rtpbin: change how NTP time is calculated in RTCP
Don't calculate the NTP time based on the running_time of the pipeline but from
the systemclock. This allows us to generate more accurate NTP timestamps in case
the systemclock is synchronized with NTP or similar.
diff --git a/gst/rtpmanager/rtpsource.c b/gst/rtpmanager/rtpsource.c
index 6a46873..ed4c433 100644
--- a/gst/rtpmanager/rtpsource.c
+++ b/gst/rtpmanager/rtpsource.c
@@ -1047,8 +1047,7 @@
* @src: an #RTPSource
* @data: an RTP buffer or a list of RTP buffers
* @is_list: if @data is a buffer or list
- * @ntpnstime: the NTP time when this buffer was captured in nanoseconds. This
- * is the buffer timestamp converted to NTP time.
+ * @running_time: the running time of @data
*
* Send @data (an RTP buffer or list of buffers) originating from @src.
* This will make @src a sender. This function takes ownership of @data and
@@ -1058,13 +1057,13 @@
*/
GstFlowReturn
rtp_source_send_rtp (RTPSource * src, gpointer data, gboolean is_list,
- guint64 ntpnstime)
+ GstClockTime running_time)
{
GstFlowReturn result;
guint len;
guint32 rtptime;
guint64 ext_rtptime;
- guint64 ntp_diff, rtp_diff;
+ guint64 rt_diff, rtp_diff;
guint64 elapsed;
GstBufferList *list = NULL;
GstBuffer *buffer = NULL;
@@ -1104,8 +1103,8 @@
src->stats.octets_sent += len;
src->bytes_sent += len;
- if (src->prev_ntpnstime) {
- elapsed = ntpnstime - src->prev_ntpnstime;
+ if (src->prev_rtime) {
+ elapsed = running_time - src->prev_rtime;
if (elapsed > (G_GINT64_CONSTANT (1) << 31)) {
guint64 rate;
@@ -1122,12 +1121,12 @@
else
src->bitrate = ((src->bitrate * 3) + rate) / 4;
- src->prev_ntpnstime = ntpnstime;
+ src->prev_rtime = running_time;
src->bytes_sent = 0;
}
} else {
GST_LOG ("Reset bitrate measurement");
- src->prev_ntpnstime = ntpnstime;
+ src->prev_rtime = running_time;
src->bitrate = 0;
}
@@ -1139,24 +1138,24 @@
ext_rtptime = src->last_rtptime;
ext_rtptime = gst_rtp_buffer_ext_timestamp (&ext_rtptime, rtptime);
- GST_LOG ("SSRC %08x, RTP %" G_GUINT64_FORMAT ", NTP %" GST_TIME_FORMAT,
- src->ssrc, ext_rtptime, GST_TIME_ARGS (ntpnstime));
+ GST_LOG ("SSRC %08x, RTP %" G_GUINT64_FORMAT ", running_time %"
+ GST_TIME_FORMAT, src->ssrc, ext_rtptime, GST_TIME_ARGS (running_time));
if (ext_rtptime > src->last_rtptime) {
rtp_diff = ext_rtptime - src->last_rtptime;
- ntp_diff = ntpnstime - src->last_ntpnstime;
+ rt_diff = running_time - src->last_rtime;
/* calc the diff so we can detect drift at the sender. This can also be used
* to guestimate the clock rate if the NTP time is locked to the RTP
* timestamps (as is the case when the capture device is providing the clock). */
- GST_LOG ("SSRC %08x, diff RTP %" G_GUINT64_FORMAT ", diff NTP %"
- GST_TIME_FORMAT, src->ssrc, rtp_diff, GST_TIME_ARGS (ntp_diff));
+ GST_LOG ("SSRC %08x, diff RTP %" G_GUINT64_FORMAT ", diff running_time %"
+ GST_TIME_FORMAT, src->ssrc, rtp_diff, GST_TIME_ARGS (rt_diff));
}
/* we keep track of the last received RTP timestamp and the corresponding
- * NTP timestamp so that we can use this info when constructing SR reports */
+ * buffer running_time so that we can use this info when constructing SR reports */
+ src->last_rtime = running_time;
src->last_rtptime = ext_rtptime;
- src->last_ntpnstime = ntpnstime;
/* push packet */
if (!src->callbacks.push_rtp)
@@ -1312,6 +1311,7 @@
* rtp_source_get_new_sr:
* @src: an #RTPSource
* @ntpnstime: the current time in nanoseconds since 1970
+ * @running_time: the current running_time of the pipeline.
