Testing a video transmission system includes generating an optical signal and varying the colour by sweeping through a colour range. A first optical sensor captures the optical signal at intervals to generate frames. Transmitted frames are received by a second communication device. Received frames are provided to a display of the second communication device to reconstruct the frames. Colour information of frames displayed is obtained by a second optical sensor. Colour information of successive reconstructed frames is compared to determine deviation in capture rate of two successive frames of the first optical sensor, delay between capturing a frame by the first optical sensor and displaying the frame by the display, deviation in display rate of two successive frames displayed by the display and/or a loss of a frame. Audio information may be utilized in video and, conversational latency, synchronization between video and audio, and audio synchronization measurements.