FreeCalypso > hg > gsm-codec-lib

annotate doc/Binary-file-format @ 282:9ee8ad3d4d30

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
frtest: rm gsmfr-hand-test and gsmfr-max-out utils These hack programs were never properly documented and were written only as part of a debug chase, in pursuit of a bug that ultimately turned out to be in our then-hacky patch to osmo-bts-sysmo, before beginning of proper patches in Osmocom. These hack programs need to be dropped from the present sw package because they depend on old libgsm, and we are eliminating that dependency.
author Mychaela Falconia <falcon@freecalypso.org>
date Sun, 14 Apr 2024 05:44:47 +0000
parents 7e490a8efe8a
children f469bad44c0e
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
10
820d88b97924 libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
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
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
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
210
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
12 - a 2-byte Themyscira-extension BFI marker, 0xBF signature, see below
10
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
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
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
16 maintained.
820d88b97924 libtest: implement binary file reader
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
17
124
598ee3ce238b doc/Binary-file-format: document .gsmx suffix
Mychaela Falconia <falcon@freecalypso.org>
parents: 10
diff changeset
18 The recommended filename suffix for extended-libgsm binary files in the present
598ee3ce238b doc/Binary-file-format: document .gsmx suffix
Mychaela Falconia <falcon@freecalypso.org>
parents: 10
diff changeset
19 format is .gsmx; of course dot-separated filename suffixes hold absolutely no
598ee3ce238b doc/Binary-file-format: document .gsmx suffix
Mychaela Falconia <falcon@freecalypso.org>
parents: 10
diff changeset
20 special meaning on Unix systems, but many developers still strongly prefer to
598ee3ce238b doc/Binary-file-format: document .gsmx suffix
Mychaela Falconia <falcon@freecalypso.org>
parents: 10
diff changeset
21 have them for psychological comfort.
133
b4b1c3a192c7 doc/Binary-file-format: document gsmrec-dump
Mychaela Falconia <falcon@freecalypso.org>
parents: 124
diff changeset
22
b4b1c3a192c7 doc/Binary-file-format: document gsmrec-dump
Mychaela Falconia <falcon@freecalypso.org>
parents: 124
diff changeset
23 Any gsmx file (FR or EFR) can be dumped in human-readable form with our
b4b1c3a192c7 doc/Binary-file-format: document gsmrec-dump
Mychaela Falconia <falcon@freecalypso.org>
parents: 124
diff changeset
24 gsmrec-dump utility. This utility turns every read frame from bytes into codec
b4b1c3a192c7 doc/Binary-file-format: document gsmrec-dump
Mychaela Falconia <falcon@freecalypso.org>
parents: 124
diff changeset
25 parameters with gsm_explode() or EFR_frame2params(), and then displays those
b4b1c3a192c7 doc/Binary-file-format: document gsmrec-dump
Mychaela Falconia <falcon@freecalypso.org>
parents: 124
diff changeset
26 parameters in a sensible manner, with a per-frame header line followed by 4
b4b1c3a192c7 doc/Binary-file-format: document gsmrec-dump
Mychaela Falconia <falcon@freecalypso.org>
parents: 124
diff changeset
27 lines of subframe parameters.
b4b1c3a192c7 doc/Binary-file-format: document gsmrec-dump
Mychaela Falconia <falcon@freecalypso.org>
parents: 124
diff changeset
28
b4b1c3a192c7 doc/Binary-file-format: document gsmrec-dump
Mychaela Falconia <falcon@freecalypso.org>
parents: 124
diff changeset
29 FR and EFR frames are not expected to be mixed in the same stream recording;
b4b1c3a192c7 doc/Binary-file-format: document gsmrec-dump
Mychaela Falconia <falcon@freecalypso.org>
parents: 124
diff changeset
30 our low-level binary file reading function and gsmrec-dump will grok such mixing
b4b1c3a192c7 doc/Binary-file-format: document gsmrec-dump
Mychaela Falconia <falcon@freecalypso.org>
parents: 124
diff changeset
31 just fine, but each higher-level test program (beyond gsmrec-dump) is expected
b4b1c3a192c7 doc/Binary-file-format: document gsmrec-dump
Mychaela Falconia <falcon@freecalypso.org>
parents: 124
diff changeset
32 to be written for only one codec, either FR or EFR.
210
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
33
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
34 BFI marker format
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
35 =================
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
36
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
37 Every 20 ms frame in our gsmx files is either a good FR/EFR frame or a BFI (Bad
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
38 Frame Indication) marker. The BFI marker format used in our gsmx file format is
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
39 the same format which we (Themyscira Wireless) previously used in our GSM RAN
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
40 RTP transport, before switching to our current TRAUlike RTP format. This BFI
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
41 marker format is quite simple:
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
42
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
43 byte 0: 0xBF signature;
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
44 byte 1: least-significant bit encoding TAF per GSM 06.31 or GSM 06.81,
7e490a8efe8a doc/Binary-file-format: document BFI marker format
Mychaela Falconia <falcon@freecalypso.org>
parents: 133
diff changeset
45 section 6.1.1 in both documents; other bits are reserved.