falconia has uploaded this change for review. ( https://gerrit.osmocom.org/c/libosmo-abis/+/39495?usp=email )
Change subject: trau: implement TFO frame encoding function ......................................................................
trau: implement TFO frame encoding function
Most differences between regular TRAU frames of TS 48.060 & 48.061 and TFO frames of TS 28.062 matter only in the frame decoding direction. In the encoding direction, regular osmo_trau_frame_encode() would have been sufficient for both frame types if it weren't for the quirk of setting C1..C5 bits. osmo_trau_frame_encode() sets these bits per its own mind for most frame types, ignoring the bits passed by the user in fr->c_bits[]. This API behavior cannot be changed without breaking existing users, but it is bad for TFO.
Solution: implement new osmo_trau_frame_encode_tfo() function for TFO applications. As an additional benefit, the output buffer space requirement is reduced because there is no possibility of output frame extension for timing alignment.
Change-Id: I6e0ab4e5115f0aa6979ce93955b0e95b09041091 --- M include/osmocom/trau/trau_frame.h M src/trau/trau_frame.c 2 files changed, 120 insertions(+), 37 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/libosmo-abis refs/changes/95/39495/1
diff --git a/include/osmocom/trau/trau_frame.h b/include/osmocom/trau/trau_frame.h index 8bdeb73..dd14f27 100644 --- a/include/osmocom/trau/trau_frame.h +++ b/include/osmocom/trau/trau_frame.h @@ -151,6 +151,8 @@ /* TFO frames are slightly modified TRAU-UL frames, and thus require slightly * modified encoding and decoding functions. */
+int osmo_trau_frame_encode_tfo(ubit_t *bits, size_t n_bits, const struct osmo_trau_frame *fr); + int osmo_trau_frame_decode_tfo_16k(struct osmo_trau_frame *fr, const ubit_t *bits); int osmo_trau_frame_decode_tfo_hr1(struct osmo_trau_frame *fr, const ubit_t *bits); int osmo_trau_frame_decode_tfo_amr_8k(struct osmo_trau_frame *fr, const ubit_t *bits); diff --git a/src/trau/trau_frame.c b/src/trau/trau_frame.c index df4404d..fb98247 100644 --- a/src/trau/trau_frame.c +++ b/src/trau/trau_frame.c @@ -238,30 +238,34 @@ }
/* TS 08.60 Section 3.1.1 */ -static int encode16_fr(ubit_t *trau_bits, const struct osmo_trau_frame *fr) +static int encode16_fr(ubit_t *trau_bits, const struct osmo_trau_frame *fr, bool is_tfo) { const ubit_t *cbits5; int i; int d_idx = 0;
- switch (fr->type) { - case OSMO_TRAU16_FT_IDLE: - if (fr->dir == OSMO_TRAU_DIR_UL) - cbits5 = ft_idle_up_bits; - else - cbits5 = ft_idle_down_bits; - break; - case OSMO_TRAU16_FT_FR: - if (fr->dir == OSMO_TRAU_DIR_UL) - cbits5 = ft_fr_up_bits; - else - cbits5 = ft_fr_down_bits; - break; - case OSMO_TRAU16_FT_EFR: - cbits5 = ft_efr_bits; - break; - default: - return -EINVAL; + if (is_tfo) { + cbits5 = fr->c_bits; + } else { + switch (fr->type) { + case OSMO_TRAU16_FT_IDLE: + if (fr->dir == OSMO_TRAU_DIR_UL) + cbits5 = ft_idle_up_bits; + else + cbits5 = ft_idle_down_bits; + break; + case OSMO_TRAU16_FT_FR: + if (fr->dir == OSMO_TRAU_DIR_UL) + cbits5 = ft_fr_up_bits; + else + cbits5 = ft_fr_down_bits; + break; + case OSMO_TRAU16_FT_EFR: + cbits5 = ft_efr_bits; + break; + default: + return -EINVAL; + } }
encode_sync16(trau_bits); @@ -314,17 +318,21 @@ }
/* TS 08.60 Section 3.1.2 */ -static int encode16_amr(ubit_t *trau_bits, const struct osmo_trau_frame *fr) +static int encode16_amr(ubit_t *trau_bits, const struct osmo_trau_frame *fr, bool is_tfo) { - const ubit_t *cbits5 = ft_amr_bits; int i, d_idx;
encode_sync16(trau_bits);
- /* C1 .. C5 */ - memcpy(trau_bits + 17, cbits5 + 0, 5); - /* C6 .. C15 */ - memcpy(trau_bits + 17 + 5, fr->c_bits + 5, 15 - 5); + if (is_tfo) { + /* C1 .. C15 */ + memcpy(trau_bits + 17, fr->c_bits, 15); + } else { + /* C1 .. C5 */ + memcpy(trau_bits + 17, ft_amr_bits, 5); + /* C6 .. C15 */ + memcpy(trau_bits + 17 + 5, fr->c_bits + 5, 15 - 5); + }
trau_bits[32] = 1; /* C16 .. C25 */ @@ -549,7 +557,7 @@ fr_idle_frame.c_bits[11] = 1; /* C12 (UFE), good frame */ fr_idle_frame.c_bits[15] = 1; /* C16 (SP), no DTX */
- encode16_fr(encoded_idle_frame, &fr_idle_frame); + encode16_fr(encoded_idle_frame, &fr_idle_frame, false); dbits_initted = 1; /* set it to 1 to not call it again */ } return encoded_idle_frame; @@ -843,7 +851,7 @@ }
/* TS 08.61 Section 5.2.1.1 */ -static int encode8_hr(ubit_t *trau_bits, const struct osmo_trau_frame *fr) +static int encode8_hr(ubit_t *trau_bits, const struct osmo_trau_frame *fr, bool is_tfo) { int i, d_idx = 0;
