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[PATCH 8/9] Fixed (ipaccess BTS) delay/silence problems, if RTP stream jitters too much

by Andreas Eversberg

After OpenBSC stalled for some reason (e.g. CPU overload or database access) or after speech frames have been lost (MNCC application problems / hold/retrieve call), the timestamp and the sequence number of the RTP socket state must be corrected. The amount of incrmentation is calculated from the elapsed time. Not incrementing timestamp and sequence number would cause all frames to be dropped by ipaccess BTS, because the BTS expects frames with more recent timestamps. If speech frames are received too fast, they must be dropped. The timestamp and sequence number of the RTP socket state are not changed in this case. Incmenetating timestamp and sequence number would causes high delay at ipaccess BTS, because the BTS would queue the frames until the timestamp matches the current time. There is a simple test case: Make a call between two phones and check the delay. (When using LCR, make a call to the echo test.) The press CTRL+z to suspend OpenBSC process for a few seconds and enter "fg" to continue OpenBSC process. There shall be no change in the delay, even after repeating this test many times. --- openbsc/src/libtrau/rtp_proxy.c | 89 +++++++++++++++++++++++++++-------------- 1 file changed, 60 insertions(+), 29 deletions(-) diff --git a/openbsc/src/libtrau/rtp_proxy.c b/openbsc/src/libtrau/rtp_proxy.c index 0c4d82b..fa6b629 100644 --- a/openbsc/src/libtrau/rtp_proxy.c +++ b/openbsc/src/libtrau/rtp_proxy.c @@ -236,19 +236,65 @@ static int rtp_decode(struct msgb *msg, uint32_t callref, struct msgb **data, in return 0; } -/* "to - from" */ -static void tv_difference(struct timeval *diff, const struct timeval *from, - const struct timeval *__to) +#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 _to = *__to, *to = &_to; + struct timeval tv_add; - if (to->tv_usec < from->tv_usec) { - to->tv_sec -= 1; - to->tv_usec += 1000000; + 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; } - diff->tv_usec = to->tv_usec - from->tv_usec; - diff->tv_sec = to->tv_sec - from->tv_sec; + return 0; } /*! \brief encode and send a rtp frame @@ -265,6 +311,7 @@ int rtp_send_frame(struct rtp_socket *rs, struct gsm_data_frame *frame) int duration; /* in samples */ int is_amr = 0, is_bfi = 0; uint8_t dynamic_pt = 0; + int rc; if (rs->rx_action == RTP_RECV_APP) dynamic_pt = rs->receive.payload_type; @@ -275,6 +322,7 @@ 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) { @@ -311,26 +359,9 @@ int rtp_send_frame(struct rtp_socket *rs, struct gsm_data_frame *frame) return -EINVAL; } - { - struct timeval tv, tv_diff; - long int usec_diff, frame_diff; - - gettimeofday(&tv, NULL); - tv_difference(&tv_diff, &rs->transmit.last_tv, &tv); - rs->transmit.last_tv = tv; - - usec_diff = tv_diff.tv_sec * 1000000 + tv_diff.tv_usec; - frame_diff = (usec_diff / 20000); - - if (abs(frame_diff) > 1) { - long int frame_diff_excess = frame_diff - 1; - - LOGP(DLMUX, LOGL_NOTICE, - "Correcting frame difference of %ld frames\n", frame_diff_excess); - rs->transmit.sequence += frame_diff_excess; - rs->transmit.timestamp += frame_diff_excess * duration; - } - } + rc = correct_timestamp(rs, duration); + if (rc) + return 0; if (is_bfi) { /* In case of a bad frame, just count and drop packt. */ -- 1.8.1.5 --------------070804050601000205010809--

