Medical video recording

Video recording takes place in a separate window that opens with the Record button. User can open and close the recording window many times during the examination, or return to record a new video sequences from later stages. It is also possible to record single frames and a series of four frames in the window. The window is presented in Fig. 1.

Fig. 1. Camera recording window - an example image from a laryngovideostroboscope

The main part of the window A is the view from camera. At the top there are control buttons Band at the left tabs C. After opening the new window, there is only the recording tab with the camera symbol 1.

In the recording tab there are buttons with symbols of a movie, movie with a pause sign, series of frames and a single frame 2. These buttons are the default foot switch setting. By pressing one of the buttons, one of the recording options (video sequence, pause video, series of frames, single frame) is selected, which is to be operated by the foot switch at the moment. Depending on the camera configuration, these buttons may also affect the resolution of the recording (described in more detail in Appendix A).

Recording starts after clicking the Record button 3or pressing the foot switch. The recording will end after clicking the Record button again or pressing the foot switch. It is possible to pause and resume recording in one sequence by pressing the button with the pause symbol to the left of the Record button. Recording is ended by pressing the Record button. By pressing the button with the movie symbol with a pause sign, the user can start, stop and resume recording by pressing the foot switch.

It is required that the length of a single video recording should not exceed 400s. After a video has been recorded, frames representing the sequential recorded video sequences appear below the recording tab (the first frame of each sequence) 4.

An improvement in the program is the ability to record a recording that starts a few frames before the actual pressing of the record button. Such a solution was used due to the limited reaction time of the user from the moment of noticing the interesting image to pressing the Record button. The computer saves 3 to 20 frames (depending on the setting) before the button was pressed. The number of additional frames to be saved is configured in the camera settings.

During recording the recording time is shown in seconds (large numbers) and the current number of frames captured from the camera 5, but not yet compressed and not saved to the file (these missing frames are saved and compressed after the end of recording).

If it is required to preview the video image as large as possible, it is possible to enlarge it to the whole screen by double clicking on it with the mouse. You can then start and stop recording by clicking the button in the upper left corner (red frame), or by pressing the foot switch. The button appears as a solid red rectangle while recording. There is also a recording time counter and a frame buffer full indicator in the form of a blue frame with a bar of length and color (green, yellow or red) depending on the current number of frames captured. Also, when playing back a recorded video sequence in the recording window, you can enlarge the image over the entire screen in the same way. The play indicator and the start / stop button are a green rectangle during playback. To return to the recording window with all the buttons, double-click in the window with the mouse.

It is possible to record audio while recording video. This option is turned on in Video recording configuration (more about it in Appendix). If the sound recording is turned on, an additional cell appears in the recording window below the Cancel button (Fig. 2), which shows the oscillogram of the recorded sound.

Additionally, the recorded audio is saved as a separate .wav file, which allows it to be used for voice acoustic analysis.

Fig. 2. The process of audio recording during video recording

The Series button 6 allows recording four consecutive frames directly from the camera without recording a video sequence. A series of frames can also be collected with a foot switch (when the series button is selected 2. These frames can be saved from 3 to 20 frames before pressing the button, due to the limited response time of the user. The tab representing the series of frames contains four tiled frames from the series 7. The series is saved as a video with frames at half-second intervals.

In order to capture a single frame (take a photo), use the Frame button 8, or - after selecting the frames button 2 - the foot switch. The selected frames are represented by frame tabs marked with a yellow rectangle in the upper left corner 9 to distinguish them from the video. The collected single frames are additionally saved as a video with half-second intervals between frames.

On each recording or frame (before or during recording) it is possible to correct the brightness, contrast and hue (share of red and green components) with sliders 10.

It is possible to enlarge the image already during recording, using the buttons 10. After zooming in on the recording, it is possible to move it with the mouse, by left-clicking on the image and dragging.

The recording to be played is opened by clicking on the right tab (Fig. 3, tab 14). The Start 15 and Stop 16 buttons appear on the top bar (except for the single-frame viewing mode). To record another video after browsing, click on the recording tab with the camera symbol, which will open the recording window. It is also possible to delete recordings in the window by pressing the cross in the upper right corner of the right recording tab.

After recording, exit the window by clicking the Save button 12in order to save the recorded material. Clicking Cancel 13 will exit without saving recorded video sequences! After the recordings are saved, the first frames will appear in the test window. If single frames have been collected, the character fused into a movie with half-second intervals between frames is additionally saved. Such films are created separately for each subsequent opening of the recording window.

Fig. 3. Play recorded video in the recording window

In case of a power outage or any other cause of sudden shutdown of the program while working in the recording window, the recorded video sequences and the series of frames will be saved. When you restart the program and open the record window, the previous recordings will be placed in tabs in the record window.