mgcp: Document transcoding semantic and follow it
Transcoding from GSM to PCMA can lead to the MGCP MGW sending
two PCMA packages with the same sequence number and timestamp.
Once with the encoded audio and once completely empty.
This is because "state->dst_packet_duration" is 0 in most cases
(unless a ptime is forced) and we attempt to encode audio even
if there are not enough samples. The encode_audio return will
return 0 in that case which is not trated as an error by the
mgcp network code.
Handle rc == 0 specially and document the semantic.
diff --git a/openbsc/include/openbsc/mgcp.h b/openbsc/include/openbsc/mgcp.h
index d4d6140..1790f84 100644
--- a/openbsc/include/openbsc/mgcp.h
+++ b/openbsc/include/openbsc/mgcp.h
@@ -87,6 +87,12 @@
typedef int (*mgcp_reset)(struct mgcp_trunk_config *cfg);
typedef int (*mgcp_rqnt)(struct mgcp_endpoint *endp, char tone);
+/**
+ * Return:
+ * < 0 in case no audio was processed
+ * >= 0 in case audio was processed. The remaining payload
+ * length will be returned.
+ */
typedef int (*mgcp_processing)(struct mgcp_endpoint *endp,
struct mgcp_rtp_end *dst_end,
char *data, int *len, int buf_size);
diff --git a/openbsc/src/libmgcp/mgcp_transcode.c b/openbsc/src/libmgcp/mgcp_transcode.c
index 296020c..ff20fb8 100644
--- a/openbsc/src/libmgcp/mgcp_transcode.c
+++ b/openbsc/src/libmgcp/mgcp_transcode.c
@@ -488,7 +488,14 @@
nsamples = state->sample_cnt;
rc = encode_audio(state, dst, buf_size, max_samples);
- if (rc <= 0)
+ /*
+ * There were no samples to encode?
+ * TODO: how does this work for comfort noise?
+ */
+ if (rc == 0)
+ return -ENOMSG;
+ /* Any other error during the encoding */
+ if (rc < 0)
return rc;
nsamples -= state->sample_cnt;
diff --git a/openbsc/tests/mgcp/mgcp_transcoding_test.c b/openbsc/tests/mgcp/mgcp_transcoding_test.c
index 404268a..27d7269 100644
--- a/openbsc/tests/mgcp/mgcp_transcoding_test.c
+++ b/openbsc/tests/mgcp/mgcp_transcoding_test.c
@@ -120,6 +120,24 @@
"\xD5\xA5\xA3\xA5\xD5\x25\x23\x25\xD5\xA5\xA3\xA5\xD5\x25\x23\x25"
"\xD5\xA5\xA3\xA5\xD5\x25\x23\x25\xD5\xA5\xA3\xA5\xD5\x25\x23\x25"
},
+ /* RTP: SeqNo=26527, TS=0 */
+ {0.020000, 92,
+ "\x80\x08\x67\x9f\x00\x00\x00\x00\x04\xaa\x67\x9f\xd5\xd5\xd5\xd5"
+ "\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5"
+ "\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5"
+ "\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5"
+ "\xd5\xd5\xd5\xd5\xd5\xd5\x55\x55\xd5\xd5\x55\x55\xd5\xd5\x55\x55"
+ "\xd5\xd5\xd5\x55\x55\xd5\xd5\xd5\x55\x55\xd5\xd5"
+ },
+ /* RTP: SeqNo=26528, TS=80 */
+ {0.020000, 92,
+ "\x80\x08\x67\xa0\x00\x00\x00\x50\x04\xaa\x67\x9f\x55\xd5\xd5\x55"
+ "\xd5\x55\xd5\xd5\xd5\x55\xd5\x55\xd5\xd5\x55\xd5\x55\xd5\x55\xd5"
+ "\x55\x55\xd5\x55\xd5\xd5\x55\x55\x55\x55\x55\xd5\xd5\x55\xd5\xd5"
+ "\xd5\x55\xd5\xd5\xd5\x55\x54\x55\xd5\xd5\x55\xd5\xd5\xd5\xd5\x55"
+ "\x54\x55\xd5\x55\xd5\x55\x55\x55\x55\x55\xd5\xd5\xd5\xd5\xd5\xd4"
+ "\xd5\x54\x55\xd5\xd4\xd5\x54\xd5\x55\xd5\xd5\xd5"
+ },
};
@@ -221,8 +239,9 @@
cont = mgcp_transcoding_process_rtp(endp, dst_end,
buf, &len, sizeof(buf));
if (cont < 0) {
- printf("processing failed: %s", strerror(-cont));
- abort();
+ printf("Nothing encoded due: %s\n", strerror(-cont));
+ talloc_free(ctx);
+ return -1;
}
if (len < 24) {
@@ -296,6 +315,56 @@
talloc_free(ctx);
}
+static void test_transcode_result(void)
+{
+ char buf[4096];
+ int len, res;
+ void *ctx;
