[S] Change in osmo-bts[master]: csd_v110: set E2 bit correctly for TCH/[FH]4.8 NT

laforge has submitted this change. ( https://gerrit.osmocom.org/c/osmo-bts/+/38554?usp=email ) ( 3 is the latest approved patch-set. No files were changed between the latest approved patch-set and the submitted one. )Change subject: csd_v110: set E2 bit correctly for TCH/[FH]4.8 NT ...................................................................... csd_v110: set E2 bit correctly for TCH/[FH]4.8 NT In all classic NT modes below 14.5 kbit/s, V.110 frame bits E2 and E3 are repurposed to indicate the alignment whereby a single 240-bit RLP frame is composed of 4 pseudo-V.110 frames in switching transport. (TS 48.020 section 15.1.) In the case of TCH/F9.6, setting both E2 and E3 is easy because all 4 pseudo-V.110 frames go out in the same clearmode RTP packet as a result of a single channel decoding operation. However, in the case of TCH/F4.8 there are two separate channel decoding operations producing two separate RTP packets 20 ms apart. Furthermore, GSM 05.03 section 3.4.1 specifies which TDMA frame positions hold which half of the RLP frame - therefore, the correct emission of bit E2 needs to be based on the TDMA frame number at which the block was received. A similar situation occurs with TCH/H4.8 NT: we receive a single block from the 05.03 decoder every 40 ms, containing a full RLP frame, but we emit it as two separate RTP packets, each carrying 20 ms worth of bits. These RTP packets also require correct setting of E2 bit. Related: OS#6579 Change-Id: I485af5e01ea87c1721a298a486cd344a17884200 --- M include/osmo-bts/csd_v110.h M src/common/csd_v110.c M src/common/l1sap.c M tests/csd/csd_test.c 4 files changed, 30 insertions(+), 10 deletions(-) Approvals: Jenkins Builder: Verified fixeria: Looks good to me, approved pespin: Looks good to me, but someone else must approve diff --git a/include/osmo-bts/csd_v110.h b/include/osmo-bts/csd_v110.h index de868ae..a7c3a1b 100644 --- a/include/osmo-bts/csd_v110.h +++ b/include/osmo-bts/csd_v110.h @@ -14,6 +14,7 @@ extern const struct csd_v110_lchan_desc csd_v110_lchan_desc[256]; int csd_v110_rtp_encode(const struct gsm_lchan *lchan, uint8_t *rtp, - const uint8_t *data, size_t data_len); + const uint8_t *data, size_t data_len, + uint8_t nt48_half_num); int csd_v110_rtp_decode(const struct gsm_lchan *lchan, uint8_t *data, const uint8_t *rtp, size_t rtp_len); diff --git a/src/common/csd_v110.c b/src/common/csd_v110.c index 7254d2d..cbbb83b 100644 --- a/src/common/csd_v110.c +++ b/src/common/csd_v110.c @@ -78,7 +78,8 @@ }; int csd_v110_rtp_encode(const struct gsm_lchan *lchan, uint8_t *rtp, - const uint8_t *data, size_t data_len) + const uint8_t *data, size_t data_len, + uint8_t nt48_half_num) { const struct csd_v110_lchan_desc *desc; ubit_t ra_bits[80 * 4]; @@ -110,9 +111,15 @@ /* E1 .. E3 must set by out-of-band knowledge */ if (lchan->csd_mode == LCHAN_CSD_M_NT) { /* non-transparent: as per 3GPP TS 48.020, Table 7 */ - df.e_bits[0] = 0; /* E1: as per 15.1.2, shall be set to 0 (for BSS-MSC) */ - df.e_bits[1] = (i >> 1) & 0x01; /* E2: 0 for Q1/Q2, 1 for Q3/Q4 */ - df.e_bits[2] = (i >> 0) & 0x01; /* E3: 0 for Q1/Q3, 1 for Q2/Q4 */ + /* E1: as per 15.1.2, shall be set to 0 (for