Snapshot

• Summary
  • Features
  • Limitations
• Installation
  • Stand-alone tarball
  • From source
  • Raspberry Pi OS
• Usage
  • List the available cameras
  • Display a video
  • Record a video stream
  • Using the configuration file
  • Set the logging level
• Development
  • Test
  • Tarball
  • Debugging
• License
• Troubleshooting
• Contributing
• FAQ

Summary

Snapshot is an application that allows you to view a video and record it as a set of snapshots. This is useful when you want to make a time-lapse of a video. The application has a graphical user interface to view the video and a command line interface to configure the application. It can also be configured using a configuration file. The project is written in C++ and uses Qt6. For more information, run snapshot --help, or continue reading.

Features

In short, snapshot contains the following features:

• List the available cameras.
• Display a video stream:
  • using RTSP, UDP or HTTP.
  • from a file.
  • from a (built-in) camera.
• Record a video in a set of snapshots at a given interval and duration.
• Configure the application using a configuration file.
• Has a command line interface.
• Runs on linux (including raspberry pi).

Limitations

• 64 bit Linux systems only
• glibc $\geq$ 2.35 (when using the tarball)
• X11, Wayland are supported. EGLFS is support is added, but not tested.
• Tested on Ubuntu 22.04, Arch linux and Raspberry Pi OS (bullseye).

Installation

The following sections explain how to install the project. You have two options: using the pre-built binaries. The easiest way is to use the pre-built binaries, i.e., the stand-alone tarball.

Stand-alone tarball

Requires that glibc $\geq$ 2.35

This is the easiest way to install the application.

Go to the releases page and download the latest tar.gz file. Extract the file using the following command:

tar -xvf snapshot-<version>-Linux.tar.gz

This creates a snapshot-<version> directory with the following structure:

snapshot-<version>
  ├── runtime/
  └── snapshot

the runtime directory contains files you should not touch. The snapshot script is the one that you should use to interact with the application. For example:

./snapshot-<version>/snapshot --help

will print the help message. For convenience, you can place the snapshot-<version> folder anywhere you like, and create a symlink to the snapshot script in a directory that is in your PATH. For example:

ln -s /path/to/snapshot-<version>/snapshot $HOME/bin/snapshot

here it is assumed that the $HOME/bin directory is in your PATH.

Extra information about the tarball is provided in Development.

From source

In this section, the steps to build the project from source are explained. In short:

• You can use the setup script to install the dependencies.
• A static or shared Qt build can be selected.
• A Qt account is needed in order to use the setup script.
• Using the configure script, the build can be configured.

Dependencies

Snapshot relies on the following dependencies:

Dependency	Version
Qt6: base & multimedia	6.6
ffmpeg	6.0, 6.1
boost	$\geq$ 1.74
spdlog	$\geq$ 1.9

Here, the Qt6 version is fixed. Other versions of ffmpeg, boost, and spdlog might work, but are not tested.

For building the project, the following dependencies are required:

• git
• CMake
• Ninja

Building the project was tested using $\text{clang}\geq 14$ and $\text{gcc}\geq 11$

cxxopts and googletest are also dependencies, but they are included in the project. The former as a header file in the 3rdparty directory, and the latter is installed using cmake.

Installing dependencies

The setup script only supports Arch Linux and Ubuntu 22.04. If you are using a different distribution, you need to install the dependencies yourself.

The following sections explain how to set up the environment for building the project. Since you need a specific version of Qt6, it is recommended to use the online installer of Qt which is included in this project.

Using the local installer is recommended as it installs the correct version in a subdirectory of the project. This way, the system Qt version is not affected.

Do the following:

• Clone the project:

  git clone https://github.com/BartSte/snapshot

  and cd into root directly the project (containing the .git directory).

• Register a Qt account on the website of Qt.

• Run the login-qt script with your credentials:

  ./scripts/login-qt --pw <password> --email <email>

  This creates a qtaccount.ini file at ~/.local/share/Qt which is used when downloading Qt.

