Gap between clips produces A/V de-synch. Solution ?

[ADLANCAS]

During capture, if the tape has a gap (signal vanish) between first record and another part of the movie, captured file has no more A/V synchronism.
This can happens also when a part of tape is damaged.

I've made a lot of tests using VirtualVCR and IUvcr.
IUvcr has a good advantage in this thema, because it has a function "Stop when signal vanish", which works very well.

The problem is when the tape has parts little bit damaged, it means, Videorecorder starts again "Auto-tracking" and after that, file capture is not more in synch.
IUvcr can't detect such problem and VirtualVCR unfortunatelly either.

Is there a way to avoid this behaviour ?

Thx,

Alexandre

[2ZOD.COM]

I noticed a lot of problems with choppy video losing audio sync when I captured with IUVCR. Whenever it did that, I captured the video uncompressed, and it fixed it. The file sizes were huge, but it worked.

A more practical option would probably be a time base corrector. That should clean up the signal, so it's just a constant feed. (I might be wrong about this, but from my understanding that's what one does)

[ADLANCAS]

Even after segmented captured files ?

[2ZOD.COM]

No, I always just captured the video all in one shot.

The main problem I was having is I think HuffyUV would have problems when the signal was really messed up, so uncompressed was ideal.

Check out the help file in iuVCR. Ther's a section called "Capture Tips", and it shows a screenshot with all the settings to get good captures with good a/v sync. If I have a clip that's over an hour, the only way I can get good sync is with those settings.

[bastel]

If you use avi_io you can tell it that your source is 25fps (or 29.97 <-- never tested that). The resulting avis will be 25fps, no matter how many frames are missing in between. Perfect sync. Period.

(I have a certain vcr that drops frames when you capture with 576 lines but does full frame rate at 575 lines. Before I found that out I had to live with those dropped frames for some captures. 30% frame drop but perfect sync thanks to avi_io.)

bas

ps: if you got long static noise parts huffyuv might bug out unless you enable the full output buffer, which in turn doesn't work well with avi_io - you are getting disk full before it is full. that's the bad thing about all this. but the only one.

[ADLANCAS]

@2ZOD.COM
Thanks for the tip!

@bastel
Avi_io works on VFW. My PCTV has a driver WDM. Thanks anyway!


Other experiences ?

[mkanel]

Adlancas,

I've also had sync troubles when capturing from tape with VirtualVCR and IUVCR. I get very good sync with VirtualDubMod. I also had good results with Avi_io's trial version. I also have a PCTV card and use these WDM drivers http://btwincap.sourceforge.net/ I've used them with WinME and Windows XP.

If your picky you may notice the audio is delayed with VirtualDubMod captures, on my system it's delayed by about 170ms from the first captured frame to the last. IUVCR corrects this automatically but then loses sync when capturing from tape. It's much easier to correct the offset in the VDM capture. You can use IUVCR to determine the approximate audio offset, it tells you the offset whenever you start a capture (it should do so with the default settings) Good luck.

Mike.

[ADLANCAS]

@mkanel

Normally, I don´t have problems with A/V synch.
Only when it appears Tapes with gaps (for example 5 seconds) between 2 clips.
Is this your case ?

[mkanel]

Adlancas,

I always have a sync problem when capturing from tape unless I use VirtualDub(Mod). AVI_IO seemed to work also but I only used it a little with the trial version. I'm sure that my player doesn't put out a steady frame rate, it seems to drift slightly over time.

Before I began using VirtualDub I did notice that sync seemed to be worse after some gaps. VirtualDub has no problem maintaning sync even with gaps.

My only sync issue now is a constant offset of the audio throughout the captured avi. I correct this with avisynth but it can also be corrected in VirtualDub or VDM. In avisynth "DelayAudio(-.17)" The delay may be different on your system.

This has worked well for me, I assume it will work for you too but everyone's system seems to be different, otherwise we would have just one perfect answer and this would be real easy.

I hope this helps. Mike.

[ADLANCAS]

@mkanel
Thanks for your info!

I have some news!
I´ve just captured (2 hours) in VirtualVCR from a tape 8mm WITH GAPS and...

A/V was perfect !

Someone can explain me ? :confused:

It depends on type of Tape, Videocassete player or what ?

Thanks,

Alexandre

[mkanel]

@ADLANCAS,

I'm glad to hear you had a successful capture. Did it just start working? Or did you change something? If it's working you might as well just keep doing what your doing. A lot of people report success with VirtualVCR, I just had another look at it and realized one of my basic settings was wrong (PAL instead of NTSC) so I'll give it one more try on my next capture.

Mike.

[ADLANCAS]

I had a sucessfull capture with a 8mm TAPE.

I didn´t change anything and unfortunetelly, I´m sure that on the next capture using VHS or SVHS and "WITH GAPs" it´ll have A/V desynch.

Ideas ?

[mkanel]

@Adalancas

After reading your post I took another look at VirtualVCR and found that I had the wrong video standard set. It now works quite well for me, I apologize to VVCR for saying it didn't work for me.

There are probably hundreds of things that could cause one successful capture while others failed. Here's a couple of ideas:

1) Your 8mm player might put out a much more accurate framerate.

2) Like me you accidentally changed a capture setting.

3) The 8mm player might be of a different standard. I see Brasil is a PAL-M country. Is the 8mm player from somewhere else with a different standard?

Here are the settings I used in VVCR. Framerate=29.97 (NTSC standard),video device setting=NTSC_M, uncompressed audio, resample audio box checked and resample audio dynamically selected, Adjust stream offset checked and sync using streams offset selected. I'm using the sourceforge WDM drivers mentioned in my first post.

Once again good luck. Mike.

[ADLANCAS]

@mkanel
1) Your 8mm player might put out a much more accurate framerate.It can be. I used a Sony Handicam.
2) Like me you accidentally changed a capture setting.
I changed ?:confused:
No, everything is the same as before.
3) The 8mm player might be of a different standard. I see Brasil is a PAL-M country. Is the 8mm player from somewhere else with a different standard?
8mm Player is NTSC.

Until now I can´t get a conclusion about this thema.

Thanks,

Alexandre

PS.: Adalancas :eek:

[mkanel]

@Adlancas

Sorry about the misspelling:(

Just to be clear, the 8mm is NTSC, are the othrs PAL?
If so in settings, video tab, I assume you changed the frame rate to 29.97. Also under the video tab did you select "Device settings" and change that to PAL?

Mike.

[ADLANCAS]

8mm is NTSC.
Others can be NTSC or PAL-M (I can handle both and frame rate is the same, it means 29.97)

In Device settings must be selected Pal-M when it's necessary.

I hope that is clear now.
Thanks,

Alexandre