Editing from DVDs and compression loss.

xarru wrote on 1/8/2008, 3:58 PM
I just quickly wondered if I put the contents of a DVD on my timeline, edit it, then save it as an MPEG2 if I lose quality in having what is essentially an MPEG2 file recompressed as an MPEG2 again?

What I'm up to is that several years ago I burned 30+ hours of family videos to DVDs.
I'd like to go through and edit them down to perhaps a couple hours of my favorite moments.

I can place the DVD footage on my Vegas timeline, but if I then save it as an MPEG2 will it be lossy?

I notice that if I save it as an AVI I get a huge increase in file size, so I assume it gets "rezed up" when saved as an AVI which is weird.

Does anyone know the ins and out of this, and what my best option for preserving these treasured video's quality is?

THANKS!

Walt

Comments

JohnnyRoy wrote on 1/8/2008, 5:09 PM
Yes it will be lossy but it might not be as bad as you think if the original quality was good. You might want to re-render one file to a DVD just to see if the loss is acceptable to you. Otherwise you'll have to use a editor that will not re-encode. I have a copy of Womble MPEG Video Wizard for just these times. It will allow you to cut up an MPEG file and it will copy the pieces that are left out to one file without re-encoding. This is your best bet if you are just making cuts.

~jr
Laurence wrote on 1/8/2008, 9:09 PM
Mpeg2 video is only smart-rendered in Vegas if it is HDV resolution.
johnmeyer wrote on 1/8/2008, 9:32 PM
If you get Womble, you can get exactly what you want, namely the speed and fun of editing in Vegas, combined with lossless MPEG-2 cutting. It is quite simple.

1. Download Womble: Womble

2. Download the Vegas EDL to Womble converter: EDL to Womble.

3. Put the MPEG-2 files (or VOB files, if they can be read directly) onto the Vegas timeline. Do a cuts-only editing session with just the video and audio track.

4. After you save the VEG file, go to "Save As" and change "Save As Type" to "EDL Text File."

5. Fire up the EDL to Womble converter, and specify the file you just saved in Vegas as the EDL file. Specify an output file, and then click on "Save." The Womble utility will ask you if you want to open the result in Womble, and you say yes.

Voila! All your edits show up in Womble. You then simply use the Export function, and you should be able to get all the video exported, with no recompression except for a few frames at edit points (you need to change the edit options in Womble so that you can cut anywhere, not just on "I" frames).

It's a damn shame that SF/Sony has had to rely on MainConcept all these years. Five years ago I predicted, in this forum, that many, many people would want to edit the DVDs they created, but would not have access to their source footage. This is, of course, exactly what you want to do. All the medium and mid-range editing programs let you edit your DVDs without recompressing. Sadly, Vegas does not. However, with this workaround, you can get pretty close to what Vegas should do on its own, although you will have to pry a few dollars or Euros loose to purchase Womble.

nolonemo wrote on 1/9/2008, 10:53 AM
John, can you use the cheapest basic version of Womble to do this? Thanks.
johnmeyer wrote on 1/9/2008, 12:27 PM
John, can you use the cheapest basic version of Womble to do this?

I think so, but I don't have that version, so I am not sure. The WBP file created by the utility is pretty basic, so I think it would load. Since the utility takes less than five seconds to download and is free, you should just try it out.

I've done five projects in the past three days using this workflow. I need to transfer several dozen VHS tapes and don't have time for my usual noise reduction, etc. So, I simply capture using my old ATI 8500DV capture card, using MainConcept's capture (it's in their standalone MPEG-2 encoder). This captures directly to MPEG-2, even at low bitrate is plenty good enough to get excellent results, even from S-VHS SP source material. I'd be hard pressed to tell the difference from 2-pass "tricked out" encoding using the external MainConcept encoder. I then put the resulting MPEG-2 on the Vegas timeline, do a cuts-only edit, add chapter marks, and then follow the workflow outlined in my last post. Womble only takes a few minutes to create the final MPEG-2 (I always use a separate disc from the source, which improves performance considerably). I then used the markers to DVDA chapter script to export the markers so that DVDA can read them. I do a very generic DVDA disc, spending less than five minutes, and I'm done.

UlfLaursen wrote on 1/9/2008, 12:50 PM
I have done some editing from DVD camera to DVD. It is ok in my oppinion, but I think there will be a loss. I think it might also have something to do with the bitrate too from the source.

/Ulf
baysidebas wrote on 1/9/2008, 12:53 PM
At half the Womble cost [last time I looked] VideoReDo Plus and VideoReDoTVSuite [a few bucks more but includes DVD authoring capability] will do mpeg frame accurate editing with no re-encoding [except the few frames in a GOP if cuts aren't made on i-frames]. Fully functional 30 day trial available.

http://videoredo.net
johnmeyer wrote on 1/9/2008, 2:24 PM
I have done some editing from DVD camera to DVD. It is ok in my oppinion, but I think there will be a loss. I think it might also have something to do with the bitrate too from the source.

There will be ZERO loss using my workflow (except for a few frames at edit points).

At half the Womble cost [last time I looked] VideoReDo Plus and VideoReDoTVSuite [a few bucks more but includes DVD authoring capability] will do mpeg frame accurate editing with no re-encoding [except the few frames in a GOP if cuts aren't made on i-frames]. Fully functional 30 day trial available.

That is true, but unless they offer an EDL converter, you will have to do all your editing in VideoReDo. The beauty of the Womble approach is that you can edit in Vegas and then let Womble create the MPEG-2, with zero re-compression. Also, the actual "render" (not really at render except at edit points) takes a few minutes instead of hours.
xarru wrote on 1/9/2008, 6:35 PM
THANK YOU ALL for the SPECTACULAR replies. I've downloaded womble and will print your recommended work flow to follow.

I have another novice question, but if I were to place the files from the DVD on the timeline, and save them as DV AVI files, would this also preserve them at the same quality?

I'm so USED to having to conserve hard drive space that it didn't occur to me that my 500 gig external actually COULD handle that. (Wonders of technology!)

I could then edit in Vegas normally add titles, transitions, music etc. Though, in rendering back to MPEG2 for the final DVD, I guess I'd get one step of loss there...

Is this correct thinking?
owlsroost wrote on 1/10/2008, 1:00 AM
Vegas Pro 8.0a **can** 'smart-render' ordinary SD MPEG-2. It's not an advertised feature but it does work - I've done several simple projects recently using the feature.

The tricky part is that you need to create a custom MPEG-2 render template which matches the parameters of the source files i.e. bitrate (the value in the MPEG headers), CBR or VBR, frame size, frame rate, field order and GOP length. Vegas can't give you all of this information so you need another utility to find this e.g. Bitrate Viewer [url=http://www.tecoltd.com/bitratev.htm]. The GOP length is probably best sorted out by trial and error - it's almost certainly 12 or 15.

When it's all set up correctly, you should see a 'No recompression required' (or similar) message in the preview window during rendering (other than at the edit points).

It's not as fast as Womble either for scrolling during editing or output file production (I've used Womble and MPEG-VCR for years) but so far the smart-rendered output seems to be OK.

Tony