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Old August 26th, 2015, 08:37 AM   #1
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Mysterious lagging experiement

Have a VHS tape in my project that I was working with and re-digitized on nicer hardware (ADVC-300). Rendered using mpeg2, same bitrate as original file, same file size, same hard drive.

Now, when I load it into vegas it causes serious lag whenever I'm viewing/editing it. I did the same thing with another tape, no lag.

Any ideas? I've re-rendered again, made sure audio bitrate is same, no dice. What the heck?
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Old August 26th, 2015, 12:29 PM   #2
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Re: Mysterious lagging experiement

Sorry I don't have direct answer for your question. What codec are your captures from the ADVC?

MPEG2 is not a very good capture, editing, or intermediate codec at low bitrates. It's a delivery codec for DVD (note there are other flavors of MPEG2 for other purposes).

I'd suggest that you capture from the ADVC-300 in DV, a standard def codec with mild compression that is an excellent performer for capture, editing, intermediates, and mastering in standard def.

Only go to MPEG2 for distribution...
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Old August 26th, 2015, 02:26 PM   #3
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Re: Mysterious lagging experiement

Seth knows what he is talking about.

Mpeg2 is no good for editing, it's the worst.
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Old August 26th, 2015, 03:54 PM   #4
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Re: Mysterious lagging experiement

Quote:
Originally Posted by Seth Bloombaum View Post

I'd suggest that you capture from the ADVC-300 in DV, a standard def codec with mild compression that is an excellent performer for capture, editing, intermediates, and mastering in standard def.
They are already in mpg....and I don't want to recapture all 20 tapes. Can I re-render them to something else more manageable in vegas? I just tried wmv, I'll see if that lags the same
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Old August 26th, 2015, 04:27 PM   #5
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Re: Mysterious lagging experiement

Seth knows more than I do, but that being said, the problem is that no matter how you render it's going to lag because mpeg 2 is a delivery format and it doesn't play well with editing programs. I forget the reason that is so.

To clarify, when you say lag, do you mean the audio and video are out of sync when playing in Vegas? If not, what exactly do you mean by lag?

At any rate, you should have converted the VHS tapes into a DV codec, not mpeg 2 as Seth said. That doesn't help you now, I know.
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Old August 26th, 2015, 05:55 PM   #6
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Re: Mysterious lagging experiement

Sorry you're 20 tapes down the road. Ouch, I can sympathize, I suspect many here can. This discussion really is about workflow...

Well, you certainly can render to a better editing codec - Sony's version of DV (aka. DV25) in standard definition is excellent.

If it were me, I'd do some quick tests, then compare to a new DV capture. Only you can decide if any visible quality differences justify recapturing. Be sure to include samples of any high-motion content in such a test. Quick tests before batching lots of content! That will also determine that any lag you're seeing with the MPEG2s is actually fixed.

OTOH, WMV, though a distribution codec... well, Vegas cuts through it like butta' in most cases. If you have a high enough bitrate to preserve quality, good WMV doesn't slow Vegas down. Maybe because it's integrated in Windows. If your WMV looks good it likely is good.

BTW, DV on a firewire transport is what your ADVC-300 is putting out. It sounds like you didn't capture using Vegas, which would have prompted DV or HDV.

Many of the standalone capture applications convert to MPEG2 on capture. Some also change the pixel dimensions. Best to avoid all this.

This is all assuming that your PC is reasonably current.
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Old August 26th, 2015, 08:50 PM   #7
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Re: Mysterious lagging experiement

Okay...WMV seems to work good enough. But I do want to know how to do this right for the theoretical *next time*.

So...DV25 is avi, correct? I re-rendered the 6MB mpg to Sony DV and it came out as a huge 28MB/per second file (28 Gigabytes for a two hour film). Would it actually be worth capturing to this high of a bitrate from the tape - would quality increase 4-5 fold per the bitrate increase?

thanks guys

P.S. Jeff the XA10 you sold me is still going strong. Shot a 350 hour documentary on it and will be taking it full-on into post soon (spent a year indexing and conferencing on it to get clear on the underlying story). Although I am missing that 60p and salivating over xa20/GH3, etc.
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Old August 26th, 2015, 08:57 PM   #8
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Re: Mysterious lagging experiement

Quote:
Originally Posted by Jeff Harper View Post
I forget the reason that is so.
Lossy compression.
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Old August 26th, 2015, 09:15 PM   #9
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Re: Mysterious lagging experiement

Adjul, glad it's still going strongl! I recognized your name but couldn't place it. So glad it's served you well!
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Old August 27th, 2015, 10:44 AM   #10
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Re: Mysterious lagging experiement

Right - it's DV in an AVI wrapper. The AVI file type can have many different types of codecs.

In theory, that's the right way to do it upon capture. DV is what your ADVC-300 hardware is making out of your original analog tapes, and it edits very well, preserves all quality, etc. And you have an excellent method to capture DV with the 300 and Vegas; that's pretty much state of the art for quality that isn't ultra-expensive.

But this is a place where you shouldn't listen to internet experts very much, IMO. We're not looking at your footage. We're not seeing the quality differences, if any. If you're happy with the quality you get with other methods that's good enough. Only you can balance quality and cost on your projects. If this is part of your longer doc project the answer may be different; for example, if it may go to festivals or broadcast that can justify a little more obsession on video engineering issues with workflow shortcuts.

Do stay away from capturing directly to MPEG2 if you need to do any editing at all, and watch out for size changes. Your SD transfers should be 720x480 or 640x480. Some of those capture programs seem to make your clips suitable for instant emailing, at 360x240 or something. THAT is a HUGE quality hit. WMV at, say, 1.6Mbps/SD is very, very good! But I don't know how you capture directly to it.

Adam is right that MPEG2 has lossy compression, and that alone is reason to be suspect of it in early positions in a workflow, but the reason for the lagging is that the software decoder Vegas wants to use on it isn't keeping up. All these formats must be de-compressed for timeline playback. For a while there were cameras recording MPEG2, so there are some specialty editors out there that decode it just fine. There are unique codec variations in cameras and capture programs, maybe your install of Vegas would do just fine on one of the camcorder MPEG2 files.. And in a DVD player MPEG2 is being decoded in hardware... it's just not very universally decodable in software. I could go on...

OTOH, hard drives are cheap and forever falling in price, so the apx. 13GB/hr of DV isn't as expensive to keep around as it once was. That's over 100 hrs. of DV footage on a 1.5TB drive on sale at costco for $67. Less than a buck an hour. No wonder we don't use tape anymore...

Your XA10 is using later codec technology to fit HD into about the same size...
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Old August 28th, 2015, 10:08 AM   #11
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Re: Mysterious lagging experiement

Seth, Jeff, Adam, thanks a lot.

I see what I did: after Vegas rendered to dv/avi I saw that file size and freaked out. I also allowed some of the captures to overrun the tapes (a 4-5 hour capture for a 2 hour tape) which resulted in even huger files (60 gig files with half of them blank). So I decided to cut and re-render the files in vegas, and figured VHS didn't need such a high bitrate, so I downgraded them to mpg.

Funny, the 30gig originals (most of which I still have) work fine on the timeline compared to the 5 gig mpgs. Learning something new about compression and decoding.

This time, I'm going to use avidemux or some video cutting application to line up the new captures with the old ones (I built my project around old captures taken without the AVDC which resulted in a lot of shimmering and bad light performance) instead of re-rendering again, since the render work is already done in the capture.

Thanks again.
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