Frame dropping due to video input quality

[cruffino69]

Ok, I've seen a few posts here where people have experienced frame drops due to variations of the input signal (e.g. two different VHS tapes, one works well, the other doesn't). Has anyone verified this to be a real or perceived problem?

My feelings (without knowing the intimate details of the video capture process across hardware/software) is that it's real.

Is there hardware out there that is more or less immune to this type of problem?

Here's my situation:
I have an ATI Radeon 64DDR ViVo and am trying to capture 1 hour of broadcast TV (I use an old VCR as a tuner) directly to VCD-compatible MPEG-1 (we all know that's not exactly the truth). My system can easily handle it; only about 20% of the CPU is occupied with the capture task.

I stop running everything I can (antivirus, etc.) during the captures. Even so, every once in a while I'll have dropped frames reported. Entire shows will be free of drops, others will have just a few clustered together, still others will have several places with drops.

Why is this bothersome? With the ATI MPEG-1 captures, you need to demux/mux the file with TMPGEnc (or equivalent) to get it to be truly VCD compliant. After doing this with an MPEG that has frame drops, the audio will be out of sync after the point at which the frame drops occur. It only takes a few to become noticable, and only a few more after that to become annoying, and only a few more after THAT to become useless. Consider 1 hour's worth of video. That's 107892 frames. If you drop 15 frames, that will give you .5 seconds of audio desynchronization. 15 frames is only .01%.

By the way, most MPEG editors can't handle the dropped frames and generate an output equivalent to the demux/remux done for VCD compliancy.

In the past, I've captured 2 hour segments of video without a hitch. What's the difference? Aside from some driver updates and a hardware change from a SB Live! Value to a Turtle Beach Santa Cruz, the source of the video was an 8mm camcorder instead of the VCR I now use.

Why am I focused on the video input quality instead of these other things in my setup? There is no pattern to the frame drops. All these things in the computer, at least to me, should give some kind of repeatable pattern. That and intuition now that I see that other people have had similar problems.

I'm going to run some tests to see if I can verify this as a real problem. I have a different (newer) VCR that I'll be using to drive video into the Radeon. If I can capture several ( 6-8 ) hours of video using this setup without dropping frames, then I'll be convinced it's a signal quality issue.

If not, I might have a Radeon 64DDR ViVo that someone can pick up cheap

<font size=-1>[ This Message was edited by: cruffino69 on 2001-11-30 13:54:52 ]</font>

[Anonymous65]

The problem with frame drops due to poor video is only fixable by using a Time Base Corrector, a full frame memory device that inserts new vertical sync pulses where the original is gone due to noise or other VCR playback problems. When the capture card cannot detect a vertical sync pulse, it will drop it and wait for the next frame.

[cruffino69]

I wanted to wait a while before reporting back to make sure I wasn't jumping the gun. But as far as I'm concerned, I have answer my question.

Using the newer/higher quality VCR I've been able to capture over 12 hours of video without a single frame drop.

So, if you're set up like I am and experiencing random frame drops, be suspicious of your video source.

[marvin the martian]

read your post,very interesting.
do you think some of the frame dropping could be due to the fact that when the computer flushes out the windows swap file,it causes it to start dropping frames from that point.
mines only seems to start dropping frames the minute the swap file is being flushed out
how do you turn this of

help appreciated

[dirk67]

I also have this problem, but only with 2. generation copies. I get up to 30% dropped frames, the output, while still in sync with the audio (thanks to VirtualDub), is useless. With 1st generation tapes, I get maybe 1 dropped frame every 1500 frames, that's less than 0.1%.

[cruffino69]

Marvin, I suspected that it might be a swap or memory cleanup issue, which is why I made sure everything was turned off (hopefully Windows would clean up before the capture started). I even made sure to reboot. None of this had a major impact on the frame drops.

I think you can get a tool that forces Windows to clean up memory; I've never tried any of them.

Good luck though!

Just as an added bit of information. I tried to "simulate" a bad composite signal by changing channels, unplugging the video cable and powering down during capture. None of these events caused a single frame to drop! So I guess that the Rage Theatre chip is built to handle major catastrophes but not subtle disruptions.

[Greg12]

fragmented HDD?

[ngnr]

cruffino69, I have the same video card and have experienced the same problem with drops and ended up by fixing it the same way as you did. In captures with my old video 8 cam I would get periods where I would have no drops and then all of a sudden, 7 or 8 drops, sometimes lots more. I tried everything I could think of, including getting a good defragger but nothing seemed to make any difference. Until I got a new cam. Now I can capture the exact same tapes with 0 drops.

I read somewhere on here that it has to do with some synchronization signal on the tape (in my case probably some weak hardware not reading the signal properly) but I'm not sure exactly what the full explanation was.