May 12, 2019

How to implement Object Detection in Video with Gstreamer in Python using Tensorflow?

By taras.lishchenko Deep Learning, Gstreamer, Tensorflow, Tutorials 0 Comments

In this tutorial we are going to implement Object Detection plugin for Gstreamer using pre-trained models from Tensorflow Models Zoo and inject it into Video Streaming Pipeline.

Time to read: 20 min
Code
Libraries: OpenCV, Gstreamer, Numpy, Tensorflow
Plugins: videotestsrc, videoconvert, fakesink, filesrc, fpsdisplaysink, decodebin, gtksink, autovideosink, capsfilter, souphttpsrc
Goal: Create Gstreamer Plugin that detects objects in each Video Frame using Tensorflow Models Zoo

In previous posts we’ve already learnt How to create simple Gstreamer Plugin in Python and implemented simple Blur Filter as Gstreamer Plugin using OpenCV . Now let’s make a step forward.

Requirements

OS: Ubuntu 16,18 LTS
Python 3
Install Gstreamer (latest version). Use guide “How to install Gstreamer from sources“

How it works?

Setup Environment

Download video (ex: video.mp4) (Note: check additional section to use get stream from raw Youtube link)
Check simple Gstreamer pipeline works with downloaded video well

gst-launch-1.0 filesrc location=video.mp4 ! decodebin ! videoconvert ! video/x-raw,format=RGB ! videoconvert ! gtksink sync=False

1	gst-launch-1.0 filesrc location=video.mp4 ! decodebin ! videoconvert ! video/x-raw,format=RGB ! videoconvert ! gtksink sync=False

Note: video/x-raw,format=RGB (capsfilter plugin). Converts output format from previous plugin to input format of next plugin.

Download and Extract ANY model from Tensorflow Models Zoo (example: ssdlite_mobilenet_v2_coco).
Get code

git clone https://github.com/jackersson/gst-plugins-tf.git

1	git clone https://github.com/jackersson/gst-plugins-tf.git

3. Setup Environment using commands

Note:

Install Tensorflow (CPU or GPU version)

pip install tensorflow # For CPU version pip install tensorflow-gpu # For GPU version

1
2

pip install tensorflow # For CPU version
pip install tensorflow-gpu # For GPU version

Install Gstreamer (latest version). Use guide “How to install Gstreamer from sources”
- Make sure gst-python is installed (to enable Python support for Gstreamer Plugins)

Note: Install gst-python . Highly recommended to use guide from “How to install Gstreamer from sources” (Gst-Python Section). And before going to next part check that test case is working and no error being printed

wget https://bit.ly/2Eg4b8s python3 gstreamer_empty_plugin_test_case.py

1
2

wget https://bit.ly/2Eg4b8s
python3 gstreamer_empty_plugin_test_case.py

Run

1. Edit config (format explained)

weights: "ssdlite_mobilenet_v2_coco/frozen_inference_graph.pb"  # path to model
threshold: 0.4 
per_process_gpu_memory_fraction: 0.0
device: "/device:GPU:0"
labels: "<a href="https://github.com/jackersson/gst-plugins-tf/blob/master/data/mscoco_label_map.yml">data/mscoco_label_map.yml</a>"
input_shape: [300, 300]
log_device_placemenent: falsewget https://bit.ly/2Eg4b8s
python3 gstreamer_empty_plugin_test_case.py

weights: "ssdlite_mobilenet_v2_coco/frozen_inference_graph.pb" # path to model

threshold: 0.4

per_process_gpu_memory_fraction: 0.0

device: "/device:GPU:0"

labels: "<a href="https://github.com/jackersson/gst-plugins-tf/blob/master/data/mscoco_label_map.yml">data/mscoco_label_map.yml</a>"

input_shape: [300, 300]

log_device_placemenent: falsewget https://bit.ly/2Eg4b8s

python3 gstreamer_empty_plugin_test_case.py

2. Launch (with print to console)

cd gst-plugins-tf
export GST_PLUGIN_PATH=$PWD/gst

GST_DEBUG=python:4 gst-launch-1.0 filesrc location=<a href="https://www.youtube.com/watch?v=xjDjIWPwcPU">video.mp4</a> ! decodebin ! videoconvert ! \
video/x-raw,format=RGB ! gst_tf_detection config=<a href="https://github.com/jackersson/gst-plugins-tf/blob/master/data/tf_object_api_cfg.yml">data/tf_object_api_cfg.yml</a> ! videoconvert ! gtksink sync=False

cd gst-plugins-tf

export GST_PLUGIN_PATH=$PWD/gst

GST_DEBUG=python:4 gst-launch-1.0 filesrc location=<a href="https://www.youtube.com/watch?v=xjDjIWPwcPU">video.mp4</a> ! decodebin ! videoconvert ! \

video/x-raw,format=RGB ! gst_tf_detection config=<a href="https://github.com/jackersson/gst-plugins-tf/blob/master/data/tf_object_api_cfg.yml">data/tf_object_api_cfg.yml</a> ! videoconvert ! gtksink sync=False

Note: <GST_DEBUG=python:4> enables printing logs to console when launching pipeline (gstreamer debugging tools).

