Dropped frames in Virtual Dub from certain VHS tapes

[equinox]

Hey all,

I have a problem when capturing from a few commercial VHS tapes that i own. The tapes i have are all of the same show but are different episodes. When I try to capture from some of the tapes, i get lots of frames dropped (say, 50 a minute), in random places throughout the tapes. Not in any particular scenes though, just in random places. MY CPU useage is very low right through the capture, my hard drive dosn't work very hard, and it happens with all codecs and all resolutions. With most tapes that i have in the series though, i get about 1 frame drop per 45 minute episode, so its not my pc.

If it is problems with the tapes i captured off, will a video stabilizer help?

Thanx

<font size=-1>[ This Message was edited by: equinox on 2002-01-14 04:48:19 ]</font>

[garryward]

I have seen this has well. I got round it by putting it in to my tv then takeing the feed from that and now no more droped frames

[ballfam]

I had this kind of problem too with VDub. I think it might have something to do with how the data is buffered. VDub appears to buffer some chunk of the video (and you get no drops), and then try to write it to disk (which causes a glob of dropped frames in one hit). Anyway, I solved my problem by going to AV_IO (see the tools link on this site). Even on the videos without problems, AV_IO does a much better job, I'm getting about 1 drop per 10,000 frames now, but with VDub I was getting about 1 every 30 frames.

[dinesh]

If this happens randomly and with only some scenes this is because of VHS disturbances on the tape.
The method garryward described may work because the TV output does not directly reflect this VHS disturbance.

[Bstansbury]

Hi, I get the same kind of dropped groups of frames even when I'm using ATI capture in AVI mode. The VCR recored (ATI) says there are no dropped frames, however, when I view it later with WMP there are clearly some frames missing. It does a little better in MPEG.

I'm bringing in Video from my Canon 8mm camcorder and I expect that it has worse timing than a VCR. I saw a note somewhere else in this forum about "Time Base Correction" which in very high end professional gear is a mandatory requirement. In these lower cost VCR/camcorder products it is very obvious that the time base of the recording (or playback) can be off from 29.97 frames/sec. For our low end capability I don't thing any of us could afford a TBC unit.

However, it seems that pushing the video through a TV is dong about the same thing, re-sync the video to a good time base, and theby reducing the dropped frames. One last point that kind of destroys the argument I just put forward,.. I don't think that any of these devices can be that far off the time base to drop the number of frames that we see missing. I guarantee you that you can drop 5 frames a second and you will never see it. Have you ever seen PAL on a British TV (or in a LAB). You can't tell the difference in the video.

I suspect that while the TV pass through is helping, there is still something that is going on with large groups of dropped frames. In my pictures, I actually see people "Jump" around. Hopefully this will get fixed once I start capturing with Vdub.

Thanks for your info.

[ironwood321]

Perhaps the video levls to low? or the sync or black level. Some TBC allow you to adjust this.

[equinox]

I've just discovered something interesting. When I encode at 352 x 288, I get all those dropped frames, but when I encode at 352 x 287 (which my card supports) or below, I get hardly any dropped frames.

[equinox]

Oh, and i get the same thing on all the programs I've tried to capture the tape with, but I havnt tried AVI_IO yet, ill try it tonight.

[Chi8ng]

I got the same problem as equinox: lots of dropped frames at 352x288, but hardly any dropped frames at 352x284. I am using AVI_IO with Pinnacle StudioVCD capture card.

[Bstansbury]

This is a question for Equinox.

The dropped frame issue is very critical to a lot of people, including myself,.. as it is the last thing that is keeping me from making some good VCD's.

You said you get the dropped frames when you capture your VHS tapes, but when you pass it through your TV you don't get any dropped frames. So here are some key questions.

1. When you capture VHS was it from the Turner input on your card by playing the video tape? Or was it from the composite output of your VCR and RCA cable input to your capture card.

2. What kind of TV do you have that will allow you to pass video/audio through it and out of it. Most all TV's have coax inputs and composite inputs but no output,... unless it is a professional monitor.

My Video card has two types of input, coax to the Tuner and this can come from your VCR, and it has composite video and audio.

I get dropped frames regardless if I use the TV Tuner in and capture a TV program, of if I use composite inputs from my camcorder or from my VCR output.

I hope I'm wrong and you do have an answer that will work for all of us.

