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comparison doc/AMR-hex-utils @ 592:24aba0e7aa35
document AMR hex (TW-TS-005 Annex C) utilities addition
| author | Mychaela Falconia <falcon@freecalypso.org> |
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| date | Fri, 07 Nov 2025 00:41:56 +0000 |
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| 591:2f1e91dd552b | 592:24aba0e7aa35 |
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| 1 As Themyscira Wireless work extends further into AMR, we now have the option of | |
| 2 storing sequences of AMR RTP payloads in a TW-TS-005 hexadecimal file. (See | |
| 3 TW-TS-005 article.) TW-TS-005 was originally intended for FR/EFR and HRv1 | |
| 4 codecs, but beginning with spec version 1.1.0, newly added Annex C specifies | |
| 5 how TW-TS-005 hex format may be used for AMR. As explained in that annex, any | |
| 6 workflow involving TW-TS-005 Annex C hex files requires out-of-band knowledge | |
| 7 as to which RTP payload format is captured: bandwidth-efficient (BWE) or | |
| 8 octet-aligned (OA). | |
| 9 | |
| 10 The following format conversion utilities are provided for working with | |
| 11 TW-TS-005 Annex C hex files: | |
| 12 | |
| 13 amr-hex-bwe2oa Both input and output are hex files; input is BWE, output is OA. | |
| 14 | |
| 15 amr-hex-oa2bwe Both input and output are hex files; input is OA, output is BWE. | |
| 16 | |
| 17 amr-hexoa2ietf Input is a hex file in OA format, output is RFC 4867 storage | |
| 18 format (binary *.amr). | |
| 19 | |
| 20 amr-ietf2hexoa Input is RFC 4867 storage format (binary *.amr), output is | |
| 21 TW-TS-005 hex with RTP payloads in OA format. | |
| 22 | |
| 23 Input to amr-hex-oa2bwe and amr-hexoa2ietf conversion utilities may be either | |
| 24 standard RFC 4867 OA or TW-TS-006 OAX (OA extended) - however, extended | |
| 25 information content in OAX format cannot be converted to BWE or RFC 4867 storage | |
| 26 format, hence any such extended info will be lost. However, in the absence of | |
| 27 OAX, using only standard RTP payload formats per RFC 4867, conversion between | |
| 28 BWE and OA is lossless. | |
| 29 | |
| 30 Conversion from TW-TS-005 Annex C to RFC 4867 storage format is lossy: CMR field | |
| 31 exists in RTP and thus in TW-TS-005 hex recordings, but not in RFC 4867 storage | |
| 32 format. amr-ietf2hexoa conversion utility sets CMR to 15 (NO_DATA); if some | |
| 33 other CMR is desired, the desired effect can be trivially achieved by applying | |
| 34 sed to amr-ietf2hexoa output. |