Hello. Yes, such motion capture software and hardware is now available. The one that we use is called VICON. It works with six cameras and you can capture the gait from any side including front, back and sides views simultaneously. In fact, it provides a 3D model of motion for you. Also, you can capture the video using two cameras and then analyze them with MATLAB. but you need to write the code with MATLAB and you may not get very accurate results with it.

Thankew mam...but i want to firstly capture videos then want to use MATLB ,so i need only two cameras, but is there any cameras that works insynchronization with each other

Hi

Prior to responding to your question, I should present this info before

1. Yes, you can capture 3D kinematical data with two cameras but it needs the mathematical operation called DLT.

2. The cameras’ positions are very important when the numbers of the camera are limited. The optimum position of the camera's lenses relative to each other and the ground is 90 to 120 degree. It is also stated, that the cameras’ positions should stay perpendicular to the planes of motion.

3. The reason to use more cameras in the lab is to prevent the marker loss as result of the inability to see the markers (motion of the hands during the gait) or the marker merging (two markers will be seen as one) during the data acquisition. (basically, labs will use 6, 8 or 12 cameras setups).

4. There are three types of cameras that can capture the kinematical data. These are including the passive marker systems, active marker systems, and marker-less systems. The passive marker systems have infrared light diodes that can produce red light in the lab and the camera lenses capture the reflection of the red light from the markers. The active marker systems use an electrical diode instead of the marker (which means that the marker itself produce the infrared light) and the cameras’ lenses capture the light directly. However, marker-less systems are like normal cameras that can acquire the data. However, right now the utilization of the marker-less systems in the laboratory setups becomes distinct. Because the body segments have mass, therefore acquiring the exact location of the body in time based on the camera pixels are hard. So, researchers use a single point (usually the center of mass or rotation) for this matter and distinguished it with the prisms or markers.

5. There are different brands that can be used for your research. These brands are including Vicon, Motion analysis system (Falcon), Qualysis, Optotrack, and etc. recently the Vicon systems are becoming popular because of easy utilization and calibration.

6. During your research project, the synchronization and the calibration are very important. We have the temporal and spatial synchronization. The temporal sync is defined as triggering the cameras and other data acquisition instruments at the same time (the central command unit of aforementioned brands do so for you). If you did not use those brands central command unit should be used to trigger all the cameras at the same time. The spatial sync is defined as syncing the cameras to the specific coordinate systems and the zero point. There are many coordinate systems, but within the biomechanics, the global coordinate system (GCS) will use frequently. The calibration of the cameras was performed to identify the relationship between the pixels and the size of the cube to illustrate the kinematical data accurately.

7. If you want to use usual cameras like Sony or etc to capture the kinematical data there are many different techniques, tips, and roles exist that you should obey to acquire data accurately which the synchronization is became really ease relative to does difficulties (including image processing that you should perform in the MATLAB or other computer languages). So, I recommend that use one of the aforementioned brands to diminish the possible unnecessary difficulties that existed in 1970 projects. Right now, with these brand new capturing data cameras those problems do not occur and researchers can focus on their project goals.

However, I cannot push you to utilize one the brand new systems, and if want to use normal cameras for your research probably you can do that an there are tons of articles and literature out there to help you to do so.

Best regards

Alighanbari

Hi

For the frame rate of the camera, the higher the better is the answer. The frame rate act as sampling technique which digitalizes the analog input. The minimum sampling frequency is the sampling theorem of Nyquist which state that the minimum sampling rate from an analog signal should set 2 times larger than the highest frequency of the signal. For movement of the body, the highest frequency is 14 frame per second. So, the frame rate of 28 can be adequate, but if you choose higher frame rate your signal becomes more likely to the real analog signal. Therefore, researchers tend to choose higher frame rate. But other factors can affect the frame rate including the cube size, the distance between the camera and center of the cube, the speed of the movement, and etc. usually biomechanists use 150to 240 frames per second as frame rate for acquiring the kinematical data from the camera. There are many

factors exist to consider like shutter speed, exposure time, aperture, f-stop, capturing time, cube size, calibration technique, resolution, and etc.

Presenting them here are impossible better to read previous literature to know how set does.

Best regards

Alighanbari

Thanks Mohsen Sir for your valueable answer but sir other factors that you have mentioned, i found no information on it in the literature surveys..Can you provide the detailed inf about it? It will be very helpful for me

Thankew Mohsen sir, for providing this great information by giving your time

Hi,

I think Mohsen had already explained in very detail. However, I think you need to visit some gait laboratories which actually do such studies and you will learn how they install cameras and how they do all kind of analysis. I can suggest you PGI Chandigarh gait lab, which do such gait studies.

regards

Bahadur Singh