How to obtain best compression results

yirm wrote on 4/3/2003, 11:32 AM

I have a 90 minute video that I'd like to fit on one DVD. According to DVDA's optimize feature, it will end up being 113% of the DVD's capacity (won't fit.) If I want to make it fit, what parameters should I lower?

Another question. In the MPEG2 custom template dialog, on the first tab (project), how does Video Rendering Quality affect quality and/or filesize? Or is that just for material that needs to be rendered, not just converted (e.g., transitions, etc.), as the help implies?

On the video tab, the Video Quality slider --- does that just affect rendering time, or filesize as well?

And most importantly, the bitrate settings:

1) If I use the default constant bitrate setting (6,000,000), will that result in a smaller file than the default variable bitrate?

2) If I go with variable bitrate, do I need to lower just the maximum bps, or average as well?

To summarize, I need to fit 90 minutes on one DVD -- what are the optimal settings?

Thanks!

-Jeremy

Comments

BillyBoy wrote on 4/3/2003, 12:21 PM

First, did you change the disc size from the default 3.95 to 4.7 under Prefrences, buring? If not do that and that should get you closer and you won't be over the limit so much if at all.

If you need to fit a size X video on the DVD, you have no choice but to lower the bitrate unless you want to reduce the length of the video. Variable bitrate is better in that those parts of the video that need it get higher bitrates, while those that don't, don't get it. I would nudge down the max a bit and leave the average alone.

Optimal setting? The highest bitrate possible while still getting the whole video on the DVD. :-) That does NOT mean using a higher than the default bitrate either. If you do, that may introduce other problems, like some DVD players not being able to keep up with the data stream.

yirm wrote on 4/3/2003, 12:33 PM

Thanks for the response. Yes, I changed that preference. My 90 minute video is predicted by DVDA, at the default template to be over 5GB.

In Vegas, I tried rendering 5% of my video at a CBR of 6,000,000, and got a 218MB file. Multiply that by 20, and you get less tha 4.4 GB, which should leave enough room for menus and audio. I think that's what I'll do. If I did VBR, and moved the maximum down to 6,000,000, left the average at 4,800,000, I think the results would be worse, no? Also, I think VBR takes longer to render. I looked at my 5% of the video, and the live motion looked good. The titles (red on black) didn't look so hot. Maybe I'll render them separately.

I caught the Vegas Help's advice on not going above 8,000,000 for compatibility reasons.

Thanks for your advice.

Oh -- one thing I did notice is that my markers didn't show up in my 5% in DVDA. Do you have to render the whole file for your chapters to show up? My rendered AVI DV file did maintain the markers, and they showed up as chapters in DVDA. But unless they are appended to the end of the file, they don't seem to be included in MPEG2 files. Is that correct?

-Jeremy

Udi wrote on 4/3/2003, 12:45 PM

You should put 4.37GB as the max disk size. The 4.7GB is 4,700,000,000 while a real GB is 1024*1024*1024. In real GB is is about 4.37.
To be on the safe side, as dvda soes only estimation of the final size - don't plan to use more than about 90% - which will bring you back to the default.

yirm wrote on 4/3/2003, 1:04 PM

Oooh. Good advice.

-Jeremy