hi all：

I am new for gstreamer.I use a pipeline to record mp4 files,the pipeline is as follow:

udpsrc1-->udph264depay1-->h264parse1--->...-->
                                                                    |-->videomixer-->mp4mux-->filesink
udpsrc2-->udph264depay2-->h264parse2-->....-->

And the video stream source is from a MCU,I can choose its bitrate.But  when the bitrate is below a value(for example 640),'videomixer' will not work.But the MCU's default value is 512 ,I can not modify it,and what should I do ?