MPEG Video Not Syncing with Audio

  • Thread starter Thread starter Guest
  • Start date Start date
G

Guest

I have a 371 meg MPEG with sound that I recorded off my TV. I just edited it
and got it down to about 19 megs. My problem is this. When I import the
video it previews great (sound/video together), however when I drag the (auto
divided) clips down to the timeline it because out of sync. I then go ahead
and save it to my computer (tried multiple formats) and still the movie
starts with video correctly, but the sound is like 40 seconds on down the
road.

Any ideas?
 
Excerpted from http://www.newcyberian.com/howto/dvdauthoring.html

The causes of AV out-of-sync are manifold. They can occur during
capturing, editing, compressing, and rendering. With the ever increasing
computation power of an average PC A/V out-of-sync is becoming less a
problem, albeit still found in many DVD masters that were sent to us.
Studies showed we human can tolerate audio lagging video more than audio
leading video. The A/V out-of-sync acceptability thresholds are 185 ms for
audio lagging video and 90 ms for audio leading video.

Common causes of AV out-of-sync are:

a.. Drop-frame is the number one culprit for AV out-of-sync. Drop-frame
occurs when the computer is not fast enough to process the video and audio
stream. You can minimize the occurrence of drop-frame by having computer
with powerful CPU, a hard drive with high spinning speed and seek-time, and
you should optimize the performance of your hard drive by defragmenting it
from time to time.
b.. Choose the mismatched attributes for source audio and capturing
settings. For example, if the DV audio is set at 12-bit 32KHz and you
choose the 48KHz project setting for capturing, AV out-of-sync is likely to
occur.
c.. Do not use the hardware profile for capturing. Good capturing
software usually have a set of hardware profile for you to match your
device. If your device is not in the list you can only choose the generic
profile. Doing so will leave a lot of guess work for the software. For
example, the audio frequency of certain brands of camcorders might not be
truly 48KHz but 48.0005KHz. Without the hardware profile to compensate this
discrepancy the captured audio will have many sample cycles less then the
source audio; 5 x 3600 = 18,000 cycles to be exact in one hour.
A good way to check whether AV out-of-sync occurs is to demux the audio and
the video, i.e. separating them as two individual files. Play each file in
any compatible players (such as Windows Media Player) and then observe their
lengths. If the lengths differ than there is AV out-of-sync for sure.
 
Back
Top