title: Multiple H.264 video streams in one RTP session
body: <p>I would like to dynamically switch the video source in a streaming video application. However, the different video sources have unique image dimensions. I can generate individual SDP files for each video source, but I would like to combine them into a single SDP file so that the viewing client could automatically resize the display window as the video source changed. Here are two example SDP files:</p>
  
  <p>640x480.sdp:</p>
  
  <pre>
  v=0
  o=VideoServer 305419896 9876543210 IN IP4 192.168.0.2
  s=VideoStream640x480
  t=0 0
  c=IN IP4 192.168.0.2
  m=video 8000/2 RTP/AVP 96
  a=rtpmap:96 H264/90000
  a=fmtp:96 packetization-mode=0; profile-level-id=4D4033; sprop-parameter-sets=Z01AM5ZkBQHtCAAAAwAIAAADAYR4wZU=,aO48gJ==
  a=control:trackID=1
  </pre>
  
  <p>960x480.sdp:</p>
  
  <pre>
  v=0
  o=VideoServer 305419896 9876543210 IN IP4 192.168.0.2
  s=VideoStream960x480
  t=0 0
  c=IN IP4 192.168.0.2
  m=video 8000/2 RTP/AVP 96
  a=rtpmap:96 H264/90000
  a=fmtp:96 packetization-mode=0; profile-level-id=4D4033; sprop-parameter-sets=J01AM5WwPA9sBAIA,KO4G8gA=
  a=control:trackID=1
  </pre>
  
  <p>How can these individual files be combined into a single SDP file?</p>