falconia has uploaded this change for review.
trau2rtp: add CSD support
TRAU frame formats are defined for both speech and data; classic E1
BTSes implement CSD with TRAU data frames on Abis. Support converting
these TRAU data frames to RTP clearmode representation, essentially
replicating the Rate Adaptor part of standard TRAU.
Change-Id: Ibc062c7297899fab106b3dbab301e665422a0d8b
---
M src/trau/trau_rtp_conv.c
1 file changed, 120 insertions(+), 1 deletion(-)
git pull ssh://gerrit.osmocom.org:29418/libosmo-abis refs/changes/32/38132/1
diff --git a/src/trau/trau_rtp_conv.c b/src/trau/trau_rtp_conv.c
index d149264..9113f10 100644
--- a/src/trau/trau_rtp_conv.c
+++ b/src/trau/trau_rtp_conv.c
@@ -31,6 +31,9 @@
#include <osmocom/trau/trau_frame.h>
#include <osmocom/trau/trau_rtp.h>
+/* RFC4040 "clearmode" RTP payload length */
+#define RFC4040_RTP_PLEN 160
+
/* this corresponds to the bit-lengths of the individual codec
* parameters as indicated in Table 1.1 of TS 46.010 */
static const uint8_t gsm_fr_map[] = {
@@ -46,7 +49,6 @@
3, 3, 3, 3
};
-
/*
* EFR TRAU parity (also used for HR)
*
@@ -942,6 +944,117 @@
}
#endif
+/*
+ * CSD support: converting TRAU frames of type 'data' to 64 kbit/s
+ * like the RA part of TRAU, using RTP clearmode representation.
+ */
+
+static void trau2v110_bits(ubit_t *out, const ubit_t *in)
+{
+ int i;
+
+ /* the first 8 bits are sync zeros */
+ memset(out, 0, 8);
+ out += 8;
+ /* for the rest, we have to expand 63 bits into 72 */
+ for (i = 0; i < 9; i++) {
+ *out++ = 1;
+ memcpy(out, in, 7);
+ in += 7;
+ out += 7;
+ }
+}
+
+/* intermediate rate 8 kbit/s */
+static void trau2v110_ir8(uint8_t *out, const ubit_t *in)
+{
+ ubit_t ra_bits[80];
+ int i;
+
+ trau2v110_bits(ra_bits, in);
+
+ /* RA2: 1 bit per output byte */
+ for (i = 0; i < 80; i++)
+ out[i] = 0x7F | (ra_bits[i] << 7);
+}
+
+/* intermediate rate 16 kbit/s */
+static void trau2v110_ir16(uint8_t *out, const ubit_t *in)
+{
+ ubit_t ra_bits[80];
+ int i, o;
+ uint8_t b;
+
+ trau2v110_bits(ra_bits, in);
+
+ /* RA2: 2 bits per output byte */
+ i = 0;
+ for (o = 0; o < 40; o++) {
+ b = 0x3F;
+ b |= (ra_bits[i++] << 7);
+ b |= (ra_bits[i++] << 6);
+ out[o] = b;
+ }
+}
+
+static int trau2rtp_data_fr(uint8_t *out, size_t out_len,
+ const struct osmo_trau_frame *tf)
+{
+ /* function interface preliminaries */
+ if (tf->type != OSMO_TRAU16_FT_DATA)
+ return -EINVAL;
+ if (out_len < RFC4040_RTP_PLEN)
+ return -ENOSPC;
+
+ /* Is it TCH/F9.6 with 16 kbit/s IR,
+ * or TCH/F4.8 or TCH/F2.4 with 8 kbit/s IR? */
+ if (tf->c_bits[5]) {
+ trau2v110_ir16(out, tf->d_bits);
+ trau2v110_ir16(out + 40, tf->d_bits + 63);
+ trau2v110_ir16(out + 80, tf->d_bits + 63 * 2);
+ trau2v110_ir16(out + 120, tf->d_bits + 63 * 3);
+ } else {
+ trau2v110_ir8(out, tf->d_bits);
+ trau2v110_ir8(out + 80, tf->d_bits + 63 * 2);
+ }
+
+ return RFC4040_RTP_PLEN;
+}
+
+static int trau2rtp_data_hr16(uint8_t *out, size_t out_len,
+ const struct osmo_trau_frame *tf)
+{
+ /* function interface preliminaries */
+ if (tf->type != OSMO_TRAU16_FT_DATA_HR)
+ return -EINVAL;
+ if (out_len < RFC4040_RTP_PLEN)
+ return -ENOSPC;
+
+ /* Note that Osmocom trau_frame decoding and encoding API
+ * puts the second reduced V.110 frame at d_bits position 63,
+ * unlike 8 kbit/s IR in FR-data frame type where it resides
+ * at d_bits position 63 * 2. */
+ trau2v110_ir8(out, tf->d_bits);
+ trau2v110_ir8(out + 80, tf->d_bits + 63);
+
+ return RFC4040_RTP_PLEN;
+}
+
+static int trau2rtp_data_hr8(uint8_t *out, size_t out_len,
+ const struct osmo_trau_frame *tf)
+{
+ /* function interface preliminaries */
+ if (tf->type != OSMO_TRAU8_DATA)
+ return -EINVAL;
+ if (out_len < RFC4040_RTP_PLEN)
+ return -ENOSPC;
+
+ trau2v110_ir8(out, tf->d_bits);
+ trau2v110_ir8(out + 80, tf->d_bits + 63);
+
+ return RFC4040_RTP_PLEN;
+}
+
static inline bool check_twts001(struct osmo_trau2rtp_state *st)
{
if (st->rtp_extensions & OSMO_RTP_EXT_TWTS001)
@@ -968,8 +1081,14 @@
return trau2rtp_efr(out, out_len, tf, check_twts001(st));
case OSMO_TRAU16_FT_HR:
return trau2rtp_hr16(out, out_len, tf, check_twts002(st));
+ case OSMO_TRAU16_FT_DATA:
+ return trau2rtp_data_fr(out, out_len, tf);
+ case OSMO_TRAU16_FT_DATA_HR:
+ return trau2rtp_data_hr16(out, out_len, tf);
case OSMO_TRAU8_SPEECH:
return trau2rtp_hr8(out, out_len, tf, check_twts002(st));
+ case OSMO_TRAU8_DATA:
+ return trau2rtp_data_hr8(out, out_len, tf);
default:
return -EINVAL;
}
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