BSS-MSC) */ + df.e_bits[0] = 0; + /* E2: 0 for Q1/Q2, 1 for Q3/Q4 */ + if (desc->num_blocks == 4) + df.e_bits[1] = (i >> 1) & 0x01; + else + df.e_bits[1] = nt48_half_num; + /* E3: 0 for Q1/Q3, 1 for Q2/Q4 */ + df.e_bits[2] = (i >> 0) & 0x01; } else { /* transparent: as per 3GPP TS 44.021, Figure 4 */ df.e_bits[0] = e1e2e3_map[lchan->csd_mode][0]; /* E1 */ diff --git a/src/common/l1sap.c b/src/common/l1sap.c index 749598e..65ebf35 100644 --- a/src/common/l1sap.c +++ b/src/common/l1sap.c @@ -2056,15 +2056,27 @@ lchan->rtp_tx_marker = false; } +/* In the case of TCH/F4.8 NT, we have to set bit E2 based on the TDMA + * frame number at which we received the block in question. See + * GSM 05.03 section 3.4.1 and the mapping tables of GSM 05.02. */ +static const uint8_t tchf48_nt_e2_map[26] = { + [4] = 1, /* B1 position */ + [13] = 1, /* B3 position */ + [21] = 1, /* B5 position */ +}; + static void handle_tch_ind_csd_fr(struct gsm_lchan *lchan, const struct ph_tch_param *tch_ind, const uint8_t *data, uint16_t data_len) { uint8_t rtp_pl[RFC4040_RTP_PLEN]; + uint8_t tchf48_half = tchf48_nt_e2_map[tch_ind->fn % 26]; int rc; gsmtap_csd_rlp_process(lchan, true, tch_ind, data, data_len); - rc = csd_v110_rtp_encode(lchan, rtp_pl, data, data_len); + /* the last argument matters only for TCH/F4.8 NT mode, + * ignored in all other cases. */ + rc = csd_v110_rtp_encode(lchan, rtp_pl, data, data_len, tchf48_half); if (rc < 0) return; @@ -2076,7 +2088,7 @@ uint8_t rtp_pl[RFC4040_RTP_PLEN]; int rc, i; - rc = csd_v110_rtp_encode(lchan, rtp_pl, NULL, 0); + rc = csd_v110_rtp_encode(lchan, rtp_pl, NULL, 0, 0); if (rc < 0) return; @@ -2105,7 +2117,7 @@ for (i = 0; i < 2; i++) { rc = csd_v110_rtp_encode(lchan, rtp_pl, data + i * bits_per_20ms, - bits_per_20ms); + bits_per_20ms, i); if (rc < 0) return; send_ul_rtp_packet_hrdata(lchan, rtp_pl, sizeof(rtp_pl)); diff --git a/tests/csd/csd_test.c b/tests/csd/csd_test.c index b6edec9..15ee84f 100644 --- a/tests/csd/csd_test.c +++ b/tests/csd/csd_test.c @@ -124,7 +124,7 @@ data_enc[i] = i & 0x01; /* encode an RTP frame and print it */ - rc = csd_v110_rtp_encode(&lchan, &rtp[0], &data_enc[0], bit_num); + rc = csd_v110_rtp_encode(&lchan, &rtp[0], &data_enc[0], bit_num, 0); fprintf(stderr, "[i] csd_v110_rtp_encode() returns %d\n", rc); if (rc != RFC4040_RTP_PLEN) return; @@ -148,7 +148,7 @@ fprintf(stderr, "[i] Testing '%s' (IDLE)\n", tc->name); /* encode an idle RTP frame and print it */ - rc = csd_v110_rtp_encode(&lchan, &rtp[0], &data_enc[0], 0); + rc = csd_v110_rtp_encode(&lchan, &rtp[0], &data_enc[0], 0, 0); fprintf(stderr, "[i] csd_v110_rtp_encode() returns %d\n", rc); if (rc != RFC4040_RTP_PLEN) return; -- To view, visit https://gerrit.osmocom.org/c/osmo-bts/+/38554?usp=email To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings?usp=email Gerrit-MessageType: merged Gerrit-Project: osmo-bts Gerrit-Branch: master Gerrit-Change-Id: I485af5e01ea87c1721a298a486cd344a17884200 Gerrit-Change-Number: 38554 Gerrit-PatchSet: 4 Gerrit-Owner: falconia &lt;falcon(a)freecalypso.org&gt; Gerrit-Reviewer: Jenkins Builder Gerrit-Reviewer: fixeria &lt;vyanitskiy(a)sysmocom.de&gt; Gerrit-Reviewer: laforge &lt;laforge(a)osmocom.org&gt; Gerrit-Reviewer: pespin &lt;pespin(a)sysmocom.de&gt;