包含两个接收器的Tee的GStreamer管道失败

Question

Trying to implement GStreamer pipeline with Tee using following elements.

gst_bin_add_many(GST_BIN (pipeline), <rpicamsrc>, <capsfilter>, <h264parse>, tee, <queue>, <rtph264pay>, <fakesink>, <queue>, <avdec_h264>, <videoconvert>, <capsfilter>, <customplugin>, <fakesink>, nullptr);

For better understanding provided the element names. The purpose is to create Tee pipeline as follows:

rpicamsrc ! capsfilter ! h264parse ! tee name=t t. ! queue ! rtph264pay ! fakesink t. ! queue ! avdec_h264 ! videoconvert ! capsfilter ! customplugin ! fakesink

But it fails always and doesn't report any error. But no video frames are captured. After some testing identified that fails for even this simple pipeline:

gst_element_link_many ( <rpicamsrc>, <capsfilter>, <h264parse>, <rtph264pay>, <fakesink>, nullptr))

Interesting is if I remove second fakesink from that above gst_bin_add_many line of code it works. Not sure what's the problem with this. Tried to use a different sink like autovideosink but no luck. When it fails it doesn't receive GST message type GST_MESSAGE_ASYNC_DONE in gst bus, but for success case it does. Gets GST_STREAM_STATUS_TYPE_CREATE , GST_STREAM_STATUS_TYPE_ENTER and GST_MESSAGE_STREAM_START for both failure and success case. What I am doing wrong, any ideas?

Answer 1

gst_element_link_many() is a convenient wrapper for a non-branched pipeline, meaning that it links one from next, to next. It does not know that you want to link the tee element in the middle of the pipeline with multiple elements. For example in your case, it tries to connect the fakesink to the queue in the middle of your pipeline.

Easy way

You can use gst_parse_launch() to let GStreamer figure out what links to what.

By your hands

If you have an element like tee , you must use gst_element_link() or gst_element_link_pads() to tell GSreamer that which element connect to which.

It is possible to create two pipelines with gst_element_link_many() ,

rpicamsrc → capsfilter → h264parse → tee → queue → rtph264pay → fakesink

queue → avdec_h264 → videoconvert → capsfilter → customplugin→ fakesink

and then, link the tee element in the above to the below with gst_element_link_pads() .