Voip Blog
How Sound Synchronizes Up With Pictures
Wednesday, May 07, 2008
In this short film from 1929, a couple of animated characters explain the process of synchronizing sound with pictures--something that back in those days was still relatively uncommon in films.
What I find interesting about this process is that they described microphones in terms of the telephone, i.e. it's it just like a telephone. It's an apt description, given the film was made by Western Electric, the manufacturing arm of the Bell System (AT&T and associated companies) until it was ordered to be split up in 1984.
Nearly 80 years later, of course, getting sound and video synced up on motion pictures is old hat. But where it has been a challenge in recent history is in another promised innovation from Ma Bell--video calling. Even into the early 1990s, AT&T was putting out ads saying video calling was going to be a reality--soon.
Now there are a number of solutions for video calling, and they all have to solve the audio/video sync problem. Unlike with recorded video and audio, where it is generally trivial to fix any synchronization issues, you don't have the luxury of time in real-time video calling.
In my experience with a number of different video calling solutions, when push comes to shove, video is put aside in favor of maintaining audio quality. The theory is that you can still have a conversation with audio, even if the video isn't up to snuff. Also, video takes substantially more processing power and bandwidth than audio.
The codecs used to compress audio and video take this into account, though it is a challenge to get back into sync when you get out of sync. With many video calling solutions, it can take several seconds to get back into sync. One company in particular has patented technology they employ to keep audio and video synchronized, even in changing bandwidth conditions.
