dynamically add uridecodebin to compositor

Question

I am trying to dynamically add another uridecodebin to compositor/audiomixer

this is my "starting" pipeline, it works:

    compositor name=videomix !  tee name=vo 
    audiomixer name=audiomix async=true !   tee name=au



    hlssink2  async-handling=true name=output location=out/hlssink.%05d.ts playlist-location=out/out.m3u8  sync=true target-duration=10 playlist-length=5 max-files=5 name=hls 
    vo. 
            ! queue ! videoconvert ! videoscale ! videorate
            !   x264enc cabac=false  key-int-max=50 quantizer=0  pass=0 speed-preset=ultrafast  tune=zerolatency bitrate=8000   byte-stream=true ! video/x-h264,width=1920,height=1080,pixel-aspect-ratio=1/1,framerate=25/1,format=RGBA,profile=constrained-baseline ! hls.video
    au. 
            ! audioconvert
            ! audiorate
            ! audioresample
            ! audio/x-raw, rate=44100, layout=interleaved, format=F32LE, channels=2 ! avenc_aac bitrate=128000 ac=2
            ! audio/mpeg
            ! hls.audio


    uridecodebin connection-speed=50000000  uri=https://HLS1        sync=false async=true name=d1 
        d1. ! videoconvert ! videoscale ! video/x-raw,width=1920,height=1080 ! videomix.
        d1. ! audioconvert
            ! audiorate
            ! audioresample
            ! volume volume=1.0
            ! audiomix.
    
    

    uridecodebin connection-speed=50000000  uri="https://HLS2"      sync=false async=true name=d2
        d2. ! videoconvert ! videoscale ! video/x-raw,width=1920,height=1080 ! videomix.
        d2. ! audioconvert
            ! audiorate
            ! audioresample
            ! volume volume=1.0
            ! audiomix.
    

I need the tee - because in final production I want to produce a hls output and another one.

I try to add another set of uridecodebin

to the running pipeline - using go-gst (but I think my problem is a basic understanding, so any solution in any language would be fine - porting should not be the problem)

bin := gst.NewBin("dyn1")

// uridecodebin connection-speed=50000000  uri="https://HLS3"       sync=false async=true name=d2
// d2. ! videoconvert ! videoscale ! video/x-raw,width=1920,height=1080 ! videomix.
// d2. ! audioconvert
//  ! audiorate
//  ! audioresample
//  ! volume volume=1.0
//  ! audiomix.

els, _ := gst.NewElementMany("uridecodebin", "videoconvert", "videoscale", "audioconvert", "audiorate", "audioresample", "volume")

uridecodebin := els[0]
uridecodebin.Set("name", "dynamic1")
uridecodebin.Set("uri", "https://HLSDYNAMICADDED")
uridecodebin.Set("sync", false)
uridecodebin.Set("async", true)

videoconvert := els[1]
videoscale := els[2]
audioconvert := els[3]
audiorate := els[4]
audioresample := els[5]
volume := els[6]

gst.ElementLinkMany(uridecodebin, videoconvert, videoscale)
gst.ElementLinkMany(uridecodebin, audioconvert, audiorate, audioresample, volume)

bin.AddMany(uridecodebin, videoconvert, videoscale, audioconvert, audiorate, audioresample, volume)

videomixer, _ := pipeline.GetElementByName("videomix")
audiomixer, _ := pipeline.GetElementByName("audiomix")

pipeline.Add(bin.Element)

volume.Link(audiomixer)
videoscale.LinkFiltered(videomixer, gst.NewCapsFromString("video/x-raw,width=1920,height=1080"))
bin.SetState(gst.StatePaused)

when I run the pipeline it works, and with a couple of seconds delay, the "ADDING" happens, and the pipeline crashes with:

    ERROR: Internal data stream error.
    DEBUG: ../gst-libs/gst/adaptivedemux/gstadaptivedemux.c(3891): 
    gst_adaptive_demux_stream_download_loop (): 
/GstPipeline:pipeline0/GstBin:dyn1/GstURIDecodeBin:dynamic1/GstDecodeBin:decodebin3/GstHLSDemux:hlsdemux3:
streaming stopped, reason not-linked (-1)

Answer 1

Check error return values from your functions.

gst.ElementLinkMany(uridecodebin, ...) is going to fail in your code: uridecodebin adds pads dynamically, you need to link from the pad-added signal.

See e.g. here and here for more details about that in the GStreamer documentation.