Hardware Reference
In-Depth Information
Finding out your webcam's capabilities
Before we start grabbing videos with our webcam, it's very important that we find out
exactly what it is capable of in terms of video formats and resolutions. To help us with
this, we'll add the
uvcdynctrl
utility to our arsenal, using the following command:
pi@raspberrypi ~ $ sudo apt-get install uvcdynctrl
Let's start with the most important part—the list of supported frame formats.
To see this list, type in the following command:
pi@raspberrypi ~ $ uvcdynctrl -f
List of frame formats supported by webcam
According to the output of this particular webcam, there are two main pixel
formats that are supported. The first format called
YUYV
or
YUV
4:2:2
, is a raw,
uncompressed video format, the second format called MJPG or MJPEG, provides
a video stream of compressed JPEG images.
Below each pixel format, we find the supported frame sizes and frame rates for
each size. The frame size, or image resolution, will determine the amount of detail
visible in the video. Three common resolutions for webcams are 320 x 240, 640 x 480
(also called VGA), and 1024 x 768 (also called XGA).
The frame rate is measured in
Frames Per Second
(
fps
) and will determine how fluid
the video will appear. Only two different frame rates, 15 fps and 30 fps, are available
for each frame size on this particular webcam.
