FreeCalypso > hg > gsm-codec-lib
annotate doc/Binary-file-format @ 109:2361a7d8c1eb
libgsmfrp: randomize grid position params when muting speech,
following GSM 06.11 example solution in more detail
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Mon, 28 Nov 2022 04:15:20 +0000 |
parents | 820d88b97924 |
children | 598ee3ce238b |
rev | line source |
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10
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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1 We (Themyscira Wireless) define our own binary file format for testing of GSM |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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2 06.10 (FR) and EFR codec functions; this format of ours is an extension of |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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3 classic .gsm format from libgsm/toast. The original libgsm file format is a |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
4 directly abutted sequence of 33-byte libgsm frames, equivalent to RTP frames |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
5 for GSM FR, with the upper nibble of the first byte in each frame equal to 0xD, |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
6 serving as a signature. We simply extend this idea: our version is still a |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
7 directly abutted sequence of binary records, but each record is now one of 3 |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
8 possibilities: |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
9 |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
10 - a 33-byte GSM FR frame in libgsm/RTP format, 0xD signature |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
11 - a 31-byte GSM EFR frame in RTP format (ETSI TS 101 318), 0xC signature |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
12 - a 2-byte Themyscira-extension BFI marker, 0xBF signature |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
13 |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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14 File reading functions begin by reading only one byte; this byte, once decoded, |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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15 tells us how many more bytes need to be read, and frame synchronization is thus |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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16 maintained. |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
17 |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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18 FR and EFR frames are not expected to be mixed in the same stream recording; |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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19 our low-level binary file reading function will grok such mixing just fine, but |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
20 each higher-level test program is expected to be written for only one codec, |
820d88b97924
libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
21 either FR or EFR. |