip5226084r.etsi.org/IPRDetails.aspx?IPRD_ID=151&IPRD_TYPE_ID=2&MODE=2). |
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13 | * "US5226084":http://www.google.com/patents?id=X-EfAAAAEBAJ&zoom=4&pg=PA1#v=onepage&q&f=false : Methods for speech quantization and error correction |
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14 | * "US5715365":http://www.google.com/patents?id=hv0iAAAAEBAJ&zoom=4&pg=PA1#v=onepage&q&f=false : Estimation of excitation parameters |
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15 | * "US5826222":http://www.google.com/patents?id=NW8YAAAAEBAJ&zoom=4&pg=PA1#v=onepage&q&f=false : Estimation of excitation parameters |
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16 | * "US5754974":http://www.google.com/patents?id=eqkjAAAAEBAJ&zoom=4&pg=PA5#v=onepage&q&f=false : Spectral magnitude representation for multi-band excitation speech coders |
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17 | * "US5701390":http://www.google.com/patents?id=4kMkAAAAEBAJ&zoom=4&pg=PA1#v=onepage&q&f=false : Synthesis of MBE-based coded speech using regenerated phase information |
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19 | 1 | This list is not really complete or accurate though. In particular it's missing the patent that has the most in common with the actual codec is (US&EU versions) : |
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21 | 4 | * "US6199037":http://www.google.com/patents/US6199037B1: Joint quantization of speech subframe voicing metrics and fundamental frequencies |
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22 | * "EP0927988B1":http://www.google.com/patents/EP0927988B1: Encoding speech |
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25 | h2. Implementation |
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28 | Osmocom-GMR contains a basic implementation of a voice decoder. Its quality is not as good as the official decoder but it does produce perfectly intelligible voice. You can find the implementation in the src/codec directory of the git. |