GStreamer. How to share v4l2src?

Question

I didn't know that using one webcam with multiple programs at the same time was a problem.

My program has two components that use v4l2src:

1. Preview yourself;
2. Sending to udpsink.

I hoped to achieve this with appsrc/appsink:

• Create a common webcam component that inside has a pipeline:
  v4l2src ! video/x-raw,width=640,height=480 ! appsink,
  and has a method setupAppSrc for other components that need to use it.

• PreviewSelf has a pipeline:
  appsrc ! videoconvert ! xvimagesink.

• VideoSender has a pipeline:
  appsrc ! videoconvert ! x264enc ! h264parse ! rtph264pay ! application/x-rtp, media=video, encoding-name=H264, payload=96 ! udpsink.

appsink has a signal new-sample. Let's connect to it, receive the data using gst_app_sink_pull_sample and send it to the installed GstAppSrc using gst_app_src_push_sample.

Possible create multiple PreviewSelf and they will work well. But as soon as I add a VideoSender, everything freezes.

I tried to do:
gst-launch-1.0 v4l2src ! video/x-raw,width=640,height=480 ! tee name=mux \
mux. ! queue ! videoconvert ! xvimagesink \
mux. ! queue ! videoconvert ! x264enc ! fakesink
And It freezes too.

Tell me, please, how several components can use a webcam?

Answer 1

Your queues are too small for your tee pipeline. Increase them or use tune=zerolatency for the x264enc element.