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Ahmed Hussein
Ahmed Hussein

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Part 0: Helloworld Gstreamer

#gstreamer #linux #ubuntu

In this series, we will have a beginner-friendly introduction to the world of GStreamer.

GStreamer is a powerful open-source multimedia framework used to build streaming media applications. It allows developers to create pipelines that process, transform, and transmit audio, video, and other multimedia data.

My primary focus throughout this series will be video processing. Since GStreamer is built on top of GLib, I will also highlight the differences between GStreamer APIs and GLib APIs whenever they appear. Understanding this distinction early will help avoid confusion when reading examples and documentation.

What We Will Learn

In this article, we will cover:

  • How to install GStreamer.
  • How to verify that GStreamer is working correctly.
  • How to use gst-launch-1.0.
  • How to display a simple video using a GStreamer pipeline.

1. Install GStreamer

Before writing any code, we need to install GStreamer and its plugins.

Ubuntu 

sudo apt update

sudo apt install \
    gstreamer1.0-tools \
    gstreamer1.0-plugins-base \
    gstreamer1.0-plugins-good
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This installs:

Package Description
gstreamer1.0-tools Command-line tools such as gst-launch-1.0
plugins-base Core plugins used by most applications
plugins-good High-quality plugins maintained by the GStreamer project
plugins-bad Experimental or less mature plugins You can skip it
plugins-ugly Plugins with licensing restrictions You can skip it

2. Validate GStreamer Installation

The simplest way to verify the installation is to check the version.

gst-launch-1.0 --version
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Example output: (Ubuntu 26.04)

gst-launch-1.0 version 1.28.2
GStreamer 1.28.2
https://launchpad.net/ubuntu/+source/gstreamer1.0
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If you see a version number, GStreamer is installed correctly.

You can also inspect a plugin using:

gst-inspect-1.0 videotestsrc
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This command displays information about the videotestsrc element.

An element is a building block in a GStreamer pipeline.

Examples:

  • Video source
  • Video decoder
  • Video encoder
  • Video sink
  • Network source

We will discuss elements in detail in future articles.

3. Display a Simple Video

One of the most useful tools for learning GStreamer is gst-launch-1.0.

It allows us to create and execute pipelines directly from the command line without writing any code.

Let's display a test pattern:

gst-launch-1.0 videotestsrc ! autovideosink
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You should see a window containing moving color bars.

The pipeline consists of two elements:

videotestsrc -> autovideosink
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Where:

  • videotestsrc generates test video frames.
  • autovideosink automatically selects an appropriate video output device.

The ! character connects two elements together. It is like bash pipe.

A GStreamer pipeline is essentially a graph of connected elements.

+--------------+      +---------------+
| videotestsrc | ---> | autovideosink |
+--------------+      +---------------+
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The data flows from left to right.

Running Forever

By default, videotestsrc generates frames continuously.

Press:

Ctrl+C
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to stop the pipeline.

Understanding What Happened

Even though this pipeline is extremely simple, it demonstrates the core GStreamer architecture:

  1. A source generates data.
  2. Data flows through a pipeline.
  3. A sink consumes the data.

Most real-world pipelines follow the same pattern.

Source -> Processing -> Sink
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For example:

Camera -> Decoder -> AI Inference -> Display
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or

File -> Decoder -> Encoder -> Network Stream
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As the series progresses, we will gradually replace simple elements with more advanced components.

4. Exercise

Try the following commands and observe the differences.

Display a different test pattern:

gst-launch-1.0 videotestsrc pattern=ball ! autovideosink
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Display only 100 buffers:

gst-launch-1.0 videotestsrc num-buffers=100 ! autovideosink
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Display detailed debugging information:

GST_DEBUG=2 gst-launch-1.0 videotestsrc ! autovideosink
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Questions:

  1. What happens when num-buffers=100 is used?
  2. How many patterns are available in videotestsrc?
  3. What additional information appears when GST_DEBUG=2 is enabled?

Summary

In this article, we learned:

  • What GStreamer is.
  • How to install it.
  • How to verify the installation.
  • How to use gst-launch-1.0.
  • How to create and run the simplest possible video pipeline.
  • You can find the post in my personal blog

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