• Run the setup script to install the dependencies:

  ./scripts/setup

  You can pass the --static (default) or --shared option to the script, to build Qt as a static or shared library. The --static option results in a longer build time, when compared do --shared, as Qt and ffmpeg are built from source. The --shared option results in a less build time as pre built Qt and ffmpeg libraries are used. However, the --shared option results in more libraries (*.so files) that need to be installed on your system.

  Once, the script is done, you can find the Qt libraries in the 3rdparty/Qt directory (ffmpeg is included). If you choose the --shared option, you can also find the ffmpeg libraries in the 3rdparty/ffmpeg directory.

Configure the build

Ensure that the root of the project is your current work directory. Run the configure script to configure the build:

./scripts/configure

This script creates a build directory containing the ninja build files. You can pass -- -DDBUILD_TESTING=ON to the script to enable the tests. Here, all arguments after the -- are passed to cmake directly.

Build

Build the project by running the following command:

cmake --build ./build

This creates the snapshot executable in the build/bin directory.

Install

Install the project by running the following command:

sudo cmake --install ./build

This will install the project in the /opt/snapshot directory. The /opt directory is chosen as snapshot is a self-contained application. The installed files tree is as follows:

/opt/snapshot
 ├── runtime/
 │   └── libs, bins, and qt plugins
 └── snapshot

Where snapshot is the entry point of the application. If you want to add the snapshot executable to your PATH, you can create a symlink to /usr/local/bin:

sudo ln -s /opt/snapshot/snapshot /usr/local/bin/snapshot

Or you can add the /opt/snapshot directory to your PATH.

If you have no root access, you can install the project in you home directory by using the --prefix option. For example, if you want to install the project in the $HOME/opt/snapshot directory, you can run the following:

cmake --install ./build --prefix $HOME/opt/snapshot

This will install the project in the $HOME/opt/snapshot directory, instead of the /opt/snapshot directory.

Raspberry Pi OS

• TODO

Usage

The snapshot executable should be executed from the command line. The following sections explain how to use the application. You can also run snapshot --help to get more information.

List the available cameras

By running the following command, a list of available cameras is shown:

snapshot --list

this outputs something like:

Index | Name                    | ID          | Is Default |
0     | HP TrueVision HD Camera | /dev/video0 | true       |

which means that there is one camera available, with index 0, name HP TrueVision HD Camera, id /dev/video0 and is the default camera.

Display a video

If we want to display a video stream from the default camera, we can run the following command:

snapshot --gui

If a camera is found, it will opens a window with the video stream from the default camera. You can also specify the camera to use. By doing:

snapshot --gui --camera "HP TrueVision HD Camera"

This will display the video stream from the camera with the name that matches the name given by the --list command in the previous section.

If we want to display a video stream from a file, we can run the following:

snapshot --gui --camera sample.mp4

If we want to display a video stream from a URL rtsp://localhost:8090/stream, we can run the following:

snapshot --gui --camera rtsp://localhost:8090/stream

Note that we can feed the --camera option with a file, a URL or a camera name. Lastly, the --timeout option can be used to specify how long the app should be searching for a video at startup, or when the connection is lost. By default, this is set to 30s.

Record a video stream

When you want to record snapshots from a video stream, you can use the --record option. For example, if we want to record a video stream from the default camera, we can run the following command:

snapshot --record

This will save snapshots of the default camera with the default values for the --interval, --duration and --folder options, i.e., every second for 10 seconds, for an unlimited time, in the ./snapshot folder. Most likely, you want to change these values. For example:

snapshot --record --interval 5 --duration 60 --folder /path/to/folder

this will save snapshots every 5 seconds for 60 seconds in the /path/to/folder folder. If the folder does not exist, it will be created, as long as the parent folder exists.

To ensure that the disk does not fill up the snapshots when you forget to stop the recording, the --max-snapshots is set to 10e9 bytes (10 GB) by default, which means that the recording will stop when the current session exceeds this size.

Using the configuration file

Instead of using the command line options, a cnfiguration file can be used. By default, the application looks for a file called config.json in the $HOME/.config/snapshot directory. If no configuration file is found, the application uses the default configuration which is equivalent to the default values of the command line interface (see snapshot --help).

