Faulty TBC issue? AVT-8710 insert frames?
 

Hi All

I've just received an AVT-8710. I've heard about some problems with these units.

I have a Panasonic VCR, and I went in to the menu system to see what the TBC did to it.

I've attached the result. The background artifacts (darker horizontal and vertical bars) seem to be difference each time I close and bring up the menu.

Is this a faulty unit? Should I send it back?

Thanks

Occasionally I saw the shown effect over the years, perhaps once in 100 captures, solved by rebooting the unit and making certain the correct "system" setting (PAL, NTSC, etc) was lighted in the LED panels. If those procedures don't allow your unit to lock into the signal completely, you have a defective unit.

My unit also loose sync and stays locked now after about 10 minutes of use - I hope it's just an overheating issue as I left it on overnight.....

It's also inserting some light moving noise in to the picture (although you don't really notice it with the usual VHS noise)

I'm also getting "Inserted frames" in virtualdub from time to time - usually about 10 at a time every 30-45 mins or so.

I might have to send mine back...

You don't normally get a notice about inserted frames from Virtualdub unless you enable that feature in the capture timing options setup. http://www.digitalfaq.com/forum/vide...html#post45242

sample dialog setup of various settings from section 5 linked above (this one is normally for AIW AGP cards with an external tbc in circuit). There are different recommendations discussed for USB devices.
http://www.digitalfaq.com/forum/atta...capture-timing

Should I disable those top 2 options? In the link, it says I should avoid this by using a TBC (which I am, although it's currently faulty!), but I'm not sure I should still use these or not? I note that you say that even the best TBC will have a few errors.

Try a short capture with the options shown, then examine the results. All capture devices won't use exactly the same options, and some tapes will need special attention. I'm not up on which capture device or player you're using. By disabling most VDub options you'll be able to see how the TBC itself performs without VDub making adjustments. The options shown are what I use with an AVT-8710 and either the AIW 7500 or AIW 9600XT, also recommended for the AIW 9800. I use different options in Win7 for my Diamond VC500 USB, turning off all audio resync options.

Thanks, that's good advice :)

My VCR is a Panasonic NV-HS930 and my capture device is a Hauppauge USB-Live2.

I'd be grateful if you could explain to me why you think I am seeing Inserted frames? The thing is, is that if I simply re-play the tape, it will probably be fine the second time, so it's not a tape issue.

Do you think it's just the AVT being a little inaccurate with it's output signal timing, trigging Virtualdub's insert threshold (whatever that maybe) ?

I guess I should try without the AVT and see if the figures are worse/better...

BTW, call me crazy, but I think my AVT is working better (it hasn't locked up in 20 mins so far!) by placing is on a packet of frozen peas.... :D

Isn't that what you said in post #3?

But why am I seeing these on a random basis? At a scene that had some inserted frames, after simply rewinding and re-playing, it seems to be fine.

You should be rewinding anyway to tighten the windings in the feed reel for smoother feed across the video heads. That's been a stable trick for years. I'd also advise that you try some recommended settings from the settings guide to prevent certain problems mentioned in the section on timing options. Since you're suing a USB device, settings for a/v sync were also mentioned.

Since you think the AVT might be inserting frames (not likely), try what you suggested and leave it out of the circuit. If you do that but leave Virtualdub defaults enabled, you'll get inserted and/or dropped frames anyway more than likely because you're accepting what Virtualdub thinks is "perfect" a/v timing. What will give you perfect frame and field timing within accepted limits is a properly working tbc, not Virtualdub itself.

Sorry, perhaps I wasn't very clear in what I'm trying to say.

I don't think the AVT is inserting frames. By "seeing inserted frames", what I mean is that the inserted frames counter is increasing in VirtualDub, which leads to jumpy video at that moment when the counter increased.

What I am suspicious of, is that my AVT is faulty and causing a badly timed output sporadically, causing Virtualdub to insert frames. Why I am suspicious that it's the AVT (or something not tape related), is that I can't reproduce it by rewinding the tape a few seconds to try it again.

I'm assuming (and I could be wrong here) that with the inserted frames feature enabled in Virtualdub, this is an indicator of the quality of the signal coming from the AVT? If so, what are acceptable limits here?

What are the recommended settings for a USB device? I only see reference to your internal cards.

Thanks

As the documentation states in the link furnished, If you enable frame insertion or dropping frames to maintain a/v sync in VirtualDub, then inserted or dropped frames are an indication of what Virtualdub thinks of your incoming signal in terms of its own pre-set timing preferences, and not an indication of the absolute timing of the TBC's output. This information is contained in VirtualDub's own online capture help. If you don't want to disable the features that adjust frame rate by inserting extra frames or dropping them, and don't want to to try disconnecting your AVT, then I suppose you'll just have to keep guessing.

The setting differences for most USB devices are the audio re-sync features, which should be turned off. Most USB devices maintain their own audio sync. The two settings recommended specifically for USB audio sync are shwon in the image of the timing options dialog in the previous post:
- In the "resync mode" section, enable "Do not resync between audio and video streams"
- Below that section, disable the "correct video timing..." entry, and enable "Automatically disable resync when integrated audio/video capure is detected"

This is all correct. :congrats:

It's a simple matter of plastic color. Is the AVT-8710 green or black?
Green = good
Black = problems

See also: http://www.digitalfaq.com/forum/vcr-...-8710-doa.html

Comparing results with the AVT in and out of circuit is one way of checking for different effects. But considering the other problems, such as overheating, I'd say that his particular sample is a dud. If you can't find a good working sample, you can always try the pass-thru workaround with recommended devices -- not a perfect solution, but better than nothing and certainly better than a defective unit.

