One important problem in Musical Information Retrieval is Automatic Music Transcription, which is an automated conversion process from played music to a symbolic notation such as sheet music. Since the accuracy of previous audio-based transcription systems is not satisfactory, we propose an innovative visual-based automatic music transcription system named claVision to perform piano music transcription. Instead of processing the music audio, the system performs the transcription only from the video performance captured by a camera mounted over the piano keyboard. claVision can be used as a transcription tool, but it also has other applications such as music education. The claVision software has a very high accuracy (over 95%) and a very low latency in real-time music transcription, even under different illumination conditions.