Video settings

Capture rate

The Capture rate on the Video settings is only used for video capture and can be set independently of the marker capture rate. The setting is also individual for the cameras so that you can capture at different video capture frequencies.

The maximum capture rate can be increased by reducing the Image size. The current capture range is shown next to the capture rate. In the Project options dialog the Image size must be changed first to get a higher frequency. However, in the Camera settings sidebar the Image size will be reduced automatically when choosing a higher frequency.

For an overview of maximum capture rates for each camera model, see Qualisys video sensor specifications (in-camera MJPEG) when using in-camera MJPEG compression and High-speed video for uncompressed video.

It is possible to capture short video sequences with Qualisys cameras that are not configured for high-speed video. The capture rate is then limited to 30 Hz, even if you use a reduced image size.

Exposure time

The Exposure time setting changes the exposure time for video mode. The setting can be set individually for each camera.

The setting sets the exposure time in microseconds. The maximum exposure time is up to 60 microseconds less than the period time, i.e. 1/capture rate.

Flash time

The Flash time setting changes the flash time for video mode. The setting can be set individually for each camera.

The setting sets the flash time in microsecond. The maximum flash time is always limited by the exposure time but there are also other limitations. First of all the flash time cannot be longer than 2 ms. The other limitation is that it can only be one tenth of the period time of the capture rate. For example, if the capture rate is 200 Hz the maximum flash time is 500 μs.
The IR flash does not contribute much when you capture video. Therefore, it is often a good idea to set the Flash time to its minimum of 5 μs.

Gain

With the Gain option the intensity of the video image can be increased. Select the desired gain from the drop-down list. The available values are 1, 2, 4, 8 and 16 (for older camera models the maximum gain is 4). The default value is 1 except for the Oqus 2c-series and Miqus Video where it is 4, or it is set automatically when using auto-exposure. Use the Gain option if the exposure time and aperture is already at their maximums.

All cameras, except the Oqus 3 and 5 series, have analog gain before the image capture and therefore the image quality is not decreased at the same degree with increasing gain. The number of gray scales in the image is also the same for different gain settings.

The Oqus 3 and 5-series have digital gain, which means that the intensity of the image is just multiplied with the desired gain. The result is that image quality and number of gray scales are decreased.

The Gain option is available on the Camera settings sidebar for all cameras except the Oqus 3- and 5-series.

Image size

With Image size it is possible to change which part of the image that is captured in video mode. The setting can be set individually for each camera. Use the maximize button to reset the selected cameras to the maximum image size.

The selected image size will be shown with a red square in the video preview window. The frequency range will be updated automatically when you change the size. The camera will still capture video outside the rectangle in preview, but when you make a measurement the image is cropped.

The image size is specified in Left and Right, Top and Bottom, where the Left and Right values can only be specified in certain steps depending on the camera type. The step size for the current model is displayed next to the settings. For an overview of the maximum image size for each camera model, see Qualisys video sensor specifications (in-camera MJPEG) and High-speed video.

Notes on image size for specific camera models:

  • In the uncompressed mode of Oqus 2c, 5+, 6+ and 7+ series cameras the image size is only limited in the y-direction when increasing the capture rate. However, when increasing the capture rate on the Camera settings sidebar, the image ratio is kept constant. You can then increase the width of the image size by dragging on the red rectangle.

  • The image size of the Oqus 5 series camera can only be changed in the y-direction. This is because the frame rate on this sensor will not be increased when changing the number of pixels in the x-direction.

  • The x size of the Oqus 3 series camera must be at least 160 pixels. The x size of the Oqus 3+ series camera must be at least 144 pixels in Standard mode and 72 pixels in High-speed mode.

  • The In-camera MJPEG mode for the Oqus 5+-series has a larger maximum image size because it compresses the image in the camera.

Image resolution

The image resolution will change the quality of the images that are captured by Qualisys cameras according to the options below. The setting can be set individually for each camera.

  • Resolution
    Set the number of pixels that are captured, e.g. with 1/4 resolution every other line and column is deleted. Choose the resolution for the camera from the options below.

    • Full - Use all of the pixels

    • 1/4 - Use every second pixel in x and y direction

    • 1/9 - Use every third pixel in x and y direction

    • 1/16 - Use every fourth pixel in x and y direction

    • 1/36 - Use every sixth pixel in x and y direction

    • 1/64 - Use every 8th pixel in x and y direction

    • 1/256 - Use every 16th pixel in x and y direction

To optimize the memory usage there is a column of black pixels to the right in the image. This is especially visible at 1/64 or lower resolution.

