Mercurial > hg > audiostuff
annotate spandsp-0.0.6pre17/DueDiligence @ 6:22a74b01a099 default tip
implement more meaningful test program
| author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
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| date | Fri, 25 Jun 2010 16:14:50 +0200 |
| parents | 26cd8f1ef0b1 |
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| rev | line source |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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1 Intellectual Property Due Diligence |
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2 ----------------------------------- |
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3 |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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4 Modems and voice coding are heavily patented areas. Implementing these without |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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5 serious consideration of IP issues would be foolish. This document describes |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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6 the basis on which the software has been implemented. |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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7 |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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8 |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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9 A check of the intellectual property information at the ITU web site shows a |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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10 number of patent claims against the current standards implemented by spandsp. |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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11 It is important to realise, however, that some of these patents have long |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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12 since expired (group III fax dates back to the 1970s). Also, many are |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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13 related to recent additions to the FAX standard, such as colour FAX handling, |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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14 which few people ever use. |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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15 |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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16 The V.14 rate adaption standard seems free of patent encumberance. |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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17 |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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18 One patent is listed as relevant to the V.17 standard. It is a patent from |
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26cd8f1ef0b1
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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19 IBM, but the ITU database does not specify its nature. I believe it is |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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20 related to the trellis coding used, and I think it has expired. I do not |
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26cd8f1ef0b1
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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21 know for sure. The techniques used in the implementation should be free of |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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22 patent encumberance. Most of the implementation is similar to the V.29 |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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23 modem. The key addition the trellis code processing. The trellis encoding |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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24 is trivial. The decoding uses Viterbi techniques, which are quite old. |
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26cd8f1ef0b1
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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25 |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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26 The V.21 standard dates from the 1950s. The V.23 standard is also very old. |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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27 There is no possibility that any patents related to it are still in force. |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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28 However, the implementation also needs to be free of patented techniques. |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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29 The implementation only uses very mature numerical oscillator and quadrature |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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30 correlation techniques, so there should be no patent issues. |
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26cd8f1ef0b1
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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31 |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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32 Only one patent is listed as relevant to the V.29 standard. This dates from |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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33 the 1970s, and must have expired. The modem has been implemented using only |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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34 very mature techniques, none of which can be less than 20 years old. There |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
parents:
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35 seem no possibility, therefore, that any patents are still in force related |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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36 to the techniques used. |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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37 |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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38 Some aspect of the V.8 standard seems to have patents associated with it, |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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39 according to the ITU patent database. I am unclear what these are. V.8 is a |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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40 very simple standard. There seems to be nothing innovative about it. |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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41 |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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42 Many patents are listed as relevant to the T.30 standard. However, they all |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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43 appear to relate to newer features, such as colour FAX, added in recent years. |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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44 The current implementation only covers the original features from the late |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
parents:
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45 1970s, where there appear to be patent issues. |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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46 |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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47 The T.4 standard defines the image compression and decompression techniques |
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26cd8f1ef0b1
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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48 used for group 3 FAXes. The spandsp implementation is based on code derived |
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26cd8f1ef0b1
import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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49 from freely available implementations of T.4. These have existed for a number |
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import spandsp-0.0.6pre17
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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50 of years without IP issues. The standard is old enough for any patents to have |
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26cd8f1ef0b1
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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51 expired, anyway. |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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52 |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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53 V.42bis compression uses the LZW algorithm. This is the same algorithm used in |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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54 GIF files. Unisys patented this algorithm. However, the Unisys patent has now |
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Peter Meerwald <pmeerw@cosy.sbg.ac.at>
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55 expired. |