Medical video recording

The role of image capture devices is now significantly decreasing. Mainly due to generally available cameras with a digital interface (digital cameras with an integrated video grabber), indirectly due to popular grabbing devices only supporting the classic video signal in PAL or NTSC format at the input. Thus, the use of these devices is limited only to processing analog signals from older analog cameras. Devices with higher resolutions are rare and therefore expensive.

This does not mean that such devices have no advantages, or that their use automatically degrades the quality of the resulting image. There are two basic types of capture devices:

• external – connected to the computer,
• internal – a card that is inserted into the expansion connector of a PC (e.g. PCI or other) or into a notebook (e.g. Express Card).

The first of them should be chosen only in the case of a higher necessity (e.g. a notebook without an expansion slot). They have the same disadvantages of devices working on external buses (discussed in the chapter related to the data stream) and analog (signal transmission, largely susceptible to interference, analog). Most of these devices are connected to USB, which puts an unnecessary additional load on the computer. Paradoxically, such grabbers are used on weaker computers - notebooks. As mentioned - a solution acceptable only in case of necessity.

Completely different comments may be given to devices of the second type ("expansion card").It is true that these devices suffer from problems with analog signal transmission, but when using the best transmission standard (at least S-Video) and decent cables, the quality loss will be imperceptible. They provide the best possible way to deliver data to the computer's processor, avoiding unnecessary image conversion from one color space to another (RGB to YUV for cable transmission and vice versa for display) and minimizing additional load on the computer processor. Having a good quality analog camera, there is no reason to change it to a digital camera with similar parameters (i.e. not an HD camera).

In order to unburden the computer, capture devices can immediately compress the video stream to reduce its volume. This only makes sense if this stream can be written to the computer's hard drive immediately without any modifications, or it is critical to use more frames per second due to compression. If the recorded image needs to be processed in specialized software before saving it to improve its quality or the compression offered by the card is too poor quality at present (MJPEG, MPEG 1, even MPEG 2 standards), and therefore the image will be recompressed - solutions this should be absolutely avoided (especially when the card compresses video in the MJPEG standard). The technical data of some raking devices often includes information that the device "supports" certain compression formats. This should be approached with caution - usually the compression is done by the computer's processor, and the card only gives it data.