Will DVcam pass-though give higher cap res than cap card?

[ahfairley]

I want transfer old 8mm videos to DVD. What I want to do is capture at 640 x 480, 24-bit color @ 30 fps, but with my current system the best I can do is about 480 x 320 at 30 fps without serious frame drop. I've tried the tweaks (disabling other devices, no programs running in background, separate capture disk. I've tried two cards so far, old STB tv card (BT848 chip), and Osprey 200 capture card (BT878 chip).

I'll probably get a DVcam later in the year. Can I expect better capture results using the DVcam analog pass-though to firewire? Or is the bottleneck not in the capture card but somewhere else in my system?

Thanks,

Alan

P.S. Please no comments about how I don't need to capture at 640x480 etc -- I've already determined the method I'll use, and am looking for the hardware solution.

[House de Kris]

With a miniDV camcorder, you'll get 720x480 only (assuming NTSC as your quere implies). Depending upon your hard disc, you will probably get very few dropped frames, if any. Your files will always be a bit over 200M/minute, or about 13G/hour. The quality will be stunning compared to what you've used so far.

[ahfairley]

Thanks, for the reply, House. I want to make sure you're talking about capping pass-through from an analog cam plugged into the DVcam, not capping DVcam tapes, though.
Alan

[yg1968]

I had similar capturing problems until I bought a Sony miniDV camcorder. The image is very good with a miniDV camera. Make sure to buy a camcorder that has a video in with a passthrough feature (most Sony DV camcorders do). Sony camcorders also defeat macrovision. DV will encode at 720x480.

With a miniDV camcorder, the camcorder is the capturing device, so the speed of your computer and hard discs become less important as the firewire port is only used to transfer the DV file to your computer. However, a DV avi file will require around 12 gig per hour of hard disk space unless you have a software authoring program that can convert to mpeg-2 in real-time (which is not recommended if you want optimal results for DVD quality).

Color is not RGB (4:4:4) but is compressed into something which is supposed to be equivalent to the human eye, called YIQ (down sampled to 4:1:1 for NTSC or 4:2:0 for Pal). These links will give you a better answer on these questions that I can give you.

The passthrough feature converts your analog signal into a DV signal. Sony calls it the analog to digital conversion feature. Obviously, this will not really improve the resolution of your video if your source is less than 720x480.

http://www.adamwilt.com/DV-tech.html
http://www.rtproductions.net/home/documents/DVCAM.htm
http://www.rtproductions.net/home/documents/Executive%20Summary.htm

Hope this helps,

YG

[mpb]

I want transfer old 8mm videos to DVD. What I want to do is capture at 640 x 480, 24-bit color @ 30 fps, but with my current system the best I can do is about 480 x 320 at 30 fps without serious frame drop. I've tried the tweaks (disabling other devices, no programs running in background, separate capture disk. I've tried two cards so far, old STB tv card (BT848 chip), and Osprey 200 capture card (BT878 chip).

I'll probably get a DVcam later in the year. Can I expect better capture results using the DVcam analog pass-though to firewire? Or is the bottleneck not in the capture card but somewhere else in my system?

P.S. Please no comments about how I don't need to capture at 640x480 etc -- I've already determined the method I'll use, and am looking for the hardware solution.

Well, OK, I won't comment except to say that 640x480 is all wrong for archiving... it's a VGA resolution, not an NTSC one. You want 704x480 if you plan to put essentially the same image on a DVD at some point. DV-cam obviates the matter by capping at 720x480, which is even better.

But as to your question... the main advantage of DV-capping is you get a time-base corrector. If your 8mm tapes are in splendid shape, just use a capture card. If they are getting on in years, use the DV-cam passthru.

