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Sections of Choppy Motion from TMPG

 
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cwk



Joined: 05 Jan 2004
Posts: 4

PostPosted: Mon 5 Jan 2004, 6:41    Post subject: Sections of Choppy Motion from TMPG Reply with quote

I wanted to edit a video that was stored on VHS tape and burn it to DVD. I digitized it using the Pinnacle capture card. I used Windows Movie Maker and Showbiz to edit and produce AVI files. I then encoded these files to be MPEG-2 DVD with Canopus ProCoder and TMPGEnc.

I tried two encoders because both have the same problem: Some parts of the video appear smooth and some parts have "choppy motion". I thought at first it was a field-order problem (e.g. I had selected odd-field first and it was really even). So I swapped the field-order. When I did this, the sections that appeared choppy before were now smooth, but the sections that appeared smooth are now choppy.

I have attempted to manipulate the settings within TMPGEnc like "Detect Scene Changes", various de-interlace settings, and IPB frame settings, without success.

One more thing: Showbiz can produce MPEG-2 files as well. Both the captured MPEG-2 file and the MPEG-2 file from Showbiz can be burned to disk. Their motion is fine. I cannot use them in the final project because they are either too big or un-edited. So it is not either the capture or the editing software. My problem appears to be with the encoder.

Any suggestions you may have would be greatly appreciated.
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RMN
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Joined: 04 Feb 2003
Posts: 587
Location: Lisboa, Portugal

PostPosted: Mon 5 Jan 2004, 19:00    Post subject: Reply with quote

The MPEG files you're exporting from Showbiz are all from the same source clip, correct (i.e., unedited)? I suspect that if you convert those source clips to directly to MPEG using TMPGEnc (or any other encoder), they wil also play fine.

The field order in MPEG files is really just a flag (i.e., a single value, set at the beginning of the file), so there's no way to make some sections "upper first" and some sections "lower first". In other words, the problem cannot be in the encoder (or it would afect all the footage).

I suspect the problem is some of the files were captured starting with the lower field and some starting with the upper field. This is a common problem in "consumer" formats such as VHS and Video-8. The card simply accepts the first scan as the dominant field, so there's a 50-50 chance of ending up with one order or the other (any video format can be captured with either field order, but mid- and high-end formats have sync signals that tell the capture hardware which order to use).

Think of it this way: the tape has the fields recorded in this order:

Frame1A Frame1B Frame2A Frame2B Frame3A Frame3B, etc.

The capture card, however, sees only this

Field1 Field2 Field3 Field4 Field5 Field6, etc.

In other words, it doesn't know which fields make up which frame (1 and 2 or 2 and 3, and so on). So the field order in the captured file depends on which field was being read when you pressed the "capture" button.

When you export the resulting (edited) file, some sections use a different field order from others (because that's how they were captured). But now the signal is regular (i.e., every field starts after the previous one ends), so the order is reversed in some sections. Look for a "reverse field dominance" filter in your editing software, and apply it to the clips that look wrong (or, if all else fails, use a deinterlace filter, although that will make you lose some resolution).

RMN
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cwk



Joined: 05 Jan 2004
Posts: 4

PostPosted: Wed 7 Jan 2004, 2:59    Post subject: Reply with quote

Thanks for your help RMN,

I have edited the clip within Showbiz -- to take out the commercials and whatnot -- but they are all from within the same capture session.

So, essentially, I have a single capture that flips between the 2 "field order dominance". As I cannot tell what sections are "flipped" until I encode it into MPEG-2, is there software available that will tell me this? split the file where the field dominance flips? Or, are there capture cards that are smart enought to figure this out?
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RMN
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Joined: 04 Feb 2003
Posts: 587
Location: Lisboa, Portugal

PostPosted: Thu 8 Jan 2004, 19:57    Post subject: Reply with quote

When you say "from the same capture session", do you mean you captured everything to a single file and then cut it (after it was captured), or that you captured it to several files? If it's all to a single file, it should all have the same field order. Which would mean that Showbiz was the one reversing the field order. I've never used it, but I find that almost impossible. Do you have any other editing programs? If you don't, you can download some for free (ex., Wax) Try making a few small tests (use DVD-RW discs so you can re-use them) to determine where, exactly, the problem is being introduced.

As to cards that will correct the signal, yes, I suspect the more expensive analog cards will do that, but it's probably easier to simply copy the VHS tape(s) to DV and then capture from DV. If you or one of your friends have a DV recorder / camcorder, this would probably be the easiest way to do it. DV recorders usually correct the signal timing from analog inputs. This can cause some corrupted frames (where the correction was made), but you can get rid of those easily during editing.

RMN
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cwk



Joined: 05 Jan 2004
Posts: 4

PostPosted: Sat 10 Jan 2004, 5:56    Post subject: Reply with quote

Yup,

All the video is from the same clip. I have tried using MovieMaker2 and Showbiz with the input video (Adaptec creates mpeg-2 files, I had said that I used Pinnacle earlier, my mistake) and encoded both of the resulting avi files with TMPG and Canopus. All combinations have the same error. This shows up with multiple source videos. I will attempt to find a different editor, and let you know what I find.

ck
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RMN
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PostPosted: Sat 10 Jan 2004, 18:43    Post subject: Reply with quote

If you're capturing directly to MPEG-2, then why are you recompressing the files in TMPGEnc or ProCoder...?

RMN
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cwk



Joined: 05 Jan 2004
Posts: 4

PostPosted: Sun 11 Jan 2004, 17:55    Post subject: Reply with quote

The MPEG captures have commercials and other footage that I would like to trim from the finished product. I don't know of a way to edit the capture without ultimately re-compressing it.

There are two sources that I am working with. One is a DVD and the other is VHS. I am capturing the VHS tape into MPEG-2 using my Adaptec card. I was looking to use either MovieMaker or Showbiz as my editor because I am new to the game and both are fairly easy to use.

Thanks for your earlier suggestion about the editor being the problem. Both Showbiz and MovieMaker were flipping the field order at various points. Interestingly, both editors were doing this at the same points!!

Based on your suggestion, I converted both the DVD and the MPEG file into AVI using DVD2AVI w/the Huffyuv 2.1.1 codec. From here I can now use Premiere to do the editing (Premiere is way too slow in rendering when attempting to edit MPEG-2 files). Premiere is handling these transition areas correctly!!!!

Is there a way I can edit the MPEG-2 capture without re-compressing??? Or, can I tell my Adaptec card to capture in AVI instead?? I have been looking through the documentation on it -- which is pretty weak, by the way -- and I haven't found a way to do this.

Thanks for your help!!
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RMN
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Joined: 04 Feb 2003
Posts: 587
Location: Lisboa, Portugal

PostPosted: Mon 12 Jan 2004, 5:53    Post subject: Reply with quote

I don't know which card you're using (Adaptec makes several models).

There are some programs that can edit MPEG-2 files without recompressing (well, the areas around the cuts always need to be recompressed, but the rest can be left untouched). Even Premiere can do it, but I think only with an AVI "wrapper" (i.e., the files are AVIs but the codec keeps the data inside those files in MPEG-2, and knows when to recompress). Maybe Premiere 7 (Pro) can handle MPEG files directly; I haven't really used it much yet (doesn't run on Windows 2000 and all my editing systems are running W2K).

If the card really is MPEG-2 only, then the programs that came with it should be able to edit in MPEG-2 without recompressing. Should. Doesn't mean they actually do. Confused

RMN
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