SIP Inspector
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Video

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Version 7 can offer, send and receive H.264 video together with audio in one call.

Figure 28 - The Video tab during a video call: the picture received from the other side, with its size, frame rate and bit rate
Figure 28 - The Video tab during a video call: the picture received from the other side, with its size, frame rate and bit rate

The Video tab

  • The picture area and three lines of text show the received stream: size, frames per second, kbit/s, how many pictures were decoded and the problems found (lost packets and the like).
  • Process video packets. Decoding takes processing power, so it is off by default: the received video is counted and dropped. The calls still offer a video port, send video and ask the remote side to send it. Tick the box to see the picture. It is the same as the command line option -pv.
  • Wait for ... pictures, max ... s with the left arrow adds a Wait video entry to the scenario (the same entry as in the Command tab).
  • Large view... opens the picture in a window of its own. The scenario screen has a Video button for the same (it appears when video is processed).

Video in a scenario

Three things make a video call:

  1. The SDP has a video media line. The keyword [video_port] is the port the program has opened for the video of this call (example below).
  2. Sending video. A ‘Play pcap’ entry with ;video=true sends a pcap file with H.264 RTP as video. The file can also be an MP4 file with H.264 video: the program reads it and sends the H.264 as RTP packets. Nothing is decoded or encoded for that. The audio of an MP4 file is ignored.
  3. Receiving video. The program starts a receiver on the video port. It puts the packets in order, builds the H.264 pictures (RFC 6184) and decodes them. Wait video holds the call until a number of pictures has been decoded.

The media lines of an SDP with audio and video:

m=audio [media_port] RTP/AVP 0 101
a=rtpmap:0 PCMU/8000
...
m=video [video_port] RTP/AVP 96
a=rtpmap:96 H264/90000
a=fmtp:96 profile-level-id=420028;packetization-mode=1
a=sendrecv

After the ACK a client plays audio and video and waits for the incoming pictures (this is Call_video_client.txt; the server Call_video_server.txt sends its video from an MP4 file):

---> ACK
---- Play pcap=./pcap/test.pcap
---- Play pcap=./pcap/video_h264.pcap;video=true
---- waitVideo=30
---- Pause[ms]=1500
---> BYE
Figure 29 - The scenario screen of a video call. The Video button shows the picture in its own window
Figure 29 - The scenario screen of a video call. The Video button shows the picture in its own window

Your own video. Put an MP4 (or MOV) file with H.264 video in the pcap folder and run test/mp4_info.sh pcap/clip.mp4. It tells what the program will send (size, frames per second, length, key frames) and prints the video lines for the SDP of the scenario, with the profile-level-id and the sprop-parameter-sets of that file. Files with another codec, without a key frame, cut off or larger than 200 MB are refused.

Note: The video is a test tool for signalling and media paths. A real stream (High profile, 720p and larger, many reference frames) may decode slower or not at all with the decoder that is built into the program. The sent video is never re-encoded, so it always looks like the file.