In Terminal you should see something like this:

Note: App should print something like this (list of dicts with object’s class_name, confidence, bounding_box):

[{'confidence': 0.6499642729759216, 'bounding_box': [402, 112, 300, 429], 'class_name': 'giraffe'}, \ {'confidence': 0.4659585952758789, 'bounding_box': [761, 544, 67, 79], 'class_name': 'person'}]

1
2

[{'confidence': 0.6499642729759216, 'bounding_box': [402, 112, 300, 429], 'class_name': 'giraffe'}, \
{'confidence': 0.4659585952758789, 'bounding_box': [761, 544, 67, 79], 'class_name': 'person'}]

3. Launch (with object’s bounding boxes over video)

gst-launch-1.0 filesrc location=video.mp4 ! decodebin ! videoconvert ! video/x-raw,format=RGB ! \
gst_tf_detection config=data/tf_object_api_cfg.yml ! videoconvert ! gst_detection_overlay ! videoconvert ! gtksink sync=False

1 2	gst-launch-1.0 filesrc location=video.mp4 ! decodebin ! videoconvert ! video/x-raw,format=RGB ! \ gst_tf_detection config=data/tf_object_api_cfg.yml ! videoconvert ! gst_detection_overlay ! videoconvert ! gtksink sync=False

Note: Look at gst_detection_overlay to check how drawing functions implemented

Explanation

The steps to create such a plugin a heavily built on top of this tutorial .

Let’s dive.

Define buffer format for SRC/SINK of plugin. Since Tensorflow Object Detection models works mostly with RGB define next templates (pay attention to video/x-raw,format={RGB}):

_srctemplate = Gst.PadTemplate.new('src', Gst.PadDirection.SRC,
                                   Gst.PadPresence.ALWAYS,
                                   Gst.Caps.from_string("video/x-raw,format={RGB}"))
_sinktemplate = Gst.PadTemplate.new('sink', Gst.PadDirection.SINK,
                                    Gst.PadPresence.ALWAYS,
                                    Gst.Caps.from_string("video/x-raw,format={RGB}"))

_srctemplate = Gst.PadTemplate.new('src', Gst.PadDirection.SRC,

Gst.PadPresence.ALWAYS,

Gst.Caps.from_string("video/x-raw,format={RGB}"))

_sinktemplate = Gst.PadTemplate.new('sink', Gst.PadDirection.SINK,

Gst.PadPresence.ALWAYS,

Gst.Caps.from_string("video/x-raw,format={RGB}"))

2. Define properties for simple arguments passing to gstreamer plugin.

First, you have noticed that plugin has “config” property. Config’s file format is described here (YAML). In general the main purpose of this config is to pass parameters to our Tensorflow Model (ex.: confidence threshold, model’s weights path, device to place graph, labels, etc.)

gst_tf_detection config=tf_object_api_cfg.yml

1	gst_tf_detection config=tf_object_api_cfg.yml

Note: Labels is also just a file with next format (YAML): <class_id: class_name>. For example:

1: person 2: bicycle 3: car 4: motorcycle ... 90:toothbrush

1
2
3
4
5
6

1: person
2: bicycle
3: car
4: motorcycle
...
90:toothbrush

Also config file for Gstreamer Plugin is the common practice to pass more than 3 parameters, as it much easier to reuse and extend in future. For example, look at DeepStream SDK plugins.

To allow Gstreamer Plugin get/set properties define next:

__gproperties__ = {
    "model": (GObject.TYPE_PYOBJECT,
              "model",
              "Contains model TfObjectDetectionModel",
              GObject.ParamFlags.READWRITE),

    "config": (str,
              "Path to config file",
              "Contains path to config *.yml supported by TfObjectDetectionModel",
               None,  # default
               GObject.ParamFlags.READWRITE),
}

__gproperties__ = {

"model": (GObject.TYPE_PYOBJECT,

"model",

"Contains model TfObjectDetectionModel",

GObject.ParamFlags.READWRITE),

"config": (str,

"Path to config file",

"Contains path to config *.yml supported by TfObjectDetectionModel",

None, # default

GObject.ParamFlags.READWRITE),

}

Note: Property “model” is used to pass existing model to plugin, without creating it. It could be useful if you want just to share single model without creating multiple instances.

