TV Capture Suggestions

originalsnuffy wrote on 5/22/2003, 10:40 AM
I'm trying to come up with a workable scheme for TV capture using the ATI TV Wonder card (PCI). I realize this isn't the best card available, but this is a low volume application. I have the latest version of ATI MMC installed (7.9) that supports this card.

The highest quality captures seem to be with Vegas Video 3.0c directly, but this seems to create fairly large files before editing, and importantly requires direct intervention to start and end a capture. I have heard that there are macro programs that can help here (any thoughts?).

I have a fair amount of software available beyond Vegas Video for editing (mainly low end editors that I purchased before Vegas Video 3.0). Are any other packages better for capturing? I didn't really like the quality of the captures using ATI software, but could use it I also have another digital vcr capture program, but it seems to capture with real time MPEG 2 compression that drops frames.

Dropping frames causes problems with vegas video, as we all know. The sound and video and synch quickly get our of what when doing MPEG2 conversion for creating DVDs.

Another work around might be to convert to avi using programs that insert frames to keep sync. It looks like tmpgenc might do this, but I haven't figured out how to do this and keep the picture in the correct aspect ratio. I'm open to suggestions how to edit the mpeg2 files that I have without losing synch.

Thanks!

Comments

discdude wrote on 5/22/2003, 10:58 AM
Max resolution when capturing using ATI's MMC is 640x240. This is why MMC looks bad.

I believe that Vidcap captures uncompressed RGB24 by default. This, as you noticed, wastes a lot of hard drive space (especially considering that the TV Wonder is kicking out 16 bit YUY2).

If you want max quality, I would capture using HuffYUV and a capture app like iuVCR (http://www.iulabs.com). You can use VirtualVCR (http://www.digtv.ws), which is free unlike iuVCR, but VirtualVCR doesn't have any scheduling features AFAIK.

I don't know how to easily fix sync problems with MPEG2 but VirtualDub (http://www.virtualdub.org) helps with AVI files.
Angel01 wrote on 5/22/2003, 10:59 AM
for capture i would recommend using iulab's iuvcr as it bypasses windows limitations.
u can choose the realtime codec, and my choice is the free huffyuv which is lossless.
using that codec u will be able to capture full format 720 x 576 (or 480 for ntsc), whithout dropping frames
mikkie wrote on 5/22/2003, 11:37 AM
Thanks for posting the link to the iuvcr app - wasn't aware of it...

FWIW, would suggest the trial app unless someone has experience with the ATI TV Wonder card capturing at full frame size - not sure if the reduced size is a hardware limitation or not, ie: if the iuvcr app simply uprezes the picture rather then capturing the larger frame size assuming full frame capture is possible.

Otherwise might try capture at 320 x 240 and see how that works for you versus the odd max size, or any other combo of size and conversion to see what gives the best result. It's possible that the ATI software might be the best bet depending on the level of hardware specific optimization - I know the mmc stuff does get more from their aiw series then other, 3rd party apps. A lot of folks use VirtualDub with no prob., & there's AVI_IO, & freevcr. Vegas is optimized for DV capture, so I wouldn't recomend it.

Dropping frames is almost expected if you are capturing RGB using VFW. As posted, HUFFYUV is a good choice, or you can use picvideo or morgan etc. Mpg2 capture is also a decent option, preferably set to all I frames for editing - what I would reccomend if using the mmc software.

One option might be to check this out: http://www.pcmicrostore.com/part-detail.asp?id=409254

"convert to avi using programs that insert frames to keep sync."

This is usually done during capture, because the audio and video clocks differ - shouldn't really be much of an issue with a current PC. If you video is out of sync on capture, it's probably related to capturing rgb and dropping frames - the system can't keep up getting the video on the drive... If everything seems cool until render to mpg2, an old fix in any editor is to split the tracks periodically on the timeline to force sync at those points.

Another possibility is if you have different audio and video track lengths - the audio will be out of sync towards the end of your proj. This can usually be handled well by stretching (control + drag) the audio track to match your video track length - if you audio track is split, you'd want to render audio only to wav, then import to another track muting the original as you'd want to stretch the entire audio track.


discdude wrote on 5/22/2003, 12:23 PM
OK, quick lesson. NTSC video is interlaced - basically each frame is broken into two parts called fields. So a 480 line frame is actually comprised of 2 240 line fields.

Moving on - ATI's TV Wonder is powered by a bt878 video encoding chip. The bt878 can transmit two fields across the bus at a time.

Therefore you can:

1) Send one field to the hard disk (capture) and the other field to the overlay. That is the method used by the ATI MMC. That is why the max resolution is 640x240.

2) Send both fields to the hard disk and use a "software" method of previewing the video. This is the method used by iuVCR and VirtualVCR. Just make sure you have the Smart Tee Sink-to-Sink preview turned on. Yes, CPU usage is higher in this case, but with today's powerful processors, this is becoming less of an issue.

A final note. VirtualDub, AVI_IO, and Freevcr are all VFW capture apps. They don't mix well with the WDM Tv Wonder drivers which use a DirectShow interface. In order for the VFW apps to work, the VFW calls have to be translated to DirectShow calls through the use of a wrapper. For some reason, resolution through the wrapper is limited to one field only.
mikkie wrote on 5/22/2003, 12:39 PM
Wasn't at all sure on the TV wonder, what chip/implementation it used - glad you had the info on that as those cards seem an oddball of sorts - least comparred to the aiw cards and other bt based cards...

Strange as the VFW apps limit it to one field... know it doesn't effect quite a few other wdm driver based analog caoture hardware. Oddball I guess sums it up IMO...

jetdv wrote on 5/22/2003, 1:05 PM
For the BEST capture, run the TV signal to a camera/convertor/deck that can do pass-thru and record it as a DV-AVI via firewire. This would solve ALL of your resolution problems.
BrianStanding wrote on 5/22/2003, 2:40 PM
Or just record to DV tape through your camera or deck's analog inputs.

Analog = the universal digital standard.
originalsnuffy wrote on 5/22/2003, 2:46 PM
These are great posts, thanks! I'll experiment with iuVCR and VirtualVCR for captures.

In terms of fixing the already "corrupt" MPEG2 files, it does make sense that I could expand the audio and get close to matching the video. But re-rendering to an AVI with a program that inserts missing frames when necessary would be most accurate. Which software options make the most sense for this specific fix (hopefully I will only have to do this with files that are already captured as other suggestions should fix the problem in an on-going fashion).