How to reduce render times?

videonewbie wrote on 11/24/2002, 1:14 PM
I have a 90 minute video that I am intending to put on DVD. I am rendering it with VF to MPEG2. On a 1.4GHz machine with 1 GB RAM it is taking 4.5 hours to render - about 3:1 ratio. I'd like to reduce this.

The Video was captured to MPG2 by a Dazzle DVC-100. This was imported into VF, edited and then rendered to MPG2. It occurs to me that because the input and ooutput codecs are different, there is a lot of unnecessary decoding/encoding going on during final transformation. (This is purely a speculation since, as my username indicates, I am very much a neophyte in this world.)

Since I am likely to do multiple "final" renders, it occurs to me that the following method might be quicker overall, so I present if for comments. Comments like "You are nuts, it doesn't work that way" are welcomed.

I could import the originally captured MPG file into VF and then render it totally unchanged to a new file, encoded by VF and the SonicFoundry codec.
Then I could edit that file in VF and the final render should be quicker since this original and destination encodings are identical. (This makes the assumption that VF is smart enough to copy portions of the input video that have not been altered to the output without decoding and encoding. Is this correct, or am I full of horse exhaust? If the latter, how can I decrease render times without significant degradation of output quality.

As an aside, I appear to be capable of storing only about 90 minutes of video on a DVD - yet store bought ones contain much longer videos. What accounts for the difference?

Thanks in advance,

Martin H

Comments

Chienworks wrote on 11/24/2002, 1:53 PM
Actually if either the source or destination are anything other than DV .avi or uncompressed .avi you'll be uncompressing and recompressing. The best and fastest method is to capture as DV .avi and edit in that format. Save MPEG until your final render. You'll get a better quality picture this way too.
videonewbie wrote on 11/24/2002, 4:35 PM
Thanks for the tip. The problem is that the DVC-100 will only capture in MPG2 format and while I am thinking of taking it back and getting the Canopus ADVC100 converter I have some tapes already captured that I no longer have access to so I am stuck with those in MPG2 format.

I guess I am stuck with long render times, but 3:1 does seem excessive to me, for a 1,4 GHz processor.

Martin H
Chienworks wrote on 11/24/2002, 4:37 PM
For what it's worth, those render times for what you're doing are about normal. Doesn't that make you feel better now? No? I thought not. ;)
IanG wrote on 11/25/2002, 3:19 AM
Regarding the amount of data you can get on a DVD, the "store bought" ones are multi-layer. Domestic kit can currently only manage a single layer.

Ian G.
Stiffler wrote on 11/25/2002, 10:47 PM
I wish I could have returned my DVC-80, but I just gave it away after getting a Digital-8 camcorder.

If you still have the option of returning the DVC-100 and get the Canopus, go for it.
ralphied wrote on 11/26/2002, 9:40 AM
Working with MPEG-2 files in VF (or any other video editing software for that matter) is very iffy. My experience has been that you can expect dropped audio and audio out of sync with the video when working with MPEG-2 files generated from hardware encoders like the Dazzle equipment or the ATI All-in-Wonder video cards. Like Chienworks said, you should work with DV .AVI files if at all possible.

As for render times, I use TMPEGEnc to render my DV .avi files to MPEG-2 and the rendering time ratio is almost exactly 3:1. You have to realize there is A LOT of numerical processing going on when generating a MPEG-2 file. Also, most of the low-end software encoders do not take full advantage of the multi-processing capabilities of the Pentium-4 processor.

The issue of the amount of video you can get on a DVD is a pet peave of a lot of people new to the home video market. Like you said, the commercial DVD's give you 2 hours worth at very high quality. What's even worse is that the marketers of the home video equipment (hardware and software) often claim you can get 2 hours of video on a DVD. The reality is, given the low-end hardware and software used in the home market, 90 minutes of decent quality video is the best your going to get, it's that simple. You probably could get 2 hours of video on a DVD if you use a MPEG encoder that gives you a lot of control over the rendering settings (such as TMPEGEnc), and you don't mind settling for lower video quality.
Simmer wrote on 11/26/2002, 4:41 PM
Yeah, this one bit me.

The maximum I've found I can get on a 4.7Gig DVD (single layer home product) with high quality, is about 1 hour (depending upon menus, animated menus, associdated audio for the menus, etc.).

So, I end up having to create a 2-DVD set for each 2-hour video I make.
Fortunately, you can buy 2-DVD cases.
That, at least, seems to help me keep the 2-DVD set together.

-Mike
IanG wrote on 11/27/2002, 3:47 AM
I've just stumbled across this very useful tip from Chienworks.

Ian G.