Sysmobts L1: Implement HR codec support

We don't really know if the HR encoding is compatible with other
equipment, but it _should_ follow Chapter 5.2 of ETSI TS 101 318.

Please note that RFC5993 also specifies a way to encode GSM-HR into RTP,
we do not try to be compatible with that.  The only difference seems to
be one additional TOC octet at the beginning of the payload field.

1 files changed, 22 insertions, 3 deletions

diff --git a/src/osmo-bts-sysmo/tch.c b/src/osmo-bts-sysmo/tch.c
index 6710edd..1225010 100644
--- a/src/osmo-bts-sysmo/tch.c
+++ b/src/osmo-bts-sysmo/tch.c
@@ -158,10 +158,18 @@ static struct msgb *l1_to_rtppayload_hr(uint8_t *l1_payload, uint8_t payload_len
 	struct msgb *msg = msgb_alloc_headroom(1024, 128, "L1C-to-RTP");
 	uint8_t *cur;
 
-#warning Test GSM HR
+	if (payload_len != GSM_HR_BYTES) {
+		LOGP(DL1C, LOGL_ERROR, "L1 HR frame length %u != expected %u\n",
+			payload_len, GSM_HR_BYTES);
+		return NULL;
+	}
+
 	cur = msgb_put(msg, GSM_HR_BYTES);
 	memcpy(cur, l1_payload, GSM_HR_BYTES);
 
+	/* reverse the bit-order of each payload byte */
+	osmo_revbytebits_buf(cur, GSM_HR_BYTES);
+
 	return msg;
 }
 
@@ -174,8 +182,19 @@ static struct msgb *l1_to_rtppayload_hr(uint8_t *l1_payload, uint8_t payload_len
 static int rtppayload_to_l1_hr(uint8_t *l1_payload, uint8_t *rtp_payload,
 				unsigned int payload_len)
 {
-#warning Implement GSM HR
-	return 0;
+
+	if (payload_len != GSM_HR_BYTES) {
+		LOGP(DL1C, LOGL_ERROR, "RTP HR frame length %u != expected %u\n",
+			payload_len, GSM_HR_BYTES);
+		return 0;
+	}
+
+	memcpy(l1_payload, rtp_payload, GSM_HR_BYTES);
+
+	/* reverse the bit-order of each payload byte */
+	osmo_revbytebits_buf(l1_payload, GSM_HR_BYTES);
+
+	return GSM_HR_BYTES;
 }
 
 #define AMR_TOC_QBIT	0x04