So, I removed the TBC.

To be clear, when I was using the TBC, in Virtualdub, I had the following:
Drop/Insert frames enabled
Sync audio to video by resampling the audio to a faster or slower rate enabled

When I removed the TBC, I also disabled Drop/Insert frames and also the Sync audio option. So I admit, this wasn't a fair test.

But, the audio is terribly out of sync by about 1-2 seconds. This only seems to happy on long video clips, but what's weird, is that it affects the footage at the start too. It seems that taking short captures is fine, even for the same footage at the start.

Am I going crazy, or is this expected without a TBC?

Is the tl'dr that without a TBC and/or letting virtual dub insert frames or resample the audio/video, there is no way to get an in-sync capture?

What is the theory here on why this is the case? Is it because that audio is always recorded (even "blank audio") whereas a choppy tape will not produce detectable frames by the catpure device, thus no video recorded - hence, the audio track is longer than the video track. Is that correct? If this is correct, I'm not sure this accounts for the footage at the start being out of sync also during long catpures.

LS - Do you have any of the green TBCs for sale? These black AVT devices are all I can seem to find here

Thanks

Yes, bad procedure, you introduced triple variables. ;)

It is. Lack of TBC causes many issues. Among them are dropped frames. Dropped frames are usually what create audio skewing. So what you're seeing is expected.

Just to be clear, audio is not stored in sync with video. There is always natural variances. VirtualDub always changes the kHz by tiny amounts to maintain sync. Other hardware and software usually does too, but just hides this fact from you. VirtualDub is transparent about many aspect of capture.

No, that's not correct.
Yes, you can get perfectly in-sync captures, I've done it for 15+ years now. :)

As per my replies above, no, not correct. :no2:

I have several DataVideos available, which can be better anyway. PM me.

Ok, then why does a non-TBC capture cause audio sync issues? I'm not aware of the theory here. I just assumed that a TBC would keep the frame rate constant, so that audio+video are close to being at the same rate (thus the same "length" as each other in the final output). My understanding, is that dropped frames implies shorter video length, with audio still being recorded, thus sync issues, no?

Also, how do you get an in-sync capture without using a TBC? That was my question :) Is it simply just enabling Virtualdub's audio sync features so that it changes the pitch?

Thanks

It doesn't always cause sync issues, but often does.

That's true -- if the tbc is working the way it's supposed to.

No. If the incoming frame rate is too fast to maintain the desired frame rate, dropped frames restore the correct playing time.This might cause audio sync issues, or might not. The audio may or may not be complying. It depends on how you've set up your timing options. In your case, your USB capture device is maintaining the correct audio rate, unless you direct VirtualDub to take over that function. That's why different timing options are set up for most USB devices than for other types of devices.

You shouldn't enable VDub's audio sync features if you're using that Live-2 USB device.

Without an external tbc or pass-thru device, you're taking a chance on wildly fluctuation frame rates, and thus possible loss of audio sync if audio timing doesn't match. The AVT doesn't maintain audio timing, it just maintains video timing (that is, if it's working correctly!). If tbc timing is off, and you direct VDub to insert or drop frames to maintain a close tolerance to the desired frame rate, you'll get dropped or inserted frames if the tbc is acting up.

This is the timing option setup I've used for my Diamond VC500 USB captures, in XP and Win7, with the AVT or a pass-thru device in circuit for frame sync and audio monitoring turned off elsewhere:
http://www.digitalfaq.com/forum/atta...1&d=1495654821

Thanks for your reply.

Those were the settings I used (without a TBC, albeit) and got very bad timing. I don't think my Live2 is maintaining audio+video sync.

I misspoke with what I said above regarding dropped frame. Let me ask my question again correctly:

My understanding, is that dropped frames from the Live2 (e.g. due to bad tape), with the inserted frames setting in Virtualdub disabled, implies shorter video length, with audio still being recorded at the wall-clock length, thus sync issues (audio is longer than video). Is that correct?

No surprise, if your tape player timing is fluctuating wildly enough.

Most USB devices cointrol audiop timing, not a/v sync. There is no frame tbc in the Live-2.

Now the point has gone from the AVT dropping frames to the Live-2 dropping frames. At this point you're working with what seems to be a dud TBC, which likely is the source of most of these problems. Frames are dropped or inserted (if the features are turned on) to correct frame timing. That would maintain a 29.97 or 25 fps frame rate. In itself that won't correct audio timing. You can't adjust frame timing with the Live-2.

It's also possible that your player's timing is off, which is what a tbc is supposed to correct -- that is, if the tbc works and is powerful enough. With the gear I've used for 15 years I never had a/v sync problems and never had to insert or drop frames, and I've watched an awful lot of captures in scrupulous, repetitious detail during years of restoration procedures from both good and bad tapes. The only time I had a/v sync problems was some years ago when I started a capture with the F5 key instead of F6.

Something in your capture chain is misbehaving. Have you considered something like an ES10 or ES15 for pass-thru and not use the dud AVT at all? Many people do it successfully (including myself). My practice with the ES10/ES15 is to connect both audio and video through the the unit and let the pass-thru manage both.

You could also have operating system inteference, which is equally possible. Two other popular capture software possibilities are VirtualVCR and AmarecTV.