diff options
| -rw-r--r-- | openbsc/src/libtrau/rtp_proxy.c | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/openbsc/src/libtrau/rtp_proxy.c b/openbsc/src/libtrau/rtp_proxy.c index d8fde15d1..e29f26ccf 100644 --- a/openbsc/src/libtrau/rtp_proxy.c +++ b/openbsc/src/libtrau/rtp_proxy.c @@ -210,6 +210,67 @@ static int rtp_decode(struct msgb *msg, uint32_t callref, struct msgb **data, in return 0; } +#define USEC_1S 1000000 +#define USEC_10MS 10000 +#define USEC_20MS 20000 +#define SAMPLES_1S 8000 +#define USEC_SAMPLE 125 + +/* add usec to tv */ +static void tv_add_usec(struct timeval *tv, long int usec) +{ + struct timeval tv_add; + + tv_add.tv_sec = usec / USEC_1S; + tv_add.tv_usec = usec % USEC_1S; + timeradd(tv, &tv_add, tv); +} + +static int correct_timestamp(struct rtp_socket *rs, int duration) +{ + struct timeval tv, tv_diff; + long int usec_diff, frame_diff; + int usec_duration = duration * USEC_SAMPLE; + + gettimeofday(&tv, NULL); + timersub(&tv, &rs->transmit.last_tv, &tv_diff); + + usec_diff = tv_diff.tv_sec * USEC_1S + tv_diff.tv_usec; + frame_diff = (usec_diff + (usec_duration >> 1)) / usec_duration; /* round */ + + /* Drop frame, if current time to too much in advance of the last_tv. + * < 0 means that the time difference in frames must be at lease 2 + * frames below the expected difference of 1. + */ + if (frame_diff < 0) + return -1; + + /* Increment last_tv by the duration of one frame. */ + tv_add_usec(&rs->transmit.last_tv, usec_duration); + + /* Increment last_tv, if the current time is too much afterwards. + * Also increment timestamp and sequence number of RTP socket state. + * > 2 means that the time difference in frames must be at least 2 + * frames above the expected difference of 1. + */ + if (frame_diff > 2) { + long int frame_diff_excess = frame_diff - 1; + long int sample_diff_excess = frame_diff_excess * duration; + + /* correct last_tv */ + tv_add_usec(&rs->transmit.last_tv, + sample_diff_excess * USEC_SAMPLE); + LOGP(DLMUX, LOGL_NOTICE, + "Correcting timestamp difference of %ld frames " + "(to %s)\n", frame_diff_excess, + (rs->rx_action == RTP_RECV_APP) ? "app" : "BTS"); + rs->transmit.sequence += frame_diff_excess; + rs->transmit.timestamp += sample_diff_excess; + } + + return 0; +} + /*! \brief encode and send a rtp frame * \param[in] rs RTP socket through which we shall send * \param[in] frame GSM RTP frame to be sent @@ -225,6 +286,7 @@ int rtp_send_frame(struct rtp_socket *rs, struct gsm_data_frame *frame) int duration; /* in samples */ int is_bfi = 0; uint8_t dynamic_pt = 0; + int rc; if (rs->rx_action == RTP_RECV_APP) dynamic_pt = rs->receive.payload_type; @@ -235,6 +297,7 @@ int rtp_send_frame(struct rtp_socket *rs, struct gsm_data_frame *frame) rs->transmit.ssrc = rand(); rs->transmit.sequence = random(); rs->transmit.timestamp = random(); + gettimeofday(&rs->transmit.last_tv, NULL); } switch (frame->msg_type) { @@ -276,6 +339,10 @@ int rtp_send_frame(struct rtp_socket *rs, struct gsm_data_frame *frame) return -EINVAL; } + rc = correct_timestamp(rs, duration); + if (rc) + return 0; + if (is_bfi) { /* In case of a bad frame, just count and drop packet. */ rs->transmit.timestamp += duration; |