Animal Cage Camera


Description

The ACC provides video that is synchronous with our subcutaneous transmitter recordings to within a twentieth of a second over any recording duration. The camera streams its video as separate frames at a fixed rate. These are received by the Videoarchiver process on the video recording computer, where they are assembled and compressed into a video that is synchronous with the local computer clock. Given that the EEG recorded by our subcutaneous transmitters is also synchronized to the local computer clock, the result is EEG and video synchronized to the same clock within a twentieth of a second. In the Neuroarchiver Tool, we specify a directory containing the video files, as well as a directory containing the EEG recording files, we can navigate through the EEG recordings and see the synchronous video displayed automatically.


Figure: Animal Cage Camera (A30234A). The A3034A mounts by cable ties to the pipes behind an IVC mouse cage, as shown here. Ethernet socket at the rear, on the embedded computer, as shown here.

The image quality we obtain from the ACC is far superior to that of low-cost CCTV systems. The ACC lens's depth of field and sharpness of focus, and the superb exposure compensation of the ACC's image sensor, provide clear, sharp images of laboratory animals in poorly-lit cages, even when the camera is only ten centimeters from the cage wall or ceiling. The ACC provides remote-control white and infrared illumination that we can use to enhance image contrast, take pictures at night, or to generate twenty-four hour illumination cycles.


Figure: Images of Brightly-Colored Object in White LED Light (Left), Infrared LED Light (Center), and White Plus Infrared Light (Right).

One use of video recordings is to track the movements of individual animals. Given that animals tend to remain in one piece as they move around, and rodents tend to remain the same color, we can treat animals as blobs in image analysis, and track them with video blob tracking algorithms. But when we have more than one animal in a cage, and the animals are near-identical in appearance, and keep vanishing underneath obsticals, and grouping together into larger blobs, video blob tracking cannot distinguish between the animals. But if we have subcutaneous transmitters implanted in our animals, we can use an Animal Location Tracker (ALT) to measure the approximate movements of each animal, compare these movements to those of the blobs produced by blob tracking, and so determine which blob corresponds to which transmitter, which results in unique identification of each blob. We call this disambiguation of the blob tracking by the ALT data. This disambiguation is possible only because the ACC videos are so well-synchronized with the subcutaneous transmitter system, and in particular the ALT's recordings of pick-up coil power reception.

Motivation

When commercial CCTV camera systems record continuous video, they produce a sequence of files on our data acquisition computer, each of which is supposed to span a specified length of time. When we view these files, we find that the length of time spanned by each file is a few seconds longer or shorter than specified. Each file has a name that gives its time of creation, and the difference in creation time from one file to the next differs by a few seconds from length of the video contained in each file. When we start viewing a new file recorded by a CCTV system, we must wait a few seconds before the picture establishes itself. As a result of these problems, we cannot rely upon synchronization between video produced by such systems and recordings obtained form our subcutaneous transmitter system. In practice the two chronologies disagree by tens of seconds, and in a manner that we cannot predict or correct for. Our Animal Cage Camera (ACC) is designed to solve these synchronization and viewing problems, and provide superb image quality in both light and darkness. Our ACC is, however, more expensive than low-cost CCTV cameras. The wide-angle lens of the ACC alone costs us $100, and the image sensor and readout electronics another $100. We sell the ACC for $700 in quantity ten, while CCTV cameras are available for under $70 in the same quantity.

Links

Animal Cage Camera (A3034): A high-resolution camera with remote-controlled white and infrared illumination.

Videoarchiver Tool: Manual for the Videoarchiver, a LWDAQ Tool, which records video from an Animal Cage Camera in such a way that it may be played back synchronously with EEG and ALT recordings.

Videoarchiver Source Code: The Videoarchiver TclTk program that includes the ssh, mplayer, and ffmpeg commands we use to stream video from the camera, segment and store it on our computer, compress and combine into synchronous files, and display on the screen.

Videoarchiver Libraries: Archive of libraries for MacOS, Linux, and Windows necessary to run the Videoarchiver in LWDAQ. Download, decompress, and place the Videoarchiver folder in LWDAQ.app/Contents/ to make LWDAQ.app/Contents/Videoarchiver.

Video Blob Tracking (VBT): A description of how we analyze video frames to obtain the coordinates of animal-like objects. This link leads to our GitHub repository, where we keep the developing software files.

Animal Location Tracker (ALT): A platform of radio-frequency pick-up coils that measures the movement of individual subcutaneous transmitters in a cage above.

Parts and Prices: A list of devices and their prices in various quantities.