@@ -858,11 +866,15 @@ /* C1 .. C5 */ ubit_t *cbits_out = trau_bits + 1 * 8 + 1; if (fr->dir == OSMO_TRAU_DIR_UL) { - cbits_out[0] = 0; - cbits_out[1] = 0; - cbits_out[2] = 0; - cbits_out[3] = 1; - cbits_out[4] = 0; + if (is_tfo) { + memcpy(cbits_out, fr->c_bits, 5); + } else { + cbits_out[0] = 0; + cbits_out[1] = 0; + cbits_out[2] = 0; + cbits_out[3] = 1; + cbits_out[4] = 0; + } } else { cbits_out[0] = 0; cbits_out[1] = 0; @@ -1241,9 +1253,21 @@
/*! Encode a TRAU frame from its decoded representation to a sequence of unpacked bits. * \param[out] bits caller-allocated buffer for unpacked outpud bits - * \param[in] n_bits size of 'bits' oputput buffer in number of unpacked bits + * \param[in] n_bits size of 'bits' output buffer in number of unpacked bits * \param[in] fr decoded representation of TRAU frame to be encoded - * \return 0 number of unpacked output bits generated; negative in case of error */ + * \return 0 number of unpacked output bits generated; negative in case of error + * + * This function exhibits a behavioral quirk which users need to be aware of: + * for many frame types, the first 5 bits out of user-provided fr->c_bits[] + * (corresponding to C1..C5) are ignored and replaced with internally supplied + * constant values, where the function "knows" what the correct frame type code + * should be. This behavioral quirk is arguably a design defect, but it cannot + * be changed without breaking some existing applications that rely on this + * behavior and skip setting those bits themselves. For TFO applications + * where C1..C5 may need to be modified (especially TFO-AMR where this C1..C5 + * modification must be done before CRC computation), please use + * osmo_trau_frame_encode_tfo(). + */ int osmo_trau_frame_encode(ubit_t *bits, size_t n_bits, const struct osmo_trau_frame *fr) { /* check for sufficient space provided by caller in output buffer */ @@ -1287,11 +1311,11 @@ switch (fr->type) { case OSMO_TRAU16_FT_FR: case OSMO_TRAU16_FT_EFR: - return encode16_fr(bits, fr); + return encode16_fr(bits, fr, false); case OSMO_TRAU16_FT_HR: return encode16_hr(bits, fr); case OSMO_TRAU16_FT_AMR: - return encode16_amr(bits, fr); + return encode16_amr(bits, fr, false); case OSMO_TRAU16_FT_OAM: return encode16_oam(bits, fr); case OSMO_TRAU16_FT_IDLE: @@ -1305,7 +1329,7 @@ case OSMO_TRAU16_FT_EDATA: return encode16_edata(bits, fr); case OSMO_TRAU8_SPEECH: - return encode8_hr(bits, fr); + return encode8_hr(bits, fr, false); case OSMO_TRAU8_DATA: return encode8_data(bits, fr); case OSMO_TRAU8_OAM: @@ -1322,6 +1346,63 @@ } }
+/*! Encode a TFO frame from its decoded representation to a sequence of unpacked bits. + * \param[out] bits caller-allocated buffer for unpacked outpud bits + * \param[in] n_bits size of 'bits' output buffer in number of unpacked bits + * \param[in] fr decoded representation of TRAU frame to be encoded + * \return 0 number of unpacked output bits generated; negative in case of error + * + * Compared to regular osmo_trau_frame_encode(), this TFO-specific TRAU frame + * encoding function restricts the set of possible frame types to those that + * are valid for TFO, restricts the direction to TRAU-UL, reduces the output + * space requirement (there is no timing alignment extension) and always uses + * all fr->c_bits provided by the application. + */ +int osmo_trau_frame_encode_tfo(ubit_t *bits, size_t n_bits, const struct osmo_trau_frame *fr) +{ + /* TFO frames are TRAU-UL only */ + if (fr->dir != OSMO_TRAU_DIR_UL) + return -EINVAL; + + /* check for sufficient space provided by caller in output buffer */ + /* there is no timing alignment in TRAU-UL direction! */ + switch (fr->type) { + case OSMO_TRAU16_FT_FR: + case OSMO_TRAU16_FT_EFR: + case OSMO_TRAU16_FT_AMR: + if (n_bits < 1 * 40 * 8) + return -ENOSPC; + break; + case OSMO_TRAU8_SPEECH: + case OSMO_TRAU8_AMR_LOW: + case OSMO_TRAU8_AMR_6k7: + case OSMO_TRAU8_AMR_7k4: + if (n_bits < 1 * 20 * 8) + return -ENOSPC; + break; + default: + return -EINVAL; + } + + switch (fr->type) { + case OSMO_TRAU16_FT_FR: + case OSMO_TRAU16_FT_EFR: + return encode16_fr(bits, fr, true); + case OSMO_TRAU16_FT_AMR: + return encode16_amr(bits, fr, true); + case OSMO_TRAU8_SPEECH: + return encode8_hr(bits, fr, true); + case OSMO_TRAU8_AMR_LOW: + return encode8_amr_low(bits, fr); + case OSMO_TRAU8_AMR_6k7: + return encode8_amr_67(bits, fr); + case OSMO_TRAU8_AMR_7k4: + return encode8_amr_74(bits, fr); + default: + return -EINVAL; + } +} + /*! Decode/parse a 16k TRAU frame from unpacked bits to decoded format. * \param[out] fr caller-allocated output data structure * \param[in] bits unpacked bits containing raw TRAU frame; must be aligned
-
falconia