FreeCalypso > hg > gsm-codec-lib
comparison doc/Codec-utils @ 136:8eb0e7a39409
doc: document command line utilities
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Sun, 11 Dec 2022 22:20:36 +0000 |
| parents | |
| children | 30c7bc064218 |
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| 135:22601ae99434 | 136:8eb0e7a39409 |
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| 1 Standalone command line utilities for FR and EFR codecs | |
| 2 ======================================================= | |
| 3 | |
| 4 The pre-existing FOSS opencore-amr package includes amrnb-enc and amrnb-dec test | |
| 5 programs: the first reads linear PCM from a WAV file and emits AMR encoder | |
| 6 output in a .amr file (RFC 4867 AMR storage format), the second reads this .amr | |
| 7 format and emits AMR decoder output as WAV. Inspired by these simple test | |
| 8 programs, the present package offers equivalent command line utilities for GSM | |
| 9 FR and EFR codecs. Here they are: | |
| 10 | |
| 11 gsmfr-encode This utility reads linear PCM from a WAV file, runs libgsm | |
| 12 06.10 encoder and writes the output in the classic .gsm format | |
| 13 (directly abutted FR codec frames of 33 bytes each). We don't | |
| 14 currently have a Tx-side DTX implementation (VAD etc) for GSM | |
| 15 FR, hence the output from gsmfr-encode will always consist of | |
| 16 good speech frames only. | |
| 17 | |
| 18 gsmfr-decode This utility reads our gsmx format (see Binary-file-format | |
| 19 article), which is a superset of the classic libgsm format. | |
| 20 The input to gsmfr-decode may be a pure .gsm recording as | |
| 21 produced by gsmfr-encode or toast from libgsm package, or it | |
| 22 can also contain SID frames and/or BFI markers. The processing | |
| 23 performed by gsmfr-decode begins with our FR1 Rx DTX handler | |
| 24 preprocessor, which will be an identity transform for pure .gsm | |
| 25 input but becomes important for real-world input containing SIDs | |
| 26 and BFIs, and is followed by gsm_decode() from libgsm. The | |
| 27 decoded output is written as WAV. | |
| 28 | |
| 29 gsmefr-encode This utility reads linear PCM from a WAV file, runs our EFR | |
| 30 encoder (Themyscira libgsmefr) and writes the output in our gsmx | |
| 31 format. There is an option to enable or disable DTX: -d enables | |
| 32 DTX, otherwise it is disabled. (This option mirrors amrnb-enc.) | |
| 33 | |
| 34 gsmefr-decode This utility reads our gsmx format (which must be EFR, not FR1) | |
| 35 and feeds all frames and BFIs to our EFR decoder. The decoded | |
| 36 output is written as WAV. | |
| 37 | |
| 38 WAV reading and writing functions used by the above utilities have been lifted | |
| 39 out of opencore-amrnb test code. |