I am trying to stream an mp4v / mp4a rtp stream. The pipeline is at the moment: ./test-launch --gst-debug-level=0 "( ximagesrc use-damage=false endx=640 endy=640 startx=100 starty=100 ! video/x-raw-rgb,framerate=10/1 ! queue max-size-buffers=5 ! ffmpegcolorspace ! videoscale ! video/x-raw-yuv,width=640,height=640 ! ffenc_mpeg4 ! queue ! rtpmp4vpay name=pay0 pt=96 ! rtpmux name=muxer name=pay0 pt=96 audiotestsrc is-live=true ! audio/x-raw-int,rate=(int)90000 ! faac ! audio/mpegversion=4 ! queue ! rtpmp4apay name=pay1 pt=97 ! muxer. muxer. )" The problem I am having is that the audio part is missing. If I remove the caps after the faac plugin, the audio is in the stream. When I look at the startup log I see a clock-rate of 44100 for the mp4a stream and a clock rate of 90000 for the mp4v stream. I am pretty sure this is what is wrong. If I stream with the caps for mpegversion=4 removed I see audio and video clockrates both = 90000. How do I get the clockrates to match up? I tried to increase the audio rate to 90000 but it increased to 88200. I tried to reduce the video clock rate but I could not get it to change.