laforge has submitted this change. ( https://gerrit.osmocom.org/c/libosmocore/+/35131?usp=email ) Change subject: coding: gsm0503_tch_{afs,ahs}_encode(): add ability to emit BFI ...................................................................... coding: gsm0503_tch_{afs,ahs}_encode(): add ability to emit BFI Similar to Change ID Iade3310e16b906efb6892d28f474a0d15204e861, add BFI support to TCH AFS and TCH AHS encoder. Every BTS needs to have some graceful handling for the scenario where it is time to send out a speech frame on TCH DL, but there is no frame to be sent. One possible solution is to transmit dummy FACCH, but this option is unattractive for TCH/AHS where FACCH displaces two speech frames rather than one. A more elegant solution is to emit a speech frame with inverted CRC6, causing the MS receiver to declare a BFI condition to trigger substitution and muting procedure. Setting all u(k) bits to 0 is one way to produce such an inverted-CRC speech frame (normal TCH FR/HR CRC6 for an all-zeros frame would be 111111). This patch adds the abiliy to gsm0503_tch_{afs,ahs}_encode() functions, indicated by payload length of 0. See §6.2 of 3GPP TS 26.191 for substitution and muting procedure. Related: OS#6049 Change-Id: I82ce2adf995a4b42d1f378c5819f88d773b9104a --- M src/coding/gsm0503_coding.c 1 file changed, 171 insertions(+), 58 deletions(-) Approvals: laforge: Looks good to me, approved fixeria: Looks good to me, but someone else must approve Jenkins Builder: Verified diff --git a/src/coding/gsm0503_coding.c b/src/coding/gsm0503_coding.c index 8effef5..365ae6e 100644 --- a/src/coding/gsm0503_coding.c +++ b/src/coding/gsm0503_coding.c @@ -2439,7 +2439,7 @@ /*! Perform channel encoding on a TCH/AFS channel according to TS 05.03 * \param[out] bursts caller-allocated output buffer for bursts bits * \param[in] tch_data Codec input data in RTP payload format - * \param[in] len Length of \a tch_data in bytes + * \param[in] len Length of \a tch_data in bytes or 0 to generate a bad frame * \param[in] codec_mode_req Use CMR (1) or FT (0) * \param[in] codec Array of codecs (active codec set) * \param[in] codecs Number of entries in \a codec @@ -2473,12 +2473,19 @@ switch (codec[ft]) { case 7: /* TCH/AFS12.2 */ - if (len != 31) - goto invalid_length; + if (!len) { + /* No data, induce BFI in the receiver by inverted CRC bits. + * The data bit are all 0, so the correct parity bits would be 111111. */ + memset(d, 0, 244); + memset(p, 0, 6); + } else { + if (len != 31) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 244); + tch_amr_disassemble(d, tch_data, 244); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 81, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 81, p); + } tch_amr_merge(conv, d, p, 244, 81); @@ -2486,12 +2493,18 @@ break; case 6: /* TCH/AFS10.2 */ - if (len != 26) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 204); + memset(p, 0, 6); + } else { + if (len != 26) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 204); + tch_amr_disassemble(d, tch_data, 204); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 65, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 65, p); + } tch_amr_merge(conv, d, p, 204, 65); @@ -2499,12 +2512,18 @@ break; case 5: /* TCH/AFS7.95 */ - if (len != 20) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 159); + memset(p, 0, 6); + } else { + if (len != 20) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 159); + tch_amr_disassemble(d, tch_data, 159); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 75, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 75, p); + } tch_amr_merge(conv, d, p, 159, 75); @@ -2512,12 +2531,18 @@ break; case 4: /* TCH/AFS7.4 */ - if (len != 19) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 148); + memset(p, 0, 6); + } else { + if (len != 19) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 148); + tch_amr_disassemble(d, tch_data, 148); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 61, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 61, p); + } tch_amr_merge(conv, d, p, 148, 61); @@ -2525,12 +2550,18 @@ break; case 3: /* TCH/AFS6.7 */ - if (len != 17) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 134); + memset(p, 0, 6); + } else { + if (len != 17) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 134); + tch_amr_disassemble(d, tch_data, 134); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); + } tch_amr_merge(conv, d, p, 134, 55); @@ -2538,12 +2569,18 @@ break; case 2: /* TCH/AFS5.9 */ - if (len != 15) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 118); + memset(p, 0, 6); + } else { + if (len != 15) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 118); + tch_amr_disassemble(d, tch_data, 118); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); + } tch_amr_merge(conv, d, p, 118, 55); @@ -2551,12 +2588,18 @@ break; case 1: /* TCH/AFS5.15 */ - if (len != 13) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 103); + memset(p, 0, 6); + } else { + if (len != 13) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 103); + tch_amr_disassemble(d, tch_data, 103); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 49, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 49, p); + } tch_amr_merge(conv, d, p, 103, 49); @@ -2564,12 +2607,18 @@ break; case 0: /* TCH/AFS4.75 */ - if (len != 12) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 95); + memset(p, 0, 6); + } else { + if (len != 12) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 95); + tch_amr_disassemble(d, tch_data, 95); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 39, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 39, p); + } tch_amr_merge(conv, d, p, 95, 39); @@ -2927,7 +2976,7 @@ /*! Perform channel encoding on a TCH/AHS channel according to TS 05.03 * \param[out] bursts caller-allocated output buffer for bursts bits * \param[in] tch_data Codec input data in RTP payload format - * \param[in] len Length of \a tch_data in bytes + * \param[in] len Length of \a tch_data in bytes or 0 to generate a bad frame * \param[in] codec_mode_req Use CMR (1) or FT (0) * \param[in] codec Array of codecs (active codec set) * \param[in] codecs Number of entries in \a codec @@ -2970,12 +3019,19 @@ switch (codec[ft]) { case 5: /* TCH/AHS7.95 */ - if (len != 20) - goto invalid_length; + if (!len) { + /* No data, induce BFI in the receiver by inverted CRC bits. + * The data bit are all 0, so the correct parity bits would be 111111. */ + memset(d, 0, 159); + memset(p, 0, 6); + } else { + if (len != 20) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 159); + tch_amr_disassemble(d, tch_data, 159); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 67, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 67, p); + } tch_amr_merge(conv, d, p, 123, 67); @@ -2985,12 +3041,18 @@ break; case 4: /* TCH/AHS7.4 */ - if (len != 19) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 148); + memset(p, 0, 6); + } else { + if (len != 19) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 148); + tch_amr_disassemble(d, tch_data, 148); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 61, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 61, p); + } tch_amr_merge(conv, d, p, 120, 61); @@ -3000,12 +3062,18 @@ break; case 3: /* TCH/AHS6.7 */ - if (len != 17) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 134); + memset(p, 0, 6); + } else { + if (len != 17) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 134); + tch_amr_disassemble(d, tch_data, 134); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); + } tch_amr_merge(conv, d, p, 110, 55); @@ -3015,12 +3083,18 @@ break; case 2: /* TCH/AHS5.9 */ - if (len != 15) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 118); + memset(p, 0, 6); + } else { + if (len != 15) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 118); + tch_amr_disassemble(d, tch_data, 118); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); + } tch_amr_merge(conv, d, p, 102, 55); @@ -3030,12 +3104,18 @@ break; case 1: /* TCH/AHS5.15 */ - if (len != 13) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 103); + memset(p, 0, 6); + } else { + if (len != 13) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 103); + tch_amr_disassemble(d, tch_data, 103); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 49, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 49, p); + } tch_amr_merge(conv, d, p, 91, 49); @@ -3045,12 +3125,18 @@ break; case 0: /* TCH/AHS4.75 */ - if (len != 12) - goto invalid_length; + if (!len) { + /* See comment above. */ + memset(d, 0, 95); + memset(p, 0, 6); + } else { + if (len != 12) + goto invalid_length; - tch_amr_disassemble(d, tch_data, 95); + tch_amr_disassemble(d, tch_data, 95); - osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 39, p); + osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 39, p); + } tch_amr_merge(conv, d, p, 83, 39); -- To view, visit https://gerrit.osmocom.org/c/libosmocore/+/35131?usp=email To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: libosmocore Gerrit-Branch: master Gerrit-Change-Id: I82ce2adf995a4b42d1f378c5819f88d773b9104a Gerrit-Change-Number: 35131 Gerrit-PatchSet: 3 Gerrit-Owner: jolly <andreas@eversberg.eu> Gerrit-Reviewer: Jenkins Builder Gerrit-Reviewer: falconia <falcon@freecalypso.org> Gerrit-Reviewer: fixeria <vyanitskiy@sysmocom.de> Gerrit-Reviewer: laforge <laforge@osmocom.org> Gerrit-MessageType: merged