Question about interlacing problem

[phinsman]

Well here's what I did:

1. Captured at 720X480 with Virtual VCR, filtering out the bottom 8 pixels which are always noise with my card.
2. Used VirtualDub to edit out commercials. Resized to 352X480.
3. Resaved the video to several new files. I did it this way to help me with batch conversion.
4. Used CCE to convert to Half-D1, VBR.

Outcome:
Looked great on the PC. When I tried it on the TV it was like the interlace problem I had last week, when I had the fields backwards.

I tried switching the field order, but no change. I used TMPGenc, all sorts of combinations, but no change. Whatever field order I tried, or if I tried "Non-Interlaced" I had the same problem.

I went back into VirtualDub and frameserved the original source (720X480) to TMPGeng. It detected the source as "Non-Interlaced." Knowing this was bogus, I changed it to Interlaced, Top Field first, which is what is usually the case. This fixed the problem.

So...basically I don't get it. I've not had this kind of problem before with TMPGenc, and it seemed to be the 8-pixel filtering I did with Virtual VCR that caused the problem. But why?

Thanks to anyone who can explain this to me.

Dale

[Craig Tucker]

So...basically I don't get it. I've not had this kind of problem before with TMPGenc, and it seemed to be the 8-pixel filtering I did with Virtual VCR that caused the problem. But why?

Dont know why this caused the problem, but if you are playing it on your TV you would not notice the noise at the bottom anyway due to your
TV's overscan. So there is no need to crop it really.

[txpharoah]

Are you cropping the bottom or clipping (covering up) the bottom 8 pixels. I am aware that some software cannot crop with interlace. Though it should not be a problem, there is a defect in the software creating the problem.

As stated, no reason to remove the errors because of over-scanning, but post-processing filtering (of this sort) is always better than on-the-fly filtering. Since you capture AVI anyhow, then just do this in the MPEG conversion phase.

Again, clipping or cropping? Clipping (covering) is best in this case.

[phinsman]

Hello...

It's cropped in the capture program, because the source video is actually 720 X 432.

I didn't realize it wouldn't show on the TV. I'll give it a try without cropping.

Thanks,
Dale

[phinsman]

Hello again...

Just a follow-up, and one question.

I did everything over again without the cropping filter, but when I viewed the finished DVD on my TV I did see the noise at the bottom of the screen.

I'm curious about the clipping that txpharoah mentioned. Is there a VirtualDub filter which does this for you; perhaps Region Remove?

Thanks,
Dale

[txpharoah]

Look up "overscanning". You cannot see the edges of a picture on tv.
Clipping is a filter found in Premiere and TMPGenc.

[Umen Pich]

Amazing ! It's exactly my story. The difference is only that the raw material was ripped from a DVD and the MPEG encoding was done by TMPGENC. I tryed also all the combinations and got always the same jerky result. Finally I gave up, blaming the ripper (vstripe). Normally I use DVDDecripter.
Does anybody have an explanation ?

Well here's what I did:
1. Captured at 720X480 with Virtual VCR, filtering out the bottom 8 pixels which are always noise with my card.
2. Used VirtualDub to edit out commercials. Resized to 352X480.
3. Resaved the video to several new files. I did it this way to help me with batch conversion.
4. Used CCE to convert to Half-D1, VBR.
Outcome:
Looked great on the PC. When I tried it on the TV it was like the interlace problem I had last week, when I had the fields backwards.
I tried switching the field order, but no change. I used TMPGenc, all sorts of combinations, but no change. Whatever field order I tried, or if I tried "Non-Interlaced" I had the same problem.
Dale

[Vejita-sama]

Cropping interlaced source is always tricky, I wouldn't do it. Try making a short (2-5min) test clip:

1. Capture at ???x480
2. Have TMPGenc resize to 352x480, encode to MPEG2
3. Burn to -RW and play on standalone

[kees1952]

Phinsman,

I went back into VirtualDub and frameserved the original source (720X480) to TMPGeng. It detected the source as "Non-Interlaced."

Are you shure the captured source is interlaced ? In some codecs it is necessary to adjust it. (something like 2 fields if more then xxx lines)

When you see noise at the bottom of your TV-screen and it's a normal 3:4 TV set, there is something wrong. Do you also see it when playing a VHS video ?
It can be something in the vertical deflection ( amplitude, vertical position or linearity). It is also possible that you have a problem with the Anode voltage on the TV-tube (should be about 30 - 33 kV, keep away from it!!). In most TV sets this supply is not stabelized so in dark scenes, when the TV-tube has very little current this Anode supply will increase and give a smaller picture on the tube. In this way it is possible to see the part of the video with should normally be in the overscan. It is possible that the anode voltage is adjusted too high. If you are in doubt, consult a technician.

Regards, Kees Janssen.

[phinsman]

Kees,

I am almost certain the source was interlaced because I captured it from VHS.

As far as the TV goes, I don't see noise at the bottom when playing VHS, or watching regular TV.

Thanks,
Dale

[DJRumpy]

You should be able to safely crop an interlaced source. Just be sure to ALWAYS crop in even values if your cropping from the top. If your source is from VHS, you should also see if your capture is telecined. If it is, you can convert it back to progressive by using a filter.

Your capture card may be 'seeing' the noise during capture. Your VCR playback also chops off playback area due to overscan, which normally hides this head noise. Many VCR captures show head noise at the bottom, and towards the right. Yours is cropping WAY to much though. The captured vertical should be 480. Yours is chopping your captured vertical to 432. Change your settings to turn it off, or reduce the amount it's cropping. It's no wonder you could see almost 50 vertical lines missing. Normally you wouldn't chop off more than 32 or so.

If you must crop your vertical for 432 (for some reason), and your seeing the black area when you encode, then just resize your video back to it's the fullscreen resolution for the format your encoding to (i.e if your encoding to CVD (352x480), then resize the vertical to 480. It may appear just the tiniest bit tall, but chances are you won't notice such a small change in aspect. Again, reduce the amount your cropping. It's way to much. Set it close to the 8 lines of noise your trying to remove.

As an alternative, rather than cropping those bottom 8 lines though, you can also simply matte them to black (basically just overlays them with the color black), so they do not use up bitrate due to noise). Virtualdub doesn't come with a filter to do this, but you should be able to find one. AVISynth will do it out of the box.