* @ntptime: the NTP time in 32.32 fixed point
* @rtptime: the RTP time corresponding to @ntptime
* @packet_count: the packet count
@@ -1319,12 +1319,19 @@
*
* Get new values to put into a new SR report from this source.
*
+ * @running_time and @ntpnstime are captured at the same time and represent the
+ * running time of the pipeline clock and the absolute current system time in
+ * nanoseconds respectively. Together with the last running_time and rtp timestamp
+ * we have observed in the source, we can generate @ntptime and @rtptime for an SR
+ * packet. @ntptime is basically the fixed point representation of @ntpnstime
+ * and @rtptime the associated RTP timestamp.
+ *
* Returns: %TRUE on success.
*/
gboolean
rtp_source_get_new_sr (RTPSource * src, guint64 ntpnstime,
- guint64 * ntptime, guint32 * rtptime, guint32 * packet_count,
- guint32 * octet_count)
+ GstClockTime running_time, guint64 * ntptime, guint32 * rtptime,
+ guint32 * packet_count, guint32 * octet_count)
{
guint64 t_rtp;
guint64 t_current_ntp;
@@ -1332,30 +1339,36 @@
g_return_val_if_fail (RTP_IS_SOURCE (src), FALSE);
- /* use the sync params to interpolate the date->time member to rtptime. We
- * use the last sent timestamp and rtptime as reference points. We assume
- * that the slope of the rtptime vs timestamp curve is 1, which is certainly
+ /* We last saw a buffer with last_rtptime at last_rtime. Given a running_time
+ * and an NTP time, we can scale the RTP timestamps so that they match the
+ * given NTP time. for scaling, we assume that the slope of the rtptime vs
+ * running_time vs ntptime curve is close to 1, which is certainly
* sufficient for the frequency at which we report SR and the rate we send
* out RTP packets. */
t_rtp = src->last_rtptime;
- GST_DEBUG ("last_ntpnstime %" GST_TIME_FORMAT ", last_rtptime %"
- G_GUINT64_FORMAT, GST_TIME_ARGS (src->last_ntpnstime), t_rtp);
+ GST_DEBUG ("last_rtime %" GST_TIME_FORMAT ", last_rtptime %"
+ G_GUINT64_FORMAT, GST_TIME_ARGS (src->last_rtime), t_rtp);
if (src->clock_rate != -1) {
- /* get the diff with the SR time */
- diff = GST_CLOCK_DIFF (src->last_ntpnstime, ntpnstime);
+ /* get the diff between the clock running_time and the buffer running_time.
+ * This is the elapsed time, as measured against the pipeline clock, between
+ * when the rtp timestamp was observed and the current running_time.
+ *
+ * We need to apply this diff to the RTP timestamp to get the RTP timestamp
+ * for the given ntpnstime. */
+ diff = GST_CLOCK_DIFF (src->last_rtime, running_time);
/* now translate the diff to RTP time, handle positive and negative cases.
* If there is no diff, we already set rtptime correctly above. */
if (diff > 0) {
- GST_DEBUG ("ntpnstime %" GST_TIME_FORMAT ", diff %" GST_TIME_FORMAT,
- GST_TIME_ARGS (ntpnstime), GST_TIME_ARGS (diff));
+ GST_DEBUG ("running_time %" GST_TIME_FORMAT ", diff %" GST_TIME_FORMAT,
+ GST_TIME_ARGS (running_time), GST_TIME_ARGS (diff));
t_rtp += gst_util_uint64_scale_int (diff, src->clock_rate, GST_SECOND);
} else {
diff = -diff;
- GST_DEBUG ("ntpnstime %" GST_TIME_FORMAT ", diff -%" GST_TIME_FORMAT,
- GST_TIME_ARGS (ntpnstime), GST_TIME_ARGS (diff));
+ GST_DEBUG ("running_time %" GST_TIME_FORMAT ", diff -%" GST_TIME_FORMAT,
+ GST_TIME_ARGS (running_time), GST_TIME_ARGS (diff));
t_rtp -= gst_util_uint64_scale_int (diff, src->clock_rate, GST_SECOND);
}
} else {
