Why is Audio and Video out of Sync during recording?

Question

I make a 30 second recording using a webcam on a laptop. When I play the .avi file afterwards, the audio and video are out of step. The sound starts arriving about a second after it should do and gets increasingly delayed.

Why is this?

Whilst I am making the recording, I can see the video that is being captured being displayed on the laptop monitor. I can actually get lip synch if I s-p-e-a-k l-i-k-e t-h-i-s.

I clap my hands at the start of the video. When I watch the video afterwards, the sounId is delayed by about a second.

The audio track continues for about ten or so seconds after the video component has finished. (A still image remains in the video player while the voice continues.)

I can fix this problem after the recording (laboriously), but I want to have the recording work properly in the first place.

The webcam is a BisonCam NB Pro integrated into the laptop. It is a 2 Megapixel camera that can record at 15 fps. The CPU is an Intel dual core T4200. The machine has 4GB of RAM. I am saving the recording to a file on a ramdisk, so I don't think the hard drive is the problem. I am using BisonCap to record, the software that came with the computer. I have set recording for 15 fps.

Please help!

Answer 1

You should check your recorded video with MediaInfo. Regarding your problem, it shows,

• if the durations of the video and the audio is the same or not,
• if the interleave of the audio (the starting offset) is set correctly
• in which sampling rate your audio was recorded.

Then, I would import your video file into Audacity (which imports only the audio, of course).

• On the left side of each track you find the sampling rate, too. Is this the same sampling rate as being reported by MediaInfo?
• Does Audacity play the audio too slow, too?

My impression from the symptoms that you describe is that the audio is recorded at a certain sampling rate, but reported as a lower sampling rate, or not at all.

Try to modify your sampling rate, either in your recordings settings, or in the Windows system. On Win7, it's under Control Panel->Hardware & Sound->Manage Audio Devices->Recording. There, select your microphone, then Properties->Advanced. There you can change the sampling rate.

If changing the sampling rate doesn't help, then you can only try another webcam software, or record the audio independently.

Answer 2

There are quality settings for both the audio and video recording. Have you checked out the video capture settings? Maybe some adjustment here would get the audio and video back in sync.

The picture is from this Dell support site. May be some more useful info there.

Also, just in general (sorry if it's obvious) are you sure your drivers for the webcam are up to date?

Answer 3

Best way to check if it's out of sync or drifting, or both would be make a recording, clap with your hands once at the beginning and at the end. Check if the sound is earlier or later at the beginning or the end. Then to resync, use an Non Linear Editing program to align and possibly re-time the audio, retiming the video will look much worse than fixing the sound. Also recording at 15fps rather than 30 won't look great.

Answer 4

I think you should try another program first and see the result. Maybe the software is the reason or tweak the settings of yours. Also try to close any other software which is running at that time like antivirus programs etc.

Answer 5

The quick answer that worked for me: do NOT save your captured video to a drive on the computer, save it to an external drive that runs at 7200 RPM (many are 5400).

This problem was driving me crazy. I checked so many blogs, FAQs and help lines, but nothing worked. Finally a salesman at B&H Photo in NYC pointed me in the right direction (this is not an endorsement, but I do want to give credit where credit is due, and his suggestion definitely solved my problem!)

Some detail: I was capturing old VHS tapes from a tape deck directly to PC; an old Gateway EDX4840-15 workhorse. I use Media Express (not crazy about the software, but it worked) capturing to AVI files (the only choice, oddly). Originally I captured to the internal drive and all the captured video would gradually get out of sync, as described. It would start out synced, gradually getting more and more out. Capturing to the external drive at 7200 solved the problem. The drive I used is a G-Drive Mobile USB 2TB, but I suspect any 7200 drive would work. After the capture I move the files to my regular 5400 drives for long term storage (I have a lot of them). Note: once I mistakenly captured to an external 5400 drive, and the sync problem re-emerged, so the faster drive is definitely the problem solver. Now that I think of it, if you have a 7200 internal drive, maybe that would work okay. I don't know the speed of my internal drives at the time of this writing, but it's a thought.

Answer 6

I am experiencing this problem and I am implementing a solution. Presently I used a program to extract the audio into .mp3 format separate, and Windows Movie Maker to extract the video alone into a .wmv silent video. Since I have the .mp3 file I loaded it into Audacity so that I can add and subtract time in order to synchronize the audio file manually into Windows Movie Maker along with the .wmv silent video. Having split the out-of-sync video into constituent video and audio parts, I am going to use Windows Movie Maker to integrate an edited version of the audio file on the fly as I edit it in Audacity.

Answer 7

I had the same problem with audio being out of sync with the image, recording from my webcam using screen recorder. In my case it seems it was caused by the time it takes for the webcam to activate. I changed 'delay before capture' to 2 seconds and it seems to have fixed the problem.