udp使用python在gstreamer中播放视频

Question

All this is done in the same computer. I would like to receive a video stream from Gstreamer using the GST using python . First I will introduce gstreamer pipeline

gst-launch-1.0 v4l2src !  video/x-raw,width=640,height=480 !  timeoverlay !  tee name="local" !  queue !  autovideosink local. !  queue ! jpegenc! rtpjpegpay !  udpsink host=127.0.0.1 port= 5000

then I want to get a video stream from gstreamer with a script in python to output in opencv

import sys
from gi.repository import Gst
import cv2
import numpy

Gst.init(None)


image_arr = None

def gst_to_opencv(sample):
    buf = sample.get_buffer()
    caps = sample.get_caps()
    print caps.get_structure(0).get_value('format')
    print caps.get_structure(0).get_value('height')
    print caps.get_structure(0).get_value('width')

    print buf.get_size()

    arr = numpy.ndarray(
        (caps.get_structure(0).get_value('height'),
         caps.get_structure(0).get_value('width'),
         3),
        buffer=buf.extract_dup(0, buf.get_size()),
        dtype=numpy.uint8)
    return arr

def new_buffer(sink, data):
    global image_arr
    sample = sink.emit("pull-sample")
    buf = sample.get_buffer()
    print "Timestamp: ", buf.pts
    arr = gst_to_opencv(sample)
    image_arr = arr
    return Gst.FlowReturn.OK

# Create the elements
source = Gst.ElementFactory.make("udpsrc", None)
depay = Gst.ElementFactory.make("rtpjpegdepay", None)
decoder = Gst.ElementFactory.make("jpegdec", None)
sink = Gst.ElementFactory.make("appsink", None)



# Create the empty pipeline111
pipeline = Gst.Pipeline.new("test-pipeline")

if not pipeline:
    print("Not all elements could be created.")
    exit(-1)


sink.set_property("emit-signals", True)
#sink.set_property("max-buffers", 2)
# # sink.set_property("drop", True)
# # sink.set_property("sync", False)

#caps = Gst.caps_from_string("application/x-rtp, encoding name=JPEG, payload=26, width=640, height=480; video/x-bayer,format=(string){rggb,bggr,grbg,gbrg}")
caps = Gst.caps_from_string(" application/x-rtp, encoding-name=JPEG, payload=26, format=(string)[]{rggb,bggr,grbg,gbrg}")
sink.set_property("caps", caps)


sink.connect("new-sample", new_buffer, sink)

# Build the pipeline
pipeline.add(source)
pipeline.add(depay)
pipeline.add(decoder)
pipeline.add(sink)
if not Gst.Element.link(source, depay):
    print("Elements could not be linked.")
    exit(-1)
if not Gst.Element.link(depay, decoder):
    print("Elements could not be linked.")
    exit(-1)
if not Gst.Element.link(decoder, sink):
    print("Elements could not be linked.")
    exit(-1)

# Modify the source's properties
source.set_property("port", 5000)

# Start playing
ret = pipeline.set_state(Gst.State.PLAYING)
if ret == Gst.StateChangeReturn.FAILURE:
    print("Unable to set the pipeline to the playing state.")
    exit(-1)

# Wait until error or EOS
bus = pipeline.get_bus()


# Parse message
while True:
    message = bus.timed_pop_filtered(10000, Gst.MessageType.ANY)
    # print "image_arr: ", image_arr
    if image_arr is not None:   
        cv2.imshow("appsink image arr", image_arr)
        cv2.waitKey(1)
    if message:
        if message.type == Gst.MessageType.ERROR:
            err, debug = message.parse_error()
            print("Error received from element %s: %s" % (
                message.src.get_name(), err))
            print("Debugging information: %s" % debug)
            break
        elif message.type == Gst.MessageType.EOS:
            print("End-Of-Stream reached.")
            break
        elif message.type == Gst.MessageType.STATE_CHANGED:
            if isinstance(message.src, Gst.Pipeline):
                old_state, new_state, pending_state = message.parse_state_changed()
                print("Pipeline state changed from %s to %s." %
                       (old_state.value_nick, new_state.value_nick))
        else:
            print("Unexpected message received.")

# Free resources
pipeline.set_state(Gst.State.NULL)

I see this error

Pipeline state changed from null to ready.
Unexpected message received.
Pipeline state changed from ready to paused.
Unexpected message received.
Unexpected message received.
Unexpected message received.
Error received from element rtpjpegdepay0: No RTP format was negotiated.
Debugging information: gstrtpbasedepayload.c(373): gst_rtp_base_depayload_chain (): /GstPipeline:test-pipeline/GstRtpJPEGDepay:rtpjpegdepay0:
Input buffers need to have RTP caps set on them. This is usually achieved by setting the 'caps' property of the upstream source element (often udpsrc or appsrc), or by putting a capsfilter element before the depayloader and setting the 'caps' property on that. Also see http://cgit.freedesktop.org/gstreamer/gst-plugins-good/tree/gst/rtp/README

How to fix it?

receiver gstreamer pipeline

gst-launch-1.0 udpsrc port=5000 !  application/x-rtp, encoding-name=JPEG,payload=26 !  rtpjpegdepay ! jpegdec ! autovideosink 

Answer 1

You have to negotiate caps on udpsrc like

gst-launch-1.0 udpsrc port=9090 caps=application/x-rtp,media=video,encoding-name=MP2T 

How you are sending the data, based on that these caps will vary. You have to negotiate RTP Format, as you have used an rtp pay element before udpsink.