bitrates

gmes29 wrote on 2/29/2008, 7:25 AM
i have a dvd-a project where the total space in gigs is less than the 4.7 capacity of a dvd. when i go into Optimize and click Fit to disc, it says i'm using 67% of the disc at a bitrate of 4.540. you can adjust the percentage by changing the bitrate and vice-versa so i was wondering - what would give me better quality: increasing the bitrate so i fill 100% of the disc (or close to it) while increasing the bitrate or keeping the percentage and bitrate at 67%, 4.540??
in other words, is it a higher or lower bitrate that gives you better quality?

Comments

Terry Esslinger wrote on 2/29/2008, 8:29 AM
Higher, within reason.
gmes29 wrote on 2/29/2008, 8:47 AM
thanx..
does make me wonder why Fit to Disc doesn't automatically stretch out the 67% to 100% as it does with renders larger than 4.7g.
Chienworks wrote on 2/29/2008, 2:39 PM
What source format are you giving to DVDA? If it's an MPEG file you already rendered in Vegas then having DVDA increase the birate can only be done by reencoding MPEG to MPEG. The quality cannot go up since it was already lost in the initial encode. In fact, the quality will go down because MPEG is lossy and every generation will be worse than the previous one. So, if you give it an MPEG at a certain bitrate that doesn't fill the disc, the best quality that DVDA can produce is to leave it at that bitrate.
gmes29 wrote on 2/29/2008, 3:40 PM
here's what i usually do..
edit original mpeg in VMS as part of project
render result to avi (assuming no loss occurs because it's uncompressed)
use avi as input to DVD-A

this could be wrong of course so i'm open to suggestions.
gmes29 wrote on 3/1/2008, 4:10 AM
looks like what i described above is wrong. i just rerendered my dvd-a project after doing the following:

edit original mpeg in VMS as part of project
render result to mpg
use new mpg as input to DVD-A

the dvd-a render was so much faster this way it was unbelievable. went from about 3 hrs to around 25 minutes. that's good but i'm still concerned that there's some loss occuring during the vms render. can anyone answer that?

also i noticed that the disc space used indicator was now yellow instead of red which is the first time i've seen that. any significance to the color?
Terry Esslinger wrote on 3/1/2008, 10:40 AM
Seems like by rendereing your original mpg to avi (which is probably DV.avi and is not uncompressed) and nthe taking it to DVDA which will rerender it to Mpg is causing additional loss of resolution. Rendering it as mpg in Vegas skips the additional rendering step and DVDA will accept it barring other problems (length etc) and not rerender. Should save time and resolution (and give you more control). I am assuming you HAVE TO start with an mpg source which is never a great idea as it is more a delivery medium.
gmes29 wrote on 3/1/2008, 10:50 AM
"I am assuming you HAVE TO start with an mpg source which is never a great idea as it is more a delivery medium."

pretty much. when i was still capturing from VHS, my capture device could only handle mpeg2. now