To avoid framedrop, well, the solution is different for everyone. In many cases it's just a matter of adding sheer power to the system... i.e. CPU and RAM upgrades. I can cap with an ATI AIW on a P4 1.8ghz with no frames dropped in any resolution, so you may want to use that as a benchmark for your own system experimentation. If your box is faster than mine, and many are, then your capture card might just not be up to snuff. For reference, I capture in Virtualdub, completely in software, to uncompressed (or huffy) AVI. I can capture straight to Divx5, but doing it on the fly makes a more grainy output file than compressing afterward.

[HOOKEDONTECH]

expect to get great video and great audio quality. ive been capturing music videos on vhs from a svhs vcr and also music videos from cable tv and using a sony dv minicam trv 11's pass through function.
for software i'm currently using ulead 5.0.
it was necessary for me to select the device control in ulead to "none" for it to work properly or else the software tries to play the dv tape when i try to start capturing.
pinnacle studio 7 does not appear to let us disable the device control or i would be using it cause it seams to encode to vcd or svcd with better quality

[yg1968]

mpb,

Can you expand on what a time corrector does to improve image quality of old tapes? And how do you know whether you have a good time correcter on your miniDV camcorder? I am curious to know.

Thanks,

YG

[mpb]

mpb,

Can you expand on what a time corrector does to improve image quality of old tapes? And how do you whether you have a good time correcter on your miniDV camcorder? I am curious to know.

Thanks,

YG

I'm playing with a borrowed Sony TRV-25 minicam, and I'm about 99% sure I'm gonna buy my own before much longer.

The time-base corrector is ESSENTIAL for dealing with older tapes, damaged tapes, or macrovision'ed tapes (such as commercial ones). There is a good reason, which I'll explain.

What you and I see on our monitors as legible video frames are not always thus. Many tapes begin to deteriorate and they actually lose frame integrity over time. Your TV will not show any ill effects because when it scans, it just keeps going in analog mode when a frame is corrupt, so we never visually perceive the problem. The TV just ignores it entirely.

However, feed an older or damaged tape into a capture card, and it's a whole new story. You WILL see flagging, flicker, dropped frames (because a frame is literally not there, not because your hardware couldn't handle it), and distortion. Also, analog videotape doesn't always feed frames at the correct 29.970 frames per second, due to tape stretching and decay. Sync problems can creep into the mix. It's pretty much bad all around. The digital eyes of that capture card can and will see every effect of the tape's deterioration. Since tapes tend to decay quickly over time, especially cheaper brands, you may see a lot of this with your capture card, depending. I use an ATI, as I said, and I get this problem on a lot of tapes I have made in 1994-5 or earlier, roughly.

A time-base corrector, which is built in to DV-cams with the A/V passthrough, manually corrects this problem in a digital sense. When it gets a corrupt frame, it feeds the previous frame again. It rations out the frames so as to feed them at EXACTLY 29.970 fps and locks the audio stream on with the correct timecode. It makes it a lot easier to deal with the deinterlacing... that part could be explained in its own article, so suffice it to say you'll be happy about it. Essentially, a TBC will take a damaged and uncapturable tape and "frameserve" it to your computer, in the best condition physically possible.

You can get stand-alone TBC's for a couple hundred bucks on the web, but the better bang for your buck is to just buy a DV-cam with A/V passthru. It's only a few hundred more and you get a camcorder that way in addition to the TBC. The Sony camcorder I am borrowing and plan to buy tends to close in the $550-650 range on ebay, which is just fantastic.

Essentially, this lets you cap VHS at 720x480 reliably. It's true that VHS only has enough information per frame to produce an interpreted resolution of about 352x240, but it's not a problem... you can always encode down, or on SVHS tapes or laserdiscs, you may well like it just the way it is.

For television, I just capture with the ATI and get perfect results every time, since broadcast signals are easy that way. I should write a guide... the method I've been using for a while now is working fairly well, and takes full advantage of the various software we use here.

Enjoy!!!

[yg1968]

Thanks for the explanation. I have the same Sony miniDV (TRV 25) camcorder. I am happy with it also. The TRV 18, 25 and 27 are very similar miniDV camcorders.