Addressing Audio-Video Lip Sync at the Baseband Level
March 20, 2006
Part 3: Tools to Help the Process Now that you've taken inventory of any piece of audio and video equipment that could possibly add a delay to a signal, what tools can you use to determine any errors? There are some on the market from companies such as Calrec, DK Audio, Pixel Instruments, Sigma Electronics, and Vistek. Some tools are used offline during setup, while others are meant for online monitoring. However, even if you don't have access to these tools, you can still make fairly accurate corrections by carefully monitoring the audio and video at each point in the signal chain, inserting delays where appropriate, and comparing the audio and video as you adjust the delays. A video of a "talking head" (and a speaking one too) is good source material; just make sure the source material is in sync when played out. If you have patch points along the signal chain and a quality control station already set up, so much the better. But a roll-around cart with a video monitor and an audio monitor panel with loudspeakers and level indicators (all with appropriate inputs for the type of signals you need to monitor) will work just fine. Make sure the video monitor itself doesn't have any inherent delays, and that it's large enough to clearly see the speaker talking. Also include some external audio and video delays that can be inserted, even if only temporarily during testing, and make up whatever cables you may need so you don't have to go looking for them later.
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