Frequently Asked Questions Q: What is video latency? Why are the video and audio out of sync?A: Video latency occurs when a video image is produced (image placed on the screen) later than the audio signal is produced (sound from the speakers). This results in a lip-sync problem.
Video latency originates when the broadcast is slightly out of sync when transmitted. Normally, this issue does not occur on DVD players, VCRs, or cable TV signals (unless broadcast signals are not modified by the cable provider), because these signals are synchronized at the origin. However, satellite dishes may exhibit this issue.
The potential for video latency is present in all digital and analog televisions because the video and audio signals do not follow the same paths after the broadcast signal enters the TV. The audio signal is decoded and sent directly to an amplifier, and then is routed to the speakers. The video signal takes a completely separate and longer path to production. If the broadcast is slightly out of sync when it enters the TV, the result is unsynchronized output.
The transmission differential (and the length of the differential) change depending on the frequency (channel), weather conditions, the transmitter, proximity to the transmitter, and the fact that the broadcaster/transmitter attempts to keep the signal synced during transmission.
Due to the fact that there is not a common sync pulse between the audio and video signals, there is no real-time method of correcting video latency. The digital receiving equipment does not compensate or slow down the audio signal to sync the audio and video together.