Audio/Video out-of-synch AVI -> MPG

ppost · Post by **ppost** » Sun Feb 11, 2007 1:48 am

I've checked the archives and did not find anything like my problem. For the last year and a half I have been successfully taping TV programs and burning them onto DVDs with VS9. I capture them as AVI files by connecting a VCR connected to my computer, through my Sony digital camcorder to perform the analog-to-digital conversion. My project properties are:

NTSC drop frame (29.97 fps)
MPEG files
24 Bits, 720 x 480, 29.97 fps
Lower Field First
(DVD-NTSC), 4:3
Video data rate: Variable (Max. 8000 kbps)
LPCM Audio, 48000 Hz, Stereo

I edit out the commercials, and create video files using the NTSC DVD 4:3 option. I then burn the MPG file onto a DVD.

Recently I have been experiencing audio out-of-synch problems when converting the AVI files to MPG files. The out-of-synch problem is gradual - first noticeable at about the 20 - 30 minute mark, and getting progressively worse. At the hour mark, the audio is about a half second ahead of the video. The sound on the AVI file is fine when previewing on VS9 or played back using Windows Media Player. Conversely, the sound on the MPG file is bad when previewing on VS9 or played back using Windows Player. I tried not doing any editing, but the result is the same. I have tried switching to a different VCR, and I tried capturing directly from broacast TV - the result is the same. I am truly mistified since this process worked very well for some time. I have not (knowingly) made any changes to the VS9 setup, and I have Windows XP updates set to automatic. My hardware configuration is a Dell Pentium4 2.8mhz, 2.5GB memory, and 640GB hard disk spread over four drives. I defragmented the drives.

I'm stumped - any help greatly appreciated.

Pete Postlewaite

TDK1044 · Post by **TDK1044** » Sun Feb 11, 2007 2:07 pm

This is most likely caused by having the 'Smart Render' function enabled during the render. Disable this function and your audio sync should be fine.

ppost · Post by **ppost** » Sun Feb 11, 2007 6:02 pm

I checked File/Preferences/General, and Playback method is set to Instant Playback. Am I correct in the belief that this means SmartRender is turned off?

TDK1044 · Post by **TDK1044** » Sun Feb 11, 2007 7:37 pm

No, Sir. When you go to Share....Create Video File, click on 'Options' and uncheck "Perform Smart Render'.

ppost · Post by **ppost** » Mon Feb 12, 2007 2:50 am

Terry

I turned off SmartRender, but unfortunately my problem persists.

Pete

TDK1044 · Post by **TDK1044** » Mon Feb 12, 2007 12:50 pm

Hi Pete,

What are the properties of your captured AVI file? Is the field order the same as your conversion to MPEG2? Is the AVI audio captured as LPCM?

DVDDoug · Post by **DVDDoug** » Mon Feb 12, 2007 7:26 pm

I suspect your AVI file is bad. I call it "sneaky corruption", because when it's happend to me*, the original file played-back OK, but caused trouble when it was re-coded or re-multipexed.

My theory is that the A/V data structure is no longer "corrupted", but in the process of "fixing" the data, it goes out of sync. Imagine if you throw-out bad video frames, be keep the associated audio. That would create sync problems.

I have not (knowingly) made any changes to the VS9 setup, and I have Windows XP updates set to automatic.

I wonder if there is some process (anti-virus, etc.) running in the background and interrupting the CPU....?

I capture them as AVI files by connecting a VCR connected to my computer, through my Sony digital camcorder...

Via firewire, I assume? That's usually a very good procedure. Have you tried making a DVD from tape actually shot with the camera recently?

You might try recording to digital tape first, and then make a digital-to-digital transfer to the hard drive. I think camera and computer can adjust the digital transfer speed as needed so that you don't get any "real time capture" issues.

* In my case it was MPEGs. These types of problems seem be more common with more-compressed files than with AVI/DV files.

ppost · Post by **ppost** » Mon Feb 12, 2007 7:27 pm

Terry

Both the AVI & MPEG files are Lower Field First. The AVI Audio Format is PCM 32,000 Hz 16 bit stereo. The MPEG audio is LPCM 48,000 Hz stereo. What effect (if any) does the "Edit file format" parameter in Project Properties have? I tried capturing with both "Microsoft AVI files" and "MPEG files" parameters, but my problem persisted.

Pete

DVDDoug · Post by **DVDDoug** » Mon Feb 12, 2007 7:41 pm

Is this a mini-DV camera?

You should be capturing in the camera's native format, so that the computer doesn't have to perform any on-the-fly conversion.

AVI is a "wrapper" or "container" format, and it can contain anything from DivX to DV. If it's a miniDV camera, the AVI/DV file should be 13GB per hour. If it's a hard drive camera, the format will be MPEG.

The AVI Audio Format is PCM 32,000 Hz 16 bit stereo.

That's a little strange. DV audio is usually stereo 16-bit 48kHz LPCM or 4-channel 12-bit 48kHz LPCM. And again, that should be determined by the camera.

GeorgeW · Post by **GeorgeW** » Mon Feb 12, 2007 8:52 pm

DVDDoug wrote:
The AVI Audio Format is PCM 32,000 Hz 16 bit stereo.
That's a little strange. DV audio is usually stereo 16-bit 48kHz LPCM or 4-channel 12-bit 48kHz LPCM. And again, that should be determined by the camera.

I think what happened is when capturing the 32khz audio to DV Type-2, it made the audio 16-bit (instead of 12-bit). Changing the capture to DV Type-1 will probably keep it at 32khz 12-bit.

Regards,
George