NTP Timestamp in DeepStream
==============================
DeepStream 5.0 supports the setting of NTP timestamps per frame. Calculated NTP timestamp is available in `ntp_timestamp` field of `NvDsFrameMeta`.
DeepStream calculates NTP timestamps in 2 ways:

1. Host system time as NTP timestamp - when the frame is received by the `NvStreamMux` plugin in the DeepStream pipeline.
 
 This method requires you to synchronize host system to NTP clock.
 To attach host system time as NTP timestamp, you'll need to set `attach-sys-ts` to `TRUE` on    `nvstreammux`.
 In the DeepStream reference app this can be done by setting `attach-sys-ts-as-ntp` config parameter to `1` in `[streammux]` group of the application configuration file.

2. NTP timestamp when attached at RTSP source - supported only if RTSP sources send RTCP Sender Reports (SR).

  To configure the pipeline to attach these timestamps:

  * Set `attach-sys-ts` to `FALSE` on `nvstreammux`. In DeepStream reference app this can be done by setting `attach-sys-ts-as-ntp` config parameter to 0 in `[streammux]` group of the application configuration file.
  * After creating an `"rtspsrc"` element or an `"uridecodebin"` element, application must call `configure_source_for_ntp_sync()` function and pass the `GstElement` pointer to this API. (Refer to `create_rtsp_src_bin()` in `deepstream_source_bin.c` file) The API internally configures the pipeline to parse sender report and calculate NTP timestamps for each frame.
  * Make sure RTSP source can send RTCP Sender Reports.

    Verify this by starting streaming from the source on a host and viewing the packets in a tool like wireshark or tshark on the same host to confirm the presence of Sender Reports (SR).

    Example method to check if RTSP source sends RTCP sender reports using a tool like tshark:

     .. note:: We assume RTSP source has IP address 192.168.1.100

     1. Install tshark on a host: ``sudo apt-get install tshark``

     2. Find the host network interface that would be receiving the RTP/RTCP packets: ::

           $ sudo tshark -D
           ...
           eno1
           ...

     3. Start the monitoring using tshark tool. Replace the network interface and source IP as applicable:
     ``$ sudo tshark -i eno1 -f "src host 192.168.1.100" -Y "rtcp"``

     4. On the same host, start streaming from the RTSP source only after starting the monitoring tool. Any client may be used:
     ``$ gst-launch-1.0 rtspsrc location= <RTSP URL e.g. rtsp://192.168.1.100/stream1> ! fakesink``

     5. The output of the tshark monitoring tool should have lines containing "Sender Report   Source description".  Sample output as follows:
     ``6041 10.500649319 192.168.1.100 → 192.168.1.101 RTCP 94 Sender Report   Source description``