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TW-TS-005 reader: fix maximum line length bug TW-TS-005 section 4.1 states: The maximum allowed length of each line is 80 characters, not including the OS-specific newline encoding. The implementation of this line length limit in the TW-TS-005 hex file reader function in the present suite was wrong, such that lines of the full maximum length could not be read. Fix it. Note that this bug affects comment lines too, not just actual RTP payloads. Neither Annex A nor Annex B features an RTP payload format that goes to the maximum of 40 bytes, but if a comment line goes to the maximum allowed length of 80 characters not including the terminating newline, the bug will be triggered, necessitating the present fix.
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 25 Feb 2025 07:49:28 +0000
parents f469bad44c0e
children
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1 We (Themyscira Wireless) define our own binary file format for testing of GSM
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2 06.10 (FR) and EFR codec functions; this format of ours is an extension of
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3 classic .gsm format from libgsm/toast. The original libgsm file format is a
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4 directly abutted sequence of 33-byte libgsm frames, equivalent to RTP frames
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5 for GSM FR, with the upper nibble of the first byte in each frame equal to 0xD,
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6 serving as a signature. We simply extend this idea: our version is still a
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7 directly abutted sequence of binary records, but each record is now one of 3
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8 possibilities:
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10 - a 33-byte GSM FR frame in libgsm/RTP format, 0xD signature
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11 - a 31-byte GSM EFR frame in RTP format (ETSI TS 101 318), 0xC signature
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12 - a 2-byte Themyscira-extension BFI marker, 0xBF signature, see below
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14 File reading functions begin by reading only one byte; this byte, once decoded,
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15 tells us how many more bytes need to be read, and frame synchronization is thus
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16 maintained.
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18 The recommended filename suffix for extended-libgsm binary files in the present
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19 format is .gsmx; of course dot-separated filename suffixes hold absolutely no
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20 special meaning on Unix systems, but many developers still strongly prefer to
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21 have them for psychological comfort.
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23 Any gsmx file (FR or EFR) can be dumped in human-readable form with our
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24 gsmrec-dump utility. This utility turns every read frame from bytes into codec
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25 parameters with gsmfr_unpack_to_array() or EFR_frame2params(), and then displays
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26 those parameters in a sensible manner, with a per-frame header line followed by
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27 4 lines of subframe parameters.
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29 FR and EFR frames are not expected to be mixed in the same stream recording;
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30 our low-level binary file reading function and gsmrec-dump will grok such mixing
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31 just fine, but each higher-level test program (beyond gsmrec-dump) is expected
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32 to be written for only one codec, either FR or EFR.
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34 BFI marker format
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35 =================
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37 Every 20 ms frame in our gsmx files is either a good FR/EFR frame or a BFI (Bad
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38 Frame Indication) marker. The BFI marker format used in our gsmx file format is
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39 the same format which we (Themyscira Wireless) previously used in our GSM RAN
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40 RTP transport, before switching to our current TRAUlike RTP format. This BFI
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41 marker format is quite simple:
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43 byte 0: 0xBF signature;
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44 byte 1: least-significant bit encoding TAF per GSM 06.31 or GSM 06.81,
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45 section 6.1.1 in both documents; other bits are reserved.