Notes on image resolution for specific camera models:

  • The setting is not available for the Oqus 2c, 5+ and 7+-series cameras. If you want to reduce the image size on those cameras you have to use the Sensor mode setting, which has the advantage of also increasing the maximum capture rate. For more information, see chapter Sensor mode.

  • The Oqus 4-series camera cannot handle full resolution for video images, therefore the maximum image resolution is 1/4.

Video compression

The Video compression option can be used to reduce the video file size. By default the Mode is set to In-camera MJPEG for all cameras that support that option. You can set the Compression quality of the MJPEG compression to change the quality and file size of the video; the default is 50. Increasing the quality will lead to larger images and in some cases this means that not all of the video images can be sent during the capture. These frames will be fetched after the capture is finished.

For Miqus Video, the Video compression setting is not available. Miqus Video cameras always stream video using In-camera MJPEG.

The default mode on the other cameras is None for uncompressed image and maximum quality. If the file is uncompressed it may not play at the correct speed in most external programs.

Switch the Mode setting to Software to specify a codec on the computer for compression of the video.

Choose a codec from the list on the Compression codec line to activate it. The codecs in the list are the ones that are installed on your computer.

The codecs are then grouped in Recommended codecs and Other codecs. For more information about the recommended codecs, see chapter Recommended codecs.

If none of the recommended codecs is installed on the computer, there are no alternatives under the Recommended codecs heading. Download links for the recommended codecs are available at https://www.qualisys.com/info/recommended-codecs/.

If available, the settings for a codec are opened with the button on the Configure codec line. The settings depend on the codec, please refer to the codec instructions for help on the settings.

Click on the button on the Codecs recommended by Qualisys line to go to a web site with links to codecs.

Color/Grayscale

The Color/Grayscale option is only available if you have connected an Oqus 5-series camera with a color sensor. For the color cameras you can select between the following options for the color interpolation.

  • Grayscale
    Capture the raw black and white image. The image will be checkered because of the color filter in front of the sensor. This pattern cannot be removed because the filter is integrated with the sensor.

  • Color
    Use bilinear color interpolation to get a color image.

    If you want to use the color interpolation on 5-series with the Image resolution option, then you must select 1/9 or 1/36 for the color interpolation to work. The other options delete the color information from the sensor.

It is important to notice that the color interpolation is time consuming and therefore the RT frequency will be much lower with color interpolation.

In a measurement the color interpolation is done after the video has been fetched from the camera, so it does not change the maximum time that you can capture video.

Auto exposure

The Auto exposure option is available on Miqus Video and Oqus 2c cameras. With the auto exposure the exposure time and gain is controlled automatically so that image is bright enough. When the camera is using one of the predefined presets then the auto exposure is always on. For the Custom preset it must be turned on with the Auto exposure option.

When turned on there are two additional settings Auto exposure compensation [EV] and Auto exposure area. The Auto exposure compensation option controls how bright the image will be. Increase the value to have a brighter image and decrease it to get a darker image. This option is also available in the Camera settings sidebar in preview.

By default the whole image area is used to calculate the brightness of the image. The area used in the brightness calculation can be set with the Auto exposure area option. In this way the camera can calculate the brightness on the part of the image that is most useful. This can be used for example when there is a bright window in the image. It is easiest to define the area with the Auto Exposure tool in preview, see chapter 2D view toolbar.

Color temperature

The Color temperature setting is only available for the Oqus Color video (2c) camera. With it you can adapt the color temperature used for the white balance in the video. If you use the wrong option the colors may be very wrong, so it is important to test the different options to find the best one.

  • Daylight
    This option uses a color temperature that is most suitable for daylight. It works best outdoors, but also works well if you have large windows.

  • Office lighting (Cool white fluorescent)
    This option is for bluer type of lights. It is usually not the best option if you mixed types of lighting, for example if there are windows.

  • Home lighting (Incandescent)
    This option is for more yellow type of lights, like light bulbs. It is usually not the best option if you mixed types of lighting, for example if there are windows.

  • No color correction
    For this option the color temperature is not adjusted at all. It can for example work well in situations with mixed types of light.

Sensor mode

The Sensor mode option can be used to reduce the resolution to get a higher capture rate while keeping the same field of view. The option is only available for camera models that have more than one sensor mode. The setting can be changed individually on each camera and also for Marker and Video mode separately. The sensor mode setting can also be changed on the Camera settings sidebar. For an overview of available sensor modes per camera model, see Qualisys video sensor specifications (in-camera MJPEG) and High-speed video.