In movie production, image (picture) and audio are recorded by different devices. When combining image and audio later in the process, the two types of information have to be synchronized. Usually, this is performed manually, by an operator assigning time codes to an audible “clap” for a slate with the visible closing of the slate. However, due to the nature of movie capture, this can be done only with a limited accuracy since the image or film is recorded at frame rates usually between 24 and 60 frames per second. Hence, the problem of 1/24 seconds or 1/60 seconds uncertainty between the visual clap and the audio may occur.
Although there have been a number of prior systems that are able to synchronize audio and image streams in a manual or automatic manner using slates, these techniques generally face the problem of subframe misalignment due to the sampling rate (frame rate) of the audio stream. The sampling rate of the audio stream is often much larger than that of the image stream, and the correct alignment point is almost always in-between two consecutive image frames.