FreeCalypso > hg > gsm-codec-lib

annotate doc/AMR-EFR-conversion @ 173:aaa0380f9958

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
doc/RTP-analysis: document new tools
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 27 Dec 2022 00:00:57 +0000
parents 8eb0e7a39409
children 78739fda2856
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
136
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
1 We have two simple utilities that allow one to experiment with "dumb" bit-
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
2 shuffling conversion between AMR 12k2 and EFR codec formats, to explore
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
3 capabilities and limitations of this approach.
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
4
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
5 gsm-amr2efr reads an AMR speech recording in RFC 4867 storage format (the common
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
6 .amr format) and converts it to EFR in gsmx format. The AMR input to this
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
7 utility must consists of MR122 frames only - no other AMR modes, no SID and no
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
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
9 format, encode it into AMR with amrnb-enc from opencore-amrnb (by default that
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
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
11 EFR with gsm-amr2efr. One can then encode the same starting-point WAV speech
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
12 sample with gsmefr-encode (matching official EFR from ETSI) and compare the two
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
13 EFR outputs. When you do this experiment, you will see that the two EFR outputs
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
14 will be different (you can then analyze encoded speech parameter diffs with
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
15 gsmrec-dump), but each version can be fed to an EFR decoder, resulting in
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
16 OK-sounding speech.
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
17
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
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
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
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
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
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
23 give them any special handling, instead they will be bit-reshuffled into MR122
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
8eb0e7a39409 doc: document command line utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
25 AMR, and when you decode it with amrnb-dec, you will hear some strange noises.