I was asked to check out a possible Lip Sync issue for a low powered television station. They were getting reports that their programs were out of Lip Sync but it was hard to tell. While there are test generators that put out a Lip Sync test signal I do not have one to plug into their encoder.
So I made my own.
Using Final Cut Pro I made a moving bar that crossed the screen from left to right, I put a 15 frame audio tone at the mid way point and placed corresponding bars at the middle of the frame to mark were the beep should occur. Then I added smaller black bars at 2 frame intervals on either side of the center bar so you could gauge the amount of offset.
While editing this clip I set the tone to be off by a few frames one way and then the other to see it I could detect it. As i have read, it’s much easier to detect when the audio occurs first or early, this is because we do not experience this in the real world, we see the lightning and then hear the thunder, not the other way around.
I have heard that some monitors have their own lip sync problems as some take longer to display a frame of video and that will cause the audio to be early. It’s a good idea to check you monitoring systems.
Two files are available for you to download, the first is an SD version and the other is an HD version of the Lip Sync Test. These are MPEG4 files that should work in your iPhone, iPad or even iPod Touch. I have even used them on my Apple TV. On the SD version the black bars are 2 frames apart, and on the HD they are 4 frames apart.
The SD video file can be had by,Right Clicking on this link and Down Loading - SD Lip Sync Test Clip (4MB)
The HD video file can be had by,Right Clicking on this link and Down Loading - HD Lip Sync Test Clip (7MB)
For this test I only needed analog video, as thats what the input to the encoders. The next question was how to get if from the computer to actual video and audio. Well Apple has provided for that in the form of two adapters.
Using my old iPod Touch I can plug either of these adapters in and get either NTSC video with audio all on RCA plugs or I can get HDMI out to feed directly into a monitor, or even that new JVC monitor that will convert an HDMI input into HD-SDI for me. So for this test I was using just the A/V cables to get the Lip Sync test out and it worked just great.
The SD video file for iPhone, iPod Touch or even iPad can be had by,Right Clicking on this link to Down Load – Lip Sync Test Clip