Below an example of a configuration file is shown that has the default values:

{
  "gui": false,
  "list": false,
  "record": false,
  "camera": "default",
  "folder": "./snapshot",
  "timeout": "30s",
  "duration": "0s",
  "interval": "10s",
  "max-bytes": "10e9",
  "loglevel": "warning",
  "pattern": "[%Y-%m-%d %H:%M:%S.%e] [%l] [%s:%# @ %!] %v"
}

Naturally, you can change the values to your liking. For example, by setting the gui option to true, the application will open the gui by default. This is equivalent to running snapshot --gui. Note that the command line options override the configuration file options when they are given.

If you want to put your configuration file in a different location, you can specify the location using the --config option:

snapshot --config "$HOME/some/other/location/config.json"

Note that the ~ character and environment variables are expanded. Environment variables must be specified using the ${VAR} or $VAR syntax.

Set the logging level

By default, the logging level is set to warning. If we want to set the logging level to debug, we can run the following command:

snapshot --log-level debug <other options>

The following logging levels are available: trace, debug, info, warning, error, and critical.

Development

If you want to contribute to this project, you should start by reading CONTRIBUTING, and installing the project from source. This section provides information about: the tarball, the unit tests, and ways to debug the application.

Test

Googletest and QTest are used for building the unit tests and the end-to-end tests. To build the tests, the BUILD_TESTING option must be set to ON when configuring cmake:

./scripts/configure --build_type Debug -- -DBUILD_TESTING=ON

this will use the Debug build type with the tests enabled. To run the tests, run the following command:

ctest --test-dir ./build

Tarball

Additional information about the stand-alone tarball is provided here.

• snapshot is an executable in the form of a bash script. This script:
  • sets the LD_LIBRARY_PATH to the lib directory and runs the snapshot binary.
  • resolves the path to the script if it is referenced using a symlink.
• the runtime directory contains shared libraries and binaries that the snapshot script depends on. In case the project is built with the --shared option, the runtime folder will also contain subdirectories with the libraries of the Qt plugins. The runtime directory does not include the standard c/c++ libraries (libc, libstdc++, libm, libdbm, libpthread) together with the dynamic linker as they are assumed to be present on the system.
• snapshot_test is an executable in the form of a bash script. This script is only present when the project is built with the cmake option -DBUILD_TESTING=ON. If so, when running the snapshot_test script, all tests are executed.

Debugging

You can use one of the following ways to run the application with a video stream:

Using a file

A sample video file is provided in the tests/static. It can be played using the following command:

snapshot -g -c tests/static/sample.mp4

This opens the gui and plays the sample.mp4 file.

Using an http stream

If you have internet access, you can use the following command to play a video from a public http stream:

snapshot -g -c http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4

This opens the gui and plays the video.

Running the rtsp stream

By running the following command, a video stream is published using the rtsp protocol:

./scripts/rtsp-stream tests/static/sample.mp4 rtsp://localhost:8090/stream

This stream can be viewed using the following command:

snapshot -g -c rtsp://localhost:8090/stream

This displays the video stream using the GUI.

Running the udp stream

Similar to running the rtsp stream, an udp stream can be published using the following command:

./scripts/udp-stream tests/static/sample.mp4 udp://localhost:8090

This stream can be viewed using the following command:

snapshot -g -c udp://localhost:8090

License

This project is licensed under the MIT License - see the LICENSE file for details.

Troubleshooting

If you encounter any issues, please report them on the issue tracker at: snapshot issues

Contributing

Contributions are welcome! Please see CONTRIBUTING for more information. Also, read the section on Development for additional information.

FAQ

WSL2 fontconfig

On WSL2, if you encounter the following error:

Fontconfig error: Cannot load default config file

install fontconfig on your system as is describe on the website of Qt

Hardware acceleration

Issues with your graphics card need to be resolved by the user itself, as this application has no control over it. The following pages from the arch wiki are very useful when you encounter issues with hardware acceleration:

• General
• Intel
• Nvidia
• Nouveau
• AMD