/* * (C) 2012 by Pablo Neira Ayuso * (C) 2012 by On Waves ehf * * SPDX-License-Identifier: GPL-2.0+ * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. */ #include #include #include #include #include #include /* According to TS 26.101 Table A.1b: * * Frame type AMR code bits bytes * 0 4.75 95 12 * 1 5.15 103 13 * 2 5.90 118 15 * 3 6.70 134 17 * 4 7.40 148 19 * 5 7.95 159 20 * 6 10.20 204 26 * 7 12.20 244 31 * 8 AMR SID 39 5 * 9 GSM-EFR SID 43 5 * 10 TDMA-EFR SID 38 5 * 11 PDC-EFR SID 37 5 * 12 NOT USED * 13 NOT USED * 14 NOT USED * 15 NO DATA 0 0 */ static int amr_ft_to_bits[AMR_FT_MAX] = { [AMR_FT_0] = AMR_FT_0_LEN_BITS, [AMR_FT_1] = AMR_FT_1_LEN_BITS, [AMR_FT_2] = AMR_FT_2_LEN_BITS, [AMR_FT_3] = AMR_FT_3_LEN_BITS, [AMR_FT_4] = AMR_FT_4_LEN_BITS, [AMR_FT_5] = AMR_FT_5_LEN_BITS, [AMR_FT_6] = AMR_FT_6_LEN_BITS, [AMR_FT_7] = AMR_FT_7_LEN_BITS, [AMR_FT_SID] = AMR_FT_SID_LEN_BITS, [AMR_FT_GSM_EFR_SID] = AMR_FT_GSM_EFR_SID_LEN_BITS, [AMR_FT_TDMA_EFR_SID] = AMR_FT_TDMA_EFR_SID_LEN_BITS, [AMR_FT_PDC_EFR_SID] = AMR_FT_PDC_EFR_SID_LEN_BITS, [12] = 0, /* for future use */ [13] = 0, /* for future use */ [14] = 0, /* for future use */ [AMR_FT_NO_DATA] = AMR_FT_NO_DATA_LEN_BITS, }; static size_t amr_ft_to_bytes[AMR_FT_MAX] = { [AMR_FT_0] = AMR_FT_0_LEN, [AMR_FT_1] = AMR_FT_1_LEN, [AMR_FT_2] = AMR_FT_2_LEN, [AMR_FT_3] = AMR_FT_3_LEN, [AMR_FT_4] = AMR_FT_4_LEN, [AMR_FT_5] = AMR_FT_5_LEN, [AMR_FT_6] = AMR_FT_6_LEN, [AMR_FT_7] = AMR_FT_7_LEN, [AMR_FT_SID] = AMR_FT_SID_LEN, [AMR_FT_GSM_EFR_SID] = AMR_FT_GSM_EFR_SID_LEN, [AMR_FT_TDMA_EFR_SID] = AMR_FT_TDMA_EFR_SID_LEN, [AMR_FT_PDC_EFR_SID] = AMR_FT_PDC_EFR_SID_LEN, [12] = 0, /* for future use */ [13] = 0, /* for future use */ [14] = 0, /* for future use */ [AMR_FT_NO_DATA] = AMR_FT_NO_DATA_LEN, }; size_t osmo_amr_bits(uint8_t amr_ft) { OSMO_ASSERT(amr_ft < AMR_FT_MAX); return amr_ft_to_bits[amr_ft]; } size_t osmo_amr_bytes(uint8_t amr_ft) { OSMO_ASSERT(amr_ft < AMR_FT_MAX); return amr_ft_to_bytes[amr_ft]; } int osmo_amr_bytes_to_ft(size_t bytes) { int ft; for (ft = 0; ft < AMR_FT_PDC_EFR_SID; ft++) { if (amr_ft_to_bytes[ft] == bytes) return ft; } /* 12-14 not used, jump to 15 (AMR_FT_NO_DATA): */ if (amr_ft_to_bytes[AMR_FT_NO_DATA] == bytes) return AMR_FT_NO_DATA; return -1; } int osmo_amr_ft_valid(uint8_t amr_ft) { return amr_ft <= AMR_FT_PDC_EFR_SID || amr_ft == AMR_FT_NO_DATA; } /*! Check if an AMR frame is octet aligned by looking at the padding bits. * \param[inout] payload user provided memory containing the AMR payload. * \param[in] payload_len overall length of the AMR payload. * \returns true when the payload is octet aligned. */ bool osmo_amr_is_oa(const uint8_t *payload, unsigned int payload_len) { /* NOTE: The distinction between octet-aligned and bandwith-efficient * mode normally relys on out of band methods that explicitly select * one of the two modes. (See also RFC 3267, chapter 3.8). However the * A interface in GSM does not provide ways to communicate which mode * is exactly used. The following functions uses some heuristics to * check if an AMR payload is octet aligned or not. */ struct amr_hdr *oa_hdr = (struct amr_hdr *)payload; unsigned int frame_len; /* Broken payload? */ if (!payload || payload_len < sizeof(struct amr_hdr)) return false; /* In octet aligned mode, padding bits are specified to be * set to zero. (However, there is a remaining risk that the FT0 or FT1 * is selected and the first two bits of the frame are zero as well, * in this case a bandwith-efficient mode payload would look like an * octet-aligned payload, thats why additional checks are required.) */ if (oa_hdr->pad1 != 0) return false; if (oa_hdr->pad2 != 0) return false; /* This implementation is limited to single-frame payloads only and * since multi-frame payloads are not common in GSM anyway, we may * include the final bit of the first header into this check. */ if (oa_hdr->f != 0) return false; /* Match the length of the received payload against the expected frame * length that is defined by the frame type. */ if (!osmo_amr_ft_valid(oa_hdr->ft)) return false; frame_len = osmo_amr_bytes(oa_hdr->ft); if (frame_len != payload_len - sizeof(struct amr_hdr)) return false; return true; } /*! Convert an AMR frame from octet-aligned mode to bandwith-efficient mode. * \param[inout] payload user provided memory containing the AMR payload. * \param[in] payload_len overall length of the AMR payload. * \returns resulting payload length, -1 on error. */ int osmo_amr_oa_to_bwe(uint8_t *payload, unsigned int payload_len) { struct amr_hdr *oa_hdr = (struct amr_hdr *)payload; unsigned int ft = oa_hdr->ft; unsigned int frame_len = payload_len - sizeof(struct amr_hdr); unsigned int i; int bwe_payload_len; /* This implementation is not capable to handle multi-frame * packets, so we need to make sure that the frame we operate on * contains only one payload. */ if (oa_hdr->f != 0) return -1; /* Check for valid FT (AMR mode) value */ if (!osmo_amr_ft_valid(oa_hdr->ft)) return -1; /* Move TOC close to CMR */ payload[0] = (payload[0] & 0xf0) | ((payload[1] >> 4) & 0x0f); payload[1] = (payload[1] << 4) & 0xf0; for (i = 0; i < frame_len; i++) { payload[i + 1] |= payload[i + 2] >> 2; payload[i + 2] = payload[i + 2] << 6; } /* Calculate new payload length */ bwe_payload_len = OSMO_BYTES_FOR_BITS(AMR_HDR_BWE_LEN_BITS + osmo_amr_bits(ft)); return bwe_payload_len; } /*! Convert an AMR frame from bandwith-efficient mode to octet-aligned mode. * \param[inout] payload user provided memory containing the AMR payload. * \param[in] payload_len overall length of the AMR payload. * \param[in] payload_maxlen maximum length of the user provided memory. * \returns resulting payload length, -1 on error. */ int osmo_amr_bwe_to_oa(uint8_t *payload, unsigned int payload_len, unsigned int payload_maxlen) { uint8_t buf[256]; /* The header is only valid after shifting first two bytes to OA mode */ struct amr_hdr_bwe *bwe_hdr = (struct amr_hdr_bwe *)payload; struct amr_hdr *oa_hdr; unsigned int i; unsigned int oa_payload_len; uint8_t ft; if (payload_len < sizeof(struct amr_hdr_bwe)) return -1; if (payload_len + 1 > payload_maxlen) return -1; if (payload_len + 1 > sizeof(buf)) return -1; ft = (bwe_hdr->ft_hi << 1) | bwe_hdr->ft_lo; if (!osmo_amr_ft_valid(ft)) return -1; if (OSMO_BYTES_FOR_BITS(AMR_HDR_BWE_LEN_BITS + osmo_amr_bits(ft)) > payload_len) return -1; memset(buf, 0, sizeof(buf)); oa_hdr = (struct amr_hdr *)buf; oa_hdr->cmr = bwe_hdr->cmr; oa_hdr->f = bwe_hdr->f; oa_hdr->ft = ft; oa_hdr->q = bwe_hdr->q; /* Calculate new payload length */ oa_payload_len = 2 + osmo_amr_bytes(ft); for (i = 2; i < oa_payload_len - 1; i++) { buf[i] = payload[i - 1] << 2; buf[i] |= payload[i] >> 6; } buf[i] = payload[i - 1] << 2; memcpy(payload, buf, oa_payload_len); return oa_payload_len; } /*! Convert an AMR frame from bandwith-efficient mode to IuuP/IuFP payload. * The IuuP/IuPF payload only contains the class a, b, c bits. No header. * \param[inout] payload user provided memory containing the AMR payload. * \param[in] payload_len overall length of the AMR payload. * \param[in] payload_maxlen maximum length of the user provided memory. * \returns resulting payload length, negative on error. */ int osmo_amr_bwe_to_iuup(uint8_t *payload, unsigned int payload_len) { /* The header is only valid after shifting first two bytes to OA mode */ unsigned int i, required_len_bits; unsigned int amr_speech_len_bytes, amr_speech_len_bits; uint8_t ft; if (payload_len < 2) return -1; /* Calculate new payload length */ ft = ((payload[0] & 0x07) << 1) | ((payload[1] & 0x80) >> 7); if (!osmo_amr_ft_valid(ft)) return -1; amr_speech_len_bits = osmo_amr_bits(ft); amr_speech_len_bytes = osmo_amr_bytes(ft); /* shift of AMR_HDR_BWE_LEN_BITS (10) bits, aka remove BWE Hdr + ToC: */ required_len_bits = AMR_HDR_BWE_LEN_BITS + amr_speech_len_bits; if (payload_len < OSMO_BYTES_FOR_BITS(required_len_bits)) return -1; for (i = 0; i < amr_speech_len_bytes; i++) { /* we have to shift the payload by 10 bits to get only the Class A, B, C bits */ payload[i] = (payload[i + 1] << 2) | ((payload[i + 2]) >> 6); } return amr_speech_len_bytes; } /*! Convert an AMR frame from IuuP/IuFP payload to bandwith-efficient mode. * The IuuP/IuPF payload only contains the class a, b, c bits. No header. * The resulting buffer has space at the start prepared to be filled by CMR, TOC. * \param[inout] payload user provided memory containing the AMR payload. * \param[in] payload_len overall length of the AMR payload. * \param[in] payload_maxlen maximum length of the user provided memory (payload_len + 2 required). * \returns resulting payload length, negative on error. */ int osmo_amr_iuup_to_bwe(uint8_t *payload, unsigned int payload_len, unsigned int payload_maxlen) { /* shift all bits by AMR_HDR_BWE_LEN_BITS (10) */ unsigned int i, required_len_bits, required_len_bytes; int ft = osmo_amr_bytes_to_ft(payload_len); if (ft < 0) return ft; required_len_bits = osmo_amr_bits(ft) + 10; required_len_bytes = OSMO_BYTES_FOR_BITS(required_len_bits); if (payload_maxlen < required_len_bytes) return -1; i = payload_len + 1; payload[i] = (payload[i - 2] << 6); for (i = payload_len; i >= 2; i--) { /* we have to shift the payload by AMR_HDR_BWE_LEN_BITS (10) bits to prepend BWE Hdr + ToC */ payload[i] = (payload[i - 1] >> 2) | (payload[i - 2] << 6); } payload[i] = (payload[i - 1] >> 2); payload[0] = 0; return required_len_bytes; }