+ struct mgcp_endpoint *endp;
+ struct mgcp_process_rtp_state *state;
+
+ {
+ /* from GSM to PCMA and same ptime */
+ given_configured_endpoint(160, 0, "gsm", "pcma", &ctx, &endp);
+ state = endp->bts_end.rtp_process_data;
+
+ /* result */
+ len = audio_packets_gsm[0].len;
+ memcpy(buf, audio_packets_gsm[0].data, len);
+ res = mgcp_transcoding_process_rtp(endp, &endp->bts_end, buf, &len, ARRAY_SIZE(buf));
+ OSMO_ASSERT(res == sizeof(struct rtp_hdr));
+ OSMO_ASSERT(state->sample_cnt == 0);
+
+ len = res;
+ res = mgcp_transcoding_process_rtp(endp, &endp->bts_end, buf, &len, ARRAY_SIZE(buf));
+ OSMO_ASSERT(res == -ENOMSG);
+
+ talloc_free(ctx);
+ }
+
+ {
+ /* from PCMA to GSM and wrong different ptime */
+ given_configured_endpoint(80, 160, "pcma", "gsm", &ctx, &endp);
+ state = endp->bts_end.rtp_process_data;
+
+ /* Add the first sample */
+ len = audio_packets_pcma[1].len;
+ memcpy(buf, audio_packets_pcma[1].data, len);
+ res = mgcp_transcoding_process_rtp(endp, &endp->bts_end, buf, &len, ARRAY_SIZE(buf));
+ OSMO_ASSERT(state->sample_cnt == 80);
+ OSMO_ASSERT(res < 0);
+
+ /* Add the second sample and it should be consumable */
+ len = audio_packets_pcma[2].len;
+ memcpy(buf, audio_packets_pcma[2].data, len);
+ res = mgcp_transcoding_process_rtp(endp, &endp->bts_end, buf, &len, ARRAY_SIZE(buf));
+ OSMO_ASSERT(state->sample_cnt == 0);
+ OSMO_ASSERT(res == sizeof(struct rtp_hdr));
+
+ talloc_free(ctx);
+ }
+}
+
static int test_repacking(int in_samples, int out_samples, int no_transcode)
{
char buf[4096] = {0x80, 0};
@@ -378,6 +447,7 @@
int main(int argc, char **argv)
{
+ int rc;
osmo_init_logging(&log_info);
printf("=== Transcoding Good Cases ===\n");
@@ -413,19 +483,22 @@
printf("=== Transcoding Bad Cases ===\n");
printf("Invalid size:\n");
- transcode_test("gsm", "pcma",
+ rc = transcode_test("gsm", "pcma",
(uint8_t *)audio_packets_gsm_invalid_size[0].data,
audio_packets_gsm_invalid_size[0].len);
+ OSMO_ASSERT(rc < 0);
printf("Invalid data:\n");
- transcode_test("gsm", "pcma",
+ rc = transcode_test("gsm", "pcma",
(uint8_t *)audio_packets_gsm_invalid_data[0].data,
audio_packets_gsm_invalid_data[0].len);
+ OSMO_ASSERT(rc < 0);
printf("Invalid payload type:\n");
- transcode_test("gsm", "pcma",
+ rc = transcode_test("gsm", "pcma",
(uint8_t *)audio_packets_gsm_invalid_ptype[0].data,
audio_packets_gsm_invalid_ptype[0].len);
+ OSMO_ASSERT(rc == 0);
printf("=== Repacking ===\n");
@@ -440,6 +513,7 @@
test_repacking(160, 100, 0);
test_repacking(160, 100, 1);
test_rtp_seq_state();
+ test_transcode_result();
return 0;
}
diff --git a/openbsc/tests/mgcp/mgcp_transcoding_test.ok b/openbsc/tests/mgcp/mgcp_transcoding_test.ok
index e06b0e1..7c1c8ce 100644
--- a/openbsc/tests/mgcp/mgcp_transcoding_test.ok
+++ b/openbsc/tests/mgcp/mgcp_transcoding_test.ok
@@ -144,19 +144,11 @@
Invalid size:
== Transcoding test ==
converting gsm -> pcma
-encoded:
- 80 03 00 01 00 00 00 a0 11 22 33 44 d4 7c e3 e9
- 62 50 39 f0 f8 b4 68 ea 6c 0e 81 1b 56 2a d5 bc
- 69 9c d1 f0 66 7a ec 49 7a
-counted: 0
+Nothing encoded due: No message of desired type
Invalid data:
== Transcoding test ==
converting gsm -> pcma
-encoded:
- 80 03 00 01 00 00 00 a0 11 22 33 44 ee ee ee ee
- ee ee ee ee ee ee ee ee ee ee ee ee ee ee ee ee
- ee ee ee ee ee ee ee ee ee ee ee ee ee
-counted: 0
+Nothing encoded due: No message of desired type
Invalid payload type:
== Transcoding test ==
converting gsm -> pcma