Streaming images using appsrc

[fgfernandez0321]

I have this example in python where I want to stream images via UDP. In this
case I'm testing using autovideosink in order to know how the images change.
Based on the documentation I need to free the buffer when it is used however
I haven't found a function on Python bindings to solve this. I tried to use
"push_buffer" function instead of signals but it is not exist at least in my
version. At this point, when the first images is shown, I can't push more
buffers because "enough-data" signal is emitted and "need-data" is not
emitted again in order to start push buffers.

Could you please help me to clarify me? Thank you  

class SenderImages:
    def __init__(self):
        # Control if it is allowed push buffer in queue using "need-data"
and "enough-data" signals
        self.is_push_buffer_allowed = None

        self._mainloop = GObject.MainLoop()
        auto_video_sink_pipeline = "appsrc name=source ! decodebin !
imagefreeze ! autovideosink"
        self._pipeline = Gst.parse_launch(auto_video_sink_pipeline)

        # udp_sink_pipeline = "appsrc name=source ! decodebin ! imagefreeze
! udpsink host=localhost port=55100"
        # self._pipeline = Gst.parse_launch(udp_sink_pipeline)

        self._src = self._pipeline.get_by_name('source')
        self._src.connect('need-data', self.start_feed)
        self._src.connect('enough-data', self.stop_feed)
        # length is just a hint and when it is set to -1, any number of
bytes can be pushed into appsrc
        # self._src.set_property("length", -1)

    def start_feed(self, src, length):
        print('======================> need data length: %s' % length)
        self.is_push_buffer_allowed = True

    def stop_feed(self, src):
        print('======================> enough_data')
        self.is_push_buffer_allowed = False

    def play(self):
        self._pipeline.set_state(Gst.State.PLAYING)

    def stop(self):
        self._pipeline.set_state(Gst.State.NULL)

    def run(self):
        """ Run - blocking. """
        self._mainloop.run()

    def push(self):
        """ Push a buffer into the source. """
        if self.is_push_buffer_allowed:
            image_number = randint(1, 4)
            filename = 'images/%s.jpg' % image_number

            img = PILImage.open(filename, mode='r')
            img_byte_array = io.BytesIO()
            img.save(img_byte_array, format='JPEG')
            img_byte_array = img_byte_array.getvalue()

            buffer = Gst.Buffer.new_wrapped(img_byte_array)
            # Push the buffer into the appsrc
            gst_flow_return = self._src.emit('push-buffer', buffer)
            # gst_flow_return = self._src.push_buffer(buffer)
           
            # Free the buffer now that we are done with it            
            # Do something            
            # Not function found to unref buffer

            if gst_flow_return != Gst.FlowReturn.OK:
                print('We got some error, stop sending data')

        else:
            print('It is enough data for buffer....')


gst_app_src = SenderImages()
gst_app_src.play()

index = 0
while index < 1000:
    print('========================= Showing picture...')
    gst_app_src.push()

    time.sleep(1)
    index += 1



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[Arjen Veenhuizen]

Couple of pointers:
1. you don't need to explicitly free the buffers when using Python.
2. Set the caps on your appsrc element: "image/jpeg,framerate=30/1"
3. Set 'format' = 'bytes' property and 'do-timestamp' = 'true' on appsrc
4. emit("push-sample", sample) is the way to go
5. add a queue between appsrc and decodebin.




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[fgfernandez0321]

Hi Arjen,

Thank you for your help. I followed your steps however not working as
expected. At the end, what I would like to achieve is to show the images
using autovideosink as video playing but using images instead of a video
with frames... I send you a zip with the source just in case you need it.
SenderImages.zip
<http://gstreamer-devel.966125.n4.nabble.com/file/t377167/SenderImages.zip>  

Regards

This the code based on your explanation:

from PIL import Image as PILImage
from random import randint
import time
import gi
import io

gi.require_version('Gst', '1.0')
gi.require_version('GstApp', '1.0')
gi.require_version('Gtk', '3.0')

# noinspection PyUnresolvedReferences
from gi.repository import GObject, Gst, Gtk

GObject.threads_init()
Gst.init(None)


class SenderImages:
    def __init__(self):
        # Control if it is allowed push buffer in queue using "need-data"
and "enough-data" signals
        self.is_push_buffer_allowed = None

        self._mainloop = GObject.MainLoop()
        auto_video_sink_pipeline = "appsrc name=source !
image/jpeg,framerate=30/1 ! queue ! decodebin ! imagefreeze ! autovideosink"
        self._pipeline = Gst.parse_launch(auto_video_sink_pipeline)

        self._src = self._pipeline.get_by_name('source')
        self._src.connect('need-data', self.start_feed)
        self._src.connect('enough-data', self.stop_feed)

        self._src.set_property('format', 'bytes')
        self._src.set_property('do-timestamp', 'true')  # GstBase.BaseSrc

    def start_feed(self, src, length):
        print('======================> need data length: %s' % length)
        self.is_push_buffer_allowed = True

    def stop_feed(self, src):
        print('======================> enough_data')
        self.is_push_buffer_allowed = False

    def play(self):
        self._pipeline.set_state(Gst.State.PLAYING)

    def stop(self):
        self._pipeline.set_state(Gst.State.NULL)

    def run(self):
        """ Run - blocking. """
        self._mainloop.run()

    def push(self):
        """ Push a buffer into the source. """
        if self.is_push_buffer_allowed:
            image_number = randint(1, 4)
            filename = 'images/%s.jpg' % image_number

            img = PILImage.open(filename, mode='r')
            img_byte_array = io.BytesIO()
            img.save(img_byte_array, format='JPEG')
            img_byte_array = img_byte_array.getvalue()

            buffer = Gst.Buffer.new_wrapped(img_byte_array)
            gst_sample = Gst.Sample.new(buffer)
            gst_flow_return = self._src.emit('push-sample', gst_sample)

            if gst_flow_return != Gst.FlowReturn.OK:
                print('We got some error, stop sending data')

        else:
            print('It is enough data for buffer....')


sender = SenderImages()
sender.play()

index = 0
while index < 1000:
    print('========================= Showing picture...')
    sender.push()

    time.sleep(1)
    index += 1




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[Arjen Veenhuizen]

This should get you going:
https://gist.github.com/arjenveenhuizen/00959940296e03c40fb9cf0087f6116d



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[fgfernandez0321]

Hi Arjen,

It is working. Thank you



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