Write image frames into gstreamer rtp pipeline

Question

I am trying to use the gstreamer pipeline to view an rtp stream in vlc on my computer. I mostly looked into this thread. My end result is something like this

#!/usr/bin/env python

import gi
import numpy as np

gi.require_version('Gst', '1.0')
from gi.repository import Gst, GObject
import time


class RtpPipeline(object):
    def __init__(self):
        self.number_frames = 0
        self.fps = 30
        self.duration = 1 / self.fps * Gst.SECOND  # duration of a frame in nanoseconds
        self.launch_string = 'appsrc name=source ' \
                             '!videoconvert !x264enc speed-preset=ultrafast tune=zerolatency byte-stream=true ' \
                             '! mpegtsmux ! rtpmp2tpay ! udpsink host=127.0.0.1 port=5000'
        pipeline = Gst.parse_launch(self.launch_string)
        appsrc = pipeline.get_child_by_name('source')

        while True:
            try:
                img = np.zeros([320, 320, 3], dtype=np.uint8)
                img.fill(255)  # white image
                data = img.tostring()
                buf = Gst.Buffer.new_allocate(None, len(data), None)
                buf.fill(0, data)
                buf.duration = self.duration
                timestamp = self.number_frames * self.duration
                buf.pts = buf.dts = int(timestamp)
                buf.offset = timestamp
                self.number_frames += 1
                retval = appsrc.emit('push-buffer', buf)
                if retval != Gst.FlowReturn.OK:
                    print(retval)
                time.sleep(0.2)
            except Exception as e:
                break


Gst.init(None)

factory = RtpPipeline()

loop = GObject.MainLoop()
loop.run()

Which doesn't throw an error but does not show anything in my vlc client. Any tips would be great (OpenCV VideoWriter is not an option).

Answer 1

I think the most important thing that was missing was:

pipeline.set_state(Gst.State.PLAYING)

I also added the comments from mail2subhajit. Here is the final result, which is kinda buggy but is a good start.

class RtpPipeline(object):
    def __init__(self):
        self.number_frames = 0
        self.fps = 30
        self.cap = cv2.VideoCapture(0)
        self.duration = 1 / self.fps * Gst.SECOND  # duration of a frame in nanoseconds
        self.launch_string = 'appsrc name=source is-live=true format=GST_FORMAT_TIME ' \
                             ' caps=video/x-raw,format=BGR,width=640,height=480,framerate=30/1 ' \
                             '! videoconvert ! video/x-raw,format=I420 ' \
                             '! x264enc speed-preset=ultrafast tune=zerolatency byte-stream=true ' \
                             '! mpegtsmux ! rtpmp2tpay ! udpsink host=127.0.0.1 port=5000 sync=false'
        pipeline = Gst.parse_launch(self.launch_string)
        appsrc = pipeline.get_child_by_name('source')
        pipeline.set_state(Gst.State.PLAYING)

        while True:
            try:
                ret, frame = self.cap.read()
                start = time.time()
                data = frame.tostring()
                buf = Gst.Buffer.new_allocate(None, len(data), None)
                buf.fill(0, data)
                buf.duration = self.duration
                timestamp = self.number_frames * self.duration
                buf.pts = buf.dts = int(timestamp)
                buf.offset = timestamp
                self.number_frames += 1
                retval = appsrc.emit('push-buffer', buf)
                if retval != Gst.FlowReturn.OK:
                    print(retval)
            except Exception as e:
                break