13 years, 4 months

[PATCH 8/9] Fixed (nanoBTS) delay problems, if RTP stream jitters too much

by Andreas Eversberg

The RTP stream is generated or forwarded by OpenBSC to nanoBTS. Due to switching of streams (hold/retrieve call), packet loss or even stalling of sender's process, the time stamp must be corrected. If outdated packets are received, they get dropped. --- openbsc/src/libtrau/rtp_proxy.c | 80 ++++++++++++++++++++++++++++++----------- 1 file changed, 59 insertions(+), 21 deletions(-) diff --git a/openbsc/src/libtrau/rtp_proxy.c b/openbsc/src/libtrau/rtp_proxy.c index ed7479d..3e6c462 100644 --- a/openbsc/src/libtrau/rtp_proxy.c +++ b/openbsc/src/libtrau/rtp_proxy.c @@ -236,6 +236,12 @@ 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 + /* "to - from" */ static void tv_difference(struct timeval *diff, const struct timeval *from, const struct timeval *__to) @@ -244,13 +250,60 @@ static void tv_difference(struct timeval *diff, const struct timeval *from, if (to->tv_usec < from->tv_usec) { to->tv_sec -= 1; - to->tv_usec += 1000000; + to->tv_usec += USEC_1S; } diff->tv_usec = to->tv_usec - from->tv_usec; diff->tv_sec = to->tv_sec - from->tv_sec; } +/* add sec,usec to tv */ +static void tv_add(struct timeval *tv, int sec, int usec) +{ + + if (usec < 0) + usec += USEC_1S; + tv->tv_sec += sec; + tv->tv_usec += usec; + if (tv->tv_usec >= USEC_1S) { + tv->tv_sec++; + tv->tv_usec -= USEC_1S; + } +} + +static int correct_timestamp(struct rtp_socket *rs, int duration) +{ + struct timeval tv, tv_diff; + long int usec_diff, frame_diff; + + gettimeofday(&tv, NULL); + tv_difference(&tv_diff, &rs->transmit.last_tv, &tv); + tv_add(&rs->transmit.last_tv, 0, USEC_20MS); + + usec_diff = tv_diff.tv_sec * USEC_1S + tv_diff.tv_usec; + frame_diff = ((usec_diff + (USEC_10MS)) / USEC_20MS); /* round */ + + if (abs(frame_diff - 1) > 1) { + long int frame_diff_excess = frame_diff - 1; + long int sample_diff_excess = frame_diff_excess * duration; + + /* correct last_tv */ + tv_add(&rs->transmit.last_tv, sample_diff_excess / SAMPLES_1S, + (sample_diff_excess % SAMPLES_1S) * USEC_SAMPLE); + /* drop frame, if time stamp is in the past */ + if (frame_diff_excess < 0) + return -1; + LOGP(DLMUX, LOGL_NOTICE, + "Correcting timestamp difference of %ld frames " + "(to %s)\n", frame_diff_excess, + (rs->rx_action == RTP_RECV_L4) ? "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 @@ -265,6 +318,7 @@ int rtp_send_frame(struct rtp_socket *rs, struct gsm_data_frame *frame) int duration; /* in samples */ int amr = 0; uint8_t dynamic_pt = 0; + int rc; if (rs->rx_action == RTP_RECV_L4) dynamic_pt = rs->receive.payload_type; @@ -275,6 +329,7 @@ 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) { @@ -313,26 +368,9 @@ int rtp_send_frame(struct rtp_socket *rs, struct gsm_data_frame *frame) return -EINVAL; } - { - struct timeval tv, tv_diff; - long int usec_diff, frame_diff; - - gettimeofday(&tv, NULL); - tv_difference(&tv_diff, &rs->transmit.last_tv, &tv); - rs->transmit.last_tv = tv; - - usec_diff = tv_diff.tv_sec * 1000000 + tv_diff.tv_usec; - frame_diff = (usec_diff / 20000); - - if (abs(frame_diff) > 1) { - long int frame_diff_excess = frame_diff - 1; - - LOGP(DLMUX, LOGL_NOTICE, - "Correcting frame difference of %ld frames\n", frame_diff_excess); - rs->transmit.sequence += frame_diff_excess; - rs->transmit.timestamp += frame_diff_excess * duration; - } - } + rc = correct_timestamp(rs, duration); + if (rc) + return 0; if (frame->msg_type == GSM_BAD_FRAME) return 0; -- 1.8.1.5 --------------090106010400060202050508--

13 years, 4 months

[PATCH 8/9] Fixed (nanoBTS) delay problems, if RTP stream jitters too much

by Andreas Eversberg

The RTP stream is generated or forwarded by OpenBSC to nanoBTS. Due to switching of streams (hold/retrieve call), packet loss or even stalling of sender's process, the time stamp must be corrected. If outdated packets are received, they get dropped. --- openbsc/src/libtrau/rtp_proxy.c | 82 ++++++++++++++++++++++++++++++----------- 1 file changed, 61 insertions(+), 21 deletions(-) diff --git a/openbsc/src/libtrau/rtp_proxy.c b/openbsc/src/libtrau/rtp_proxy.c index 2284798..88753b6 100644 --- a/openbsc/src/libtrau/rtp_proxy.c +++ b/openbsc/src/libtrau/rtp_proxy.c @@ -236,6 +236,12 @@ 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 + /* "to - from" */ static void tv_difference(struct timeval *diff, const struct timeval *from, const struct timeval *__to) @@ -244,13 +250,62 @@ static void tv_difference(struct timeval *diff, const struct timeval *from, if (to->tv_usec < from->tv_usec) { to->tv_sec -= 1; - to->tv_usec += 1000000; + to->tv_usec += USEC_1S; } diff->tv_usec = to->tv_usec - from->tv_usec; diff->tv_sec = to->tv_sec - from->tv_sec; } +/* add sec,usec to tv */ +static void tv_add(struct timeval *tv, int sec, int usec) +{ + + while (usec < 0) { + usec += USEC_1S; + sec--; + } + tv->tv_sec += sec; + tv->tv_usec += usec; + while (tv->tv_usec >= USEC_1S) { + tv->tv_sec++; + tv->tv_usec -= USEC_1S; + } +} + +static int correct_timestamp(struct rtp_socket *rs, int duration) +{ + struct timeval tv, tv_diff; + long int usec_diff, frame_diff; + + gettimeofday(&tv, NULL); + tv_difference(&tv_diff, &rs->transmit.last_tv, &tv); + tv_add(&rs->transmit.last_tv, 0, USEC_20MS); + + usec_diff = tv_diff.tv_sec * USEC_1S + tv_diff.tv_usec; + frame_diff = ((usec_diff + (USEC_10MS)) / USEC_20MS); /* round */ + + if (abs(frame_diff - 1) > 1) { + long int frame_diff_excess = frame_diff - 1; + long int sample_diff_excess = frame_diff_excess * duration; + + /* correct last_tv */ + tv_add(&rs->transmit.last_tv, sample_diff_excess / SAMPLES_1S, + (sample_diff_excess % SAMPLES_1S) * USEC_SAMPLE); + /* drop frame, if time stamp is in the past */ + if (frame_diff_excess < 0) + return -1; + LOGP(DLMUX, LOGL_NOTICE, + "Correcting timestamp difference of %ld frames " + "(to %s)\n", frame_diff_excess, + (rs->rx_action == RTP_RECV_L4) ? "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 @@ -265,6 +320,7 @@ int rtp_send_frame(struct rtp_socket *rs, struct gsm_data_frame *frame) int duration; /* in samples */ int amr = 0; uint8_t dynamic_pt = 0; + int rc; if (rs->rx_action == RTP_RECV_L4) dynamic_pt = rs->receive.payload_type; @@ -275,6 +331,7 @@ 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) { @@ -313,26 +370,9 @@ int rtp_send_frame(struct rtp_socket *rs, struct gsm_data_frame *frame) return -EINVAL; } - { - struct timeval tv, tv_diff; - long int usec_diff, frame_diff; - - gettimeofday(&tv, NULL); - tv_difference(&tv_diff, &rs->transmit.last_tv, &tv); - rs->transmit.last_tv = tv; - - usec_diff = tv_diff.tv_sec * 1000000 + tv_diff.tv_usec; - frame_diff = (usec_diff / 20000); - - if (abs(frame_diff) > 1) { - long int frame_diff_excess = frame_diff - 1; - - LOGP(DLMUX, LOGL_NOTICE, - "Correcting frame difference of %ld frames\n", frame_diff_excess); - rs->transmit.sequence += frame_diff_excess; - rs->transmit.timestamp += frame_diff_excess * duration; - } - } + rc = correct_timestamp(rs, duration); + if (rc) + return 0; if (frame->msg_type == GSM_BAD_FRAME) return 0; -- 1.8.1.5 --------------000504080100090805040102--

13 years, 4 months

Bounce action notification

by mailman＠lists.osmocom.org

This is a Mailman mailing list bounce action notice: List: OpenBSC Member: philip.lansink(a)lan-consult.nl Action: Subscription disabled. Reason: Excessive or fatal bounces. The triggering bounce notice is attached below. Questions? Contact the Mailman site administrator at mailman(a)lists.osmocom.org.

13 years, 4 months

Information about OpenBsc

by Ludovic Fotso

Hello, My Name is Tassy Fotso, I study communication Technologies in Higher Institut of Sahel (Cameroon).please How can I do to get OpenBSC. thanks

13 years, 4 months

Smoke a CAMEL?

by Jay R. Worthington

Hi y'all, not really sure if this help on building a "full fledged hlr", but the current version 4 of yate supports the MAP part of SS7, as well as CAMEL... http://yate.null.ro/ Regards, Jay

13 years, 4 months

BSC_MGCP

by Nik Pakar

Dear all, Is this BSC_MGCP is functioning ? Is that mean Open_BSC can be act as a MGCP gateway and can control from a MGCP_CA ? Rgds Nik

13 years, 4 months

Re: GSM video lectures (en)

by thriveni

13 years, 4 months

MySQL for HLR

by Nik Pakar

Is it possible to use mysql for HLR. I can see some notes within the source. Rgds Nik

13 years, 4 months

OpenBSC-LCR integration

by Nik Pakar

When OpenBSC integrates with LCR, is it mean all call routing capabilities going to LCR including gsm-gsm on net calls. Or is it only external calls going to LCR while gsm-gsm calls routed within NITB Rgds Nik

13 years, 4 months

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