mgcp: Add transcoding from PCMU as well

Use the existing ulaw encode/decode to support PCMU as well.
The MERA VoIP switch has some severe issues with the GSM codec
and it appears easier to enable transcoding for it.

The mera switch doesn't appear to cope with codec change
between a SIP 180 trying and the 200 ok connection result.

Inserting the codec is touching too many places. Ideally we
should have the transcoding function as pointer in the struct
as well but the arguments differ.. so it is not a direct way
forward.

1 files changed, 26 insertions, 0 deletions

diff --git a/openbsc/src/libmgcp/mgcp_transcode.c b/openbsc/src/libmgcp/mgcp_transcode.c
index 12cce2616..c994d3291 100644
--- a/openbsc/src/libmgcp/mgcp_transcode.c
+++ b/openbsc/src/libmgcp/mgcp_transcode.c
@@ -52,6 +52,8 @@ static enum audio_format get_audio_format(const struct mgcp_rtp_codec *codec)
 			return AF_GSM;
 		if (!strcasecmp("PCMA", codec->subtype_name))
 			return AF_PCMA;
+		if (!strcasecmp("PCMU", codec->subtype_name))
+			return AF_PCMU;
 #ifdef HAVE_BCG729
 		if (!strcasecmp("G729", codec->subtype_name))
 			return AF_G729;
@@ -61,6 +63,8 @@ static enum audio_format get_audio_format(const struct mgcp_rtp_codec *codec)
 	}
 
 	switch (codec->payload_type) {
+	case 0 /* PCMU */:
+		return AF_PCMU;
 	case 3 /* GSM */:
 		return AF_GSM;
 	case 8 /* PCMA */:
@@ -102,6 +106,18 @@ static void alaw_decode(unsigned char *buf, short *sample, size_t n)
 		*(sample++) = alaw_to_s16(*(buf++));
 }
 
+static void ulaw_encode(short *sample, unsigned char *buf, size_t n)
+{
+	for (; n > 0; --n)
+		*(buf++) = s16_to_ulaw(*(sample++));
+}
+
+static void ulaw_decode(unsigned char *buf, short *sample, size_t n)
+{
+	for (; n > 0; --n)
+		*(sample++) = ulaw_to_s16(*(buf++));
+}
+
 static int processing_state_destructor(struct mgcp_process_rtp_state *state)
 {
 	switch (state->src_fmt) {
@@ -226,6 +242,7 @@ int mgcp_transcoding_setup(struct mgcp_endpoint *endp,
 		}
 		break;
 #endif
+	case AF_PCMU:
 	case AF_PCMA:
 		state->src_frame_size = 80;
 		state->src_samples_per_frame = 80;
@@ -264,6 +281,7 @@ int mgcp_transcoding_setup(struct mgcp_endpoint *endp,
 		}
 		break;
 #endif
+	case AF_PCMU:
 	case AF_PCMA:
 		state->dst_frame_size = 80;
 		state->dst_samples_per_frame = 80;
@@ -331,6 +349,10 @@ static int decode_audio(struct mgcp_process_rtp_state *state,
 			bcg729Decoder(state->src.g729_dec, *src, 0, state->samples + state->sample_cnt);
 			break;
 #endif
+		case AF_PCMU:
+			ulaw_decode(*src, state->samples + state->sample_cnt,
+				    state->src_samples_per_frame);
+			break;
 		case AF_PCMA:
 			alaw_decode(*src, state->samples + state->sample_cnt,
 				    state->src_samples_per_frame);
@@ -381,6 +403,10 @@ static int encode_audio(struct mgcp_process_rtp_state *state,
 				      state->samples + state->sample_offs, dst);
 			break;
 #endif
+		case AF_PCMU:
+			ulaw_encode(state->samples + state->sample_offs, dst,
+				    state->src_samples_per_frame);
+			break;
 		case AF_PCMA:
 			alaw_encode(state->samples + state->sample_offs, dst,
 				    state->src_samples_per_frame);