[equinox]

I get the dropped frames whenever i capture from that particular VHS tape through composite cables or through my card's tuner connected to the VCR through coaxial cable.

And as for what garryward suggested, I do have a TV that had RCA outputs, but its huge, and I aren't carrying it into my computer room. I might have to end up putting my pc on the floor in my lounge room next to my TV if all else fails.

[Bstansbury]

Sorry Equinox,.. I posted my last note and all the questions to you,...but the questions should have gone to "Garyward" (Sp). Anyway, since he didn't add any more replies to this topic,.. I'm not sure if we know what he did.

If you have a TV with outputs,.. it must be a very expensive one,.. like the one I have in my living room,..which as you indicated,... is too large to move into a den or a computer room.

Anyway, if tried all combination of TV cable input, VCR input, and my 8 mm VCR input. The best is the cable,.. and the next is the VCR,... and last for quality is the camcorder. However, if I copy the camcorder to the VCR, I get the same quality as any of my VHS tapes. The point is that no matter what we use, we loose some kind of quality as we depart from the source. We I worked with professional studio quality equipment, i.e. $30,000 tape drives, they record in D1 quality and that is the best you would ever see on any commmercial that you see on TV or Cable or Satillite. This is what they use to broadcast programs everywhere,.. and even the Sat people use them as source to compress to MPEG streams via up and down links.

I have some better news for all of you that have experience dropped frames and I will post it again on the capture forum as a separate note. They are not dropped frames. They are missing segments of data that didn't make it out of video buffers to the harddisk. What you see is missing data,.. and there is basically a still picture for several milliseconds until the congestion is clear and the data in the buffers begin to flow again. It is also not lack of processor performance. Many times you will see that you are getting the jerky output and your processor is only running at 35%???.

Here is what I have discovered,... and I give the thanks to several of the people on this forum who have made the suggestion before,... and a lot of us just didn't get around to following it. I also think I found the same suggestions listed in the help sections of the VirtualDub software.

The answer is,....set up you capture card to go,.. and before you go, shut down everything in your computer you can find,... and there are a lot of stuff still running in the background in windows that can cause all kinds of interrupts. I use both VirtualDub and MMC 7.5. I was having the "lost data" on just about everything I recorded. and when I went to the 360x240 AVI, both system would say there are no dropped frames,...but the output was still jerky. I have shut down the task bar for MMC 7.5, and taken every application off the task bar except sound. I also shut down my printer application (one is a printer/fax)
which I expect was generating some strange interrupts to Win ME. Once I have done this I can record just about any format up to 640x480 with out any dropped frame signals from either capture software and I don't see any blocked data on the output.

Before this I was beginning to tell myself that I really didn't have a fast enough system to do video capture. Now I know that what it takes is careful control and lots of tuning.

I hope this helps everyone that reads it. I now going to try and improve my system some more by looking at other things.

[equinox]

thanx for the info Bstansbury, and ur right, even when im not capturing the video, it appears missing frames on my pc screen in Overlay mode, just when I play it straight off the tape. Back to my first post, will any of this improve if i use a video stablilizer, or is using a TBC the only way it's gonna improve?

Thanx to everyone who's posted

[cruffino69]

equinox, I've run into similar problems, but not with tapes. I had a thread here a bit ago about frame drops and signal quality (can't link to it because the search function is disabled right now, sorry). My issue was with the tuner in the VCR, not with playing tapes. I solved my problem by changing VCR's, so maybe you can too. Besides, VCR's are *MUCH* easier to move than TV's.

[equinox]

I've tried different VCRs, and theres a bit of change (for the worse, coz the VCR that I was usin gin the first place is Professional quailty). But if it is the VCR's fault, why do I only get this problem on a couple of tapes I have and not on the others?

[garryward]

Hi Chaps
just rad whats being going on . Sorry for no input but I ve be away all week
Any way My TV Taht I use to help the VHS tape a long is an 18 year old JVC 7 system I use the rf cable to my Tv them take the comp video out and into my pc ( no scart its too old ) and ther we go no dropped frames .

[ironwood321]

Are you playing your tapes back into the machine on the same vcr you recorded them on? If you are not that would explain why you are dropping loads of frames. Are the vcr heads clean ie no oxide?

I have always seen the best copy produced from the vcr which the tape was recorded from. If I try some tape in another vcr I get very high dropped frames and bad interlace problems.