Why do the sound and video sometimes get out of synch when ripping DVDs?

August 31, 2007 4:31 AM

When ripping some DVDs to my hard drive, why do the sound and video get out of synch?

I generally use Mac the Ripper for doing this, and yes, I only do this for DVD's that I own. My question is that for some DVDs (particularly "Almost Famous", and "Woodstock: the Movie"), the audio gets out of synch with the video by several seconds. For other DVDs ("Rock Star", "24 Hour Party People"), it works just fine. Why does this happen, and is there anything that can be done to adjust for it?

posted by psmealey to technology (8 comments total)

I use mencoder (via AcidRip) for the same job, and sometimes I end up with rips that have a consistent half-second or so between audio and video for the whole movie; audio and video don't drift apart, though. Fortunately mplayer has keyboard controls for adjusting A-V delay (+ and - keys) so I've never bothered re-ripping. Perhaps you might try out OS X versions of mencoder and mplayer on your problematic discs.
posted by flabdablet at 5:42 AM on August 31, 2007

From my experience, two things can desync a movie encoding.
The framerate of the images is slower than the framerate at which the sound is set.
Maybe the video is at 30 fps but the audio is set for 29.97 fps, and so on. Make sure to check that.

Also it's possible that high cpu usage while encoding could result in unexpected artifacts.
posted by PowerCat at 5:43 AM on August 31, 2007 [1 favorite]

Where I've had rips which played poorly, I found that VLC plays them OK.

Also, try Handbrake.
posted by pompomtom at 6:15 AM on August 31, 2007

Just ripping, or re-encoding?

Because ripping is really just copying the files. If it's not playing right, I would look first to the player software, not the ripper.
posted by smackfu at 6:26 AM on August 31, 2007

PowerCat has said the most useful thing so far, but consider this another vote for HandBrake
posted by bryanjbusch at 6:57 AM on August 31, 2007

You're right, of course, smackfu. I inaccurately phrased my question/issue. It's not in ripping the DVDs. Mac the Ripper works just fine for this purpose. The problem is in re-encoding them. The application I use for this is Cinematize. It works perfectly most of the time, but a little more than 10% of the time, the audio and video are de-synched as described above.
posted by psmealey at 6:59 AM on August 31, 2007

With NTSC, the correct frame rate is 29.97 frames per second. If you encode with 30 frames per second, sound and visuals will desync.
posted by Steven C. Den Beste at 10:22 AM on August 31, 2007

It's possible you're losing sync because of gaps in the timestamps of the audio samples...If so, MPEG Streamclip can fix those audio timecode breaks.

I wouldn't hold out much luck that HandBrake would reencode without losing sync, but it might be worth a shot if nothing else works.
posted by jbrjake at 7:00 AM on September 1, 2007