Compression for menus

Rich Reilly wrote on 10/17/2007, 9:36 AM

If video clips are pre-encoded, is there any drawback to upping the default video birate to preserve graphics quality?
It would only apply to stills (menus)so I would think you could go as high as 9.5 or so?
Thoughts?

Comments

ScottW wrote on 10/18/2007, 6:50 AM

True still menus are encoded as a single I-frame and it doesn't get much better than that for quality since the entire screen is present.

Motion menus though.... Since DVDA is going to re-encode a motion menu 99.5% of the time, and it's been a while since I last looked, but I don't recall any way to tell DVDA what bitrate to encode the motion menu at, then you are better off starting with source that hasn't been compressed or has received as little compression as possible. If you must start with compressed source material, then yes, higher bit rates will usually be better, but don't expect DVDA to maintain that bit rate into the end product.

In general, I don't like to push the limits of something, because that's usually where you run into problems. Sure, the spec may say "bitrates up to ..." but at the top end, more equipment has trouble handling it.

The other option is to use an authoring tool that doesn't re-encode the motion menu. I will frequently encode motion menus for DLP at 8Mbps.

--Scott

MPM wrote on 10/18/2007, 8:31 AM

"...it's been a while since I last looked..."

FWIW & in case it helps, the project default is applied whenever DVDA has to (re) encode.

DVDA will skip re-encoding mpg2 menu backgrounds if you delete the menu title, and only use empty buttons --> image type with no image file, used as frames in DVDLab if I remember correctly. Since the menu title is how you keep your project organized, I'd say the estimate of DVDA re-encoding 99.5% of motion menus perhaps a little conservative. ;?P

Personally, I tend to save a *completed* project under a new name, then go thru & delete all the menu titles that according to the optimize box trigger a re-encode. Then render the DVD. Not terribly efficient if it turns out I have to edit &/or do corrections, but with menus &/or video I prefer to know what I've got going in.