Pipeline gstreamer does not start after going from PAUSED to PLAYING

[vcb1]

I have an application that can consume from 2 rstps for that I use two different pipelines and my idea is to play and pause one of them to change between them.

The code below shows a represenation of the code where i inizialize the two pipelines and then i just start one of them. Afterwards whenever i want the idea is to pause one od them and to start the other. The code works fine for the first change (i.e stop pipeline1 and start piline2, but when i want to stop pipeline2 and start again pipeline1 the image is frozen.

// callback function 
static GstPadProbeReturn my_function(GstPad *pad, GstPadProbeInfo *info, gpointer u_data)
{
    //in this function i have a way from other aplication to detect that i want a change in the pipeline
    if(pipeline==2){
       // stop pipeline 1
       stop(gst_pipeline_1);
       // change to pipeline 2
       change_pipeline(gst_pipeline_2);
    }else{
	// stop pipeline 2
        stop(gst_pipeline_2);
	// change to pipeline 1
        change_pipeline(gst_pipeline_optical);
    }
}


//function to start the pipeline
GstElement& start_pipeline(int pipeid)
{
  
  GstElement *pipe = nullptr; 
  //depending on the pipeid i get a different pipeline
  pipeline = "STRING WITH A PIPELINE"
  pipe = gst_parse_launch(pipeline.c_str(), &gerror);
  return *pipe;
}

// function to select the pipeline to use
void change_pipeline(GstElement *pipe)
{

    gst_pipeline = pipe;
    src_pad = gst_element_get_static_pad(conv, "src");
    gst_pad_add_probe(src_pad, GST_PAD_PROBE_TYPE_BUFFER, my_function, NULL, NULL);
    ret = gst_element_set_state((GstElement *)gst_pipeline, GST_STATE_PLAYING);
    g_usleep(1000);
    bus = gst_pipeline_get_bus(GST_PIPELINE(gst_pipeline));
    gst_bus_poll(bus, GST_MESSAGE_EOS, GST_CLOCK_TIME_NONE);
   
}

I have printed the status of the piplines and the PAUSE is working to go from pipeline 1 to piline 2

----- status pipeline1 ---
GstElement(capsfilter10), status = PAUSED, pending = VOID_PENDING
GstElement(capsfilter4), status = PAUSED, pending = VOID_PENDING
GstElement(capsfilter3), status = PAUSED, pending = VOID_PENDING
GstElement(capsfilter2), status = PAUSED, pending = VOID_PENDING
GstElement(capsfilter1), status = PAUSED, pending = VOID_PENDING
GstElement(udpsink0), status = PAUSED, pending = VOID_PENDING
GstElement(rtpvp9pay0), status = PAUSED, pending = VOID_PENDING
GstElement(nvv4l2vp9enc0), status = PAUSED, pending = VOID_PENDING
GstElement(queue0), status = PAUSED, pending = VOID_PENDING
GstElement(nvvconv1), status = PAUSED, pending = VOID_PENDING
GstElement(myconv), status = PAUSED, pending = VOID_PENDING
GstElement(nvv4l2decoder0), status = PAUSED, pending = VOID_PENDING
GstElement(rtph265depay0), status = PAUSED, pending = VOID_PENDING
GstElement(rtspsrc0), status = PAUSED, pending = VOID_PENDING
========================
----- status pipeline2 ---
GstElement(capsfilter9), status = PLAYING, pending = VOID_PENDING
GstElement(capsfilter8), status = PLAYING, pending = VOID_PENDING
GstElement(capsfilter7), status = PLAYING, pending = VOID_PENDING
GstElement(capsfilter6), status = PLAYING, pending = VOID_PENDING
GstElement(udpsink1), status = PLAYING, pending = VOID_PENDING
GstElement(rtpvp9pay1), status = PLAYING, pending = VOID_PENDING
GstElement(nvv4l2vp9enc1), status = PLAYING, pending = VOID_PENDING
GstElement(queue1), status = PLAYING, pending = VOID_PENDING
GstElement(nvvconv3), status = PLAYING, pending = VOID_PENDING
GstElement(myconv), status = PLAYING, pending = VOID_PENDING
GstElement(nvv4l2decoder1), status = PLAYING, pending = VOID_PENDING
GstElement(rtph265depay1), status = PLAYING, pending = VOID_PENDING
GstElement(rtspsrc1), status = PLAYING, pending = VOID_PENDING

then to go from pipline 2 to pipeline 1. the status it looks that it is working but the stream is frozen and the code goes unitl gst_bus_poll(bus, GST_MESSAGE_EOS, GST_CLOCK_TIME_NONE);

----- status pipeline1 ---
GstElement(capsfilter10), status = PLAYING, pending = VOID_PENDING
GstElement(capsfilter4), status = PLAYING, pending = VOID_PENDING
GstElement(capsfilter3), status = PLAYING, pending = VOID_PENDING
GstElement(capsfilter2), status = PLAYING, pending = VOID_PENDING
GstElement(capsfilter1), status = PLAYING, pending = VOID_PENDING
GstElement(udpsink0), status = PLAYING, pending = VOID_PENDING
GstElement(rtpvp9pay0), status = PLAYING, pending = VOID_PENDING
GstElement(nvv4l2vp9enc0), status = PLAYING, pending = VOID_PENDING
GstElement(queue0), status = PLAYING, pending = VOID_PENDING
GstElement(nvvconv1), status = PLAYING, pending = VOID_PENDING
GstElement(myconv), status = PLAYING, pending = VOID_PENDING
GstElement(nvv4l2decoder0), status = PLAYING, pending = VOID_PENDING
GstElement(rtph265depay0), status = PLAYING, pending = VOID_PENDING
GstElement(rtspsrc0), status = PLAYING, pending = VOID_PENDING
========================
----- status pipeline2 ---
GstElement(capsfilter11), status = PAUSED, pending = VOID_PENDING
GstElement(capsfilter9), status = PAUSED, pending = VOID_PENDING
GstElement(capsfilter8), status = PAUSED, pending = VOID_PENDING
GstElement(capsfilter7), status = PAUSED, pending = VOID_PENDING
GstElement(capsfilter6), status = PAUSED, pending = VOID_PENDING
GstElement(udpsink1), status = PAUSED, pending = VOID_PENDING
GstElement(rtpvp9pay1), status = PAUSED, pending = VOID_PENDING
GstElement(nvv4l2vp9enc1), status = PAUSED, pending = VOID_PENDING
GstElement(queue1), status = PAUSED, pending = VOID_PENDING
GstElement(nvvconv3), status = PAUSED, pending = VOID_PENDING
GstElement(myconv), status = PAUSED, pending = VOID_PENDING
GstElement(nvv4l2decoder1), status = PAUSED, pending = VOID_PENDING
GstElement(rtph265depay1), status = PAUSED, pending = VOID_PENDING
GstElement(rtspsrc1), status = PAUSED, pending = VOID_PENDING
========================

Another option i have tried is to set the pipelines to NULL and create again the pipeline but then i got the error:

“GStreamer-WARNING **: 19:09:21.163: Trying to join task 0x7f100243b0 from its thread would deadlock. You cannot change the state of an element from its streaming thread. Use g_idle_add() or post a GstMessage on the bus to schedule the state change from the main thread”

[DaneLLL]

Hi,
For live source you would need to send EoS in the application, please refer to this sample:
GStreamer C++ nvarguscamerasrc - #5 by DaneLLL

Would need to send EoS by calling:

gst_element_send_event ((GstElement*)gst_pipeline, gst_event_new_eos ());

And please switch to NULL state and re-initialize the pipeline.

[vcb1]

Hi,

I am trying to send EoS message and then afterwards switch to NULL. However, the problem is that i do not get the EoS message. The program is block in gst_bus_poll

The other option is to set the state to NULL:

gst_element_set_state((GstElement *)gst_pipeline, GST_STATE_NULL);

However this produces a warning:

“GStreamer-WARNING **: 19:09:21.163: Trying to join task 0x7f100243b0 from its thread would deadlock. You cannot change the state of an element from its streaming thread. Use g_idle_add() or post a GstMessage on the bus to schedule the state change from the main thread”

this results on a non–controlled behavior sometimes it works and i can change between pipelines and sometimes the image is frozen. How can avoid this warning? As i said i have tried to post a GstMessage on the bus but it is not sending the message.

[DaneLLL]

Hi,
You may try to apply the string to this python sample and check if it works:
Nvv4l2decoder sometimes fails to negotiate with downstream after several pipeline re-launches - #16 by DaneLLL

We have tired UDP and RTSP and don’t hit the issue. The RTSP string is like:

    pipeline = Gst.parse_launch(
        "rtspsrc location=rtsp://10.19.107.227:8554/test ! rtph264depay ! h264parse ! nvv4l2decoder ! nvvidconv ! video/x-raw,format=I420 ! fakesink "
    )