FreeCalypso > hg > gsm-codec-lib
annotate doc/AMR-EFR-conversion @ 256:a33edf624061
libgsmfr2: start with API definition and port of libgsmfrp code
| author | Mychaela Falconia <falcon@freecalypso.org> |
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| date | Fri, 12 Apr 2024 20:49:53 +0000 |
| parents | 8eb0e7a39409 |
| children | 78739fda2856 |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
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changeset
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1 We have two simple utilities that allow one to experiment with "dumb" bit- |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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2 shuffling conversion between AMR 12k2 and EFR codec formats, to explore |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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3 capabilities and limitations of this approach. |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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4 |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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5 gsm-amr2efr reads an AMR speech recording in RFC 4867 storage format (the common |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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6 .amr format) and converts it to EFR in gsmx format. The AMR input to this |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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7 utility must consists of MR122 frames only - no other AMR modes, no SID and no |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
8 NO_DATA gaps. The intent is that one can take a starting speech sample in WAV |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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9 format, encode it into AMR with amrnb-enc from opencore-amrnb (by default that |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
10 utility produces MR122 encoding without DTX), and then convert the AMR output to |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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11 EFR with gsm-amr2efr. One can then encode the same starting-point WAV speech |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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12 sample with gsmefr-encode (matching official EFR from ETSI) and compare the two |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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13 EFR outputs. When you do this experiment, you will see that the two EFR outputs |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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14 will be different (you can then analyze encoded speech parameter diffs with |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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15 gsmrec-dump), but each version can be fed to an EFR decoder, resulting in |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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16 OK-sounding speech. |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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17 |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
18 gsm-efr2amr performs the opposite conversion: it reads an EFR session recording |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
19 in gsmx format and converts it to AMR storage format. The input to gsm-efr2amr |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
20 is allowed to contain Themyscira BFI markers in addition to EFR frames; these |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
21 BFI markers will be turned into AMR NO_DATA frames. The same input can also |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
22 contain EFR SID frames - however, gsm-efr2amr will not detect them and won't |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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23 give them any special handling, instead they will be bit-reshuffled into MR122 |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
24 just like EFR speech frames. The result of such "dumb" conversion is invalid |
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8eb0e7a39409
doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
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25 AMR, and when you decode it with amrnb-dec, you will hear some strange noises. |