3. Implement chainfunc() with Tensorflow model Inference. So the main steps are: Convert Gst.Buffer to np,ndarray, perform inference of image, write objects to Gst.Buffer as metadata (recap: How to add metadata to gstreamer buffer). Check the following code:

 def chainfunc(self, pad: Gst.Pad, parent, buffer: Gst.Buffer) -&gt; Gst.FlowReturn:
        """
        :param parent: GstDetectionOverlay
        """
        if self.model is None:
            return self.srcpad.push(buffer)

        try:
            # Convert Gst.Buffer to np.ndarray
            image = gst_buffer_with_pad_to_ndarray(buffer, pad, self._channels)

            # model inference
            objects = self.model.process_single(image)
            Gst.info(str(objects))

            # write objects to as Gst.Buffer's metadata
            # Explained: http://lifestyletransfer.com/how-to-add-metadata-to-gstreamer-buffer-in-python/
            gst_meta_write(buffer, objects)
        except Exception as e:
            logging.error(e)
            traceback.print_exc()
            return Gst.FlowReturn.ERROR

        return self.srcpad.push(buffer)

def chainfunc(self, pad: Gst.Pad, parent, buffer: Gst.Buffer) -> Gst.FlowReturn:

"""

:param parent: GstDetectionOverlay

"""

if self.model is None:

return self.srcpad.push(buffer)

try:

# Convert Gst.Buffer to np.ndarray

image = gst_buffer_with_pad_to_ndarray(buffer, pad, self._channels)

# model inference

objects = self.model.process_single(image)

Gst.info(str(objects))

# write objects to as Gst.Buffer's metadata

# Explained: http://lifestyletransfer.com/how-to-add-metadata-to-gstreamer-buffer-in-python/

gst_meta_write(buffer, objects)

except Exception as e:

logging.error(e)

traceback.print_exc()

return Gst.FlowReturn.ERROR

return self.srcpad.push(buffer)

We won’t deep dive much into implementation on how to load Tensorflow model. Just have a look at code here. (If there any questions on those lines of code, leave a comment)

Additional

# Gstreamer + Youtube

To run Gstreamer pipeline from Youtube link (without downloading the video file) we are going to use youtube-dl library. First install dependencies:\

source venv/bin/activate
pip install youtube-dl

1 2	source venv/bin/activate pip install youtube-dl

And let’s edit command from previous examples link described in here (gstreamer commands cheatsheet)

gst-launch-1.0 souphttpsrc is-live=true location="$(youtube-dl --format mp4 -get-url https://www.youtube.com/watch?v=xjDjIWPwcPU)" ! \ 
decodebin ! videoconvert ! video/x-raw,format=RGB ! gst_tf_detection config=data/tf_object_api_cfg.yml \
! videoconvert ! gst_detection_overlay ! videoconvert ! gtksink sync=false

gst-launch-1.0 souphttpsrc is-live=true location="$(youtube-dl --format mp4 -get-url https://www.youtube.com/watch?v=xjDjIWPwcPU)" ! \

decodebin ! videoconvert ! video/x-raw,format=RGB ! gst_tf_detection config=data/tf_object_api_cfg.yml \

! videoconvert ! gst_detection_overlay ! videoconvert ! gtksink sync=false

Note: Next command prints link (https) to Youtube Video with specified format (mp4)

youtube-dl --format mp4 --get-url <youtube_link>

1

youtube-dl --format mp4 --get-url <youtube_link>

And souphttpsrc is a plugin that allows to read buffers from http stream specified by url

Hope everything works as expected 😉 In case of troubles with running code leave comments or open an issue on Github.

Tags:deep learning, gstreamer, gstreamer pipeline, gstreamer plugin, gstreamer python, object detection, tensorflow, video streaming, youtube

LifeStyleTransfer

How to implement Object Detection in Video with Gstreamer in Python using Tensorflow?

Requirements

How it works?

Setup Environment

Explanation

Additional

# Gstreamer + Youtube

About Author

taras.lishchenko

Add a Comment

Requirements

How it works?

Setup Environment

Explanation

Additional

# Gstreamer + Youtube

Related Posts

About Author

taras.lishchenko

Add a Comment