From AVI to DVD - Upper or Lower Field First problem

[sanlyn]

That's weird. I didn't see anything wrong with the size of the TMPgenc clip either.

[FrankDrebin]

I've just had one of these moments:


This evening I'll try doing a test. If it works, I'll let you know why both fields are displayed at the same time. Let's keep our fingers crossed!

[jagabo]

It occurred to me that you might be confusing the comb artifacts due to time base errors with the comb artifacts due to motion. In this 4x enlargement of a portion of the frame:



The comb artifacts around the guys head are mostly due to his motion. The smaller comb artifacts on the door frame in the background are due to time base errors. The DVD player or TB may not fully remove the combing caused by time base errors, depending on what deinterlacing algorithm is used.

[FrankDrebin]

It occurred to me that you might be confusing the comb artifacts due to time base errors with the comb artifacts due to motion. In this 4x enlargement of a portion of the frame:


[Attachment 19314 - Click to enlarge]

The comb artifacts around the guys head are mostly due to his motion. The smaller comb artifacts on the door frame in the background are due to time base errors. The DVD player or TB may not fully remove the combing caused by time base errors, depending on what deinterlacing algorithm is used.

Thanks for clarifying that. Here's what I noticed: the TerraTec device I'm using is now no longer supported. It was supposed to work under Windows XP all the way to Windows Vista. I did another VHS capture, a couple of weeks ago, on an old laptop I've got here which runs under Windows XP. I don't know if this is a coincidence or not, but I tried converting it in MPEG-2 via TMPGEnc (it still detects "Lower Field First", but doing the deinterlacing filter test I described in my first post, proved that I had to change the field order to Upper First in order to avoid stuttering). Anyway, I tried playing this MPEG-2 file on the tv screen and, guess what: no interlaced areas at all!
On the other hand, I've done the latest captures on a PC running under Windows 7. Again, it may mean nothing, but all of the captures done under that operating system are causing me trouble. Later today I'll try capturing a video sample of the sit-com on the old laptop featuring Windows XP and I'll let you know the results.

Maybe the "auto field detection" thing doesn't work properly on the capturing device on the newer, unsupported operating systems?

[DB83]

Eliminate all possibilities and do a brand new capture - not as mjpeg - on the current PC. I really do not think this is an OS issue. If it was then the device simply would not work.

[sanlyn]

Interlaced video viewed on tv has been deinterlaced. The PC is by nature a progressive display medium that does not deinterlace or manipulate pulldown (telecine). VirtualDub does not dinterlace, but many media players do: VLC deinterlaces only if you set it to do so, while MediaPlayer and players like MPC-BE treat interlaced/telecined video in much the same way your tv does.

Many capture devices do not do a clean job of interlacing during capture. Many are just noisy, with no way around it. Capturing to lossy encodes, even at high bitrates, makes those problems more difficult to work with. And as jagabo explained, tape playback has many timing errors depending on the player. I generally capture VHS using older VCR's from the mid-1990's that seem to have more robust mechanisms, better tracking, and less problematic output than newer players, the quality of which deteriorated significantly in the late 1990's and later. I also found that newer high-end tbc-equipped players have more difficulty tracking badly damaged tapes. I use a couple of DVD recorders for tbc pass-thru; that isn't a perfect solution, but it sure beats having nothing to help with those errors. There are Avisynth plugins that can help alleviate combing artifacts, and which can smooth lines and edges (to a certain extent, and within definite limits). There are no filters that can repair the noise of wiggly lines or compression artifacts that smear motion and distort edges. For those, one needs a better player and better capturing and encoding.

There are some elements of tape or film damage that can't be repaired except with professional gear and programming skills. I think you know the cost factors involved. And even the pros find stuff that can't be fixed.

[FrankDrebin]

Ok guys, here are the results: trying to do a capture under Windows XP generated more or less the same results. The only difference I noticed is that the AVI files captured in this way, when processed with TMPGEnc, are Top Field First (according to the Deinterlacing test), instead of being Bottom Field First, as the ones I captured under Windows 7. As far as the final videos go, they still show those "interlaced" artifacts which jagabo identified as Time Base errors, just like the first videos I captured under Windows 7. But, here's the interesting part: I found that they aren't always visible.

Here's what I tried before: starting from the same sample clip I posted here in my first post, I generated two MPEG-2 files, one with Top Field First, the other with Bottom Field First. Remember: the sample clip is Bottom Field First. I then watched them on my computer using DVB Viewer:

- Top Field First: stuttering + Time Base errors.
- Lower Field First: no stuttering + Time Base errors.

I then tried opening the video with Cyberlink Power DVD: no more Time Base errors! They were gone!
I then checked back the DVB Viewer options and activated the Yadif deinterlacing algorithm: no more Time Base errors, again!

On VLC, instead, whichever deinterlacing algorithm is selected, those TB errors won't show.

I then watched both videos on one of my DVD players (connected to an old CRT tv) and, again, no Time Base errors!

The picture I shot today with the digital camera (it's in one of my previous posts) portrays the video being played on the PlayStation3 connected to a full HD tv. In that case, Time Base errors were visible.

Maybe the PlayStation 3 doesn't use a deinterlacing algorithm which can make those errors invisible? Maybe they will always be visible when the videos will be displayed on a LED, Full HD tv?

[DB83]

I read somewhere, don't remember where, that top-field gives best playback compatability.

I see no reason why you can not capture top-field with your PC (win7). In fact only when I do DV does it capture lower-field. Then I encode that with pro-coder and that insists encoding as top-field. Go figure.

[jagabo]

Maybe the PlayStation 3 doesn't use a deinterlacing algorithm which can make those errors invisible? Maybe they will always be visible when the videos will be displayed on a LED, Full HD tv?

Like I said, whether they are visible or not will depend on what type of deinterlacing is used. A dumb bob won't show them because you see only one field at a time. But a smart Bob might see them as picture detail. Because the comb artifacts aren't in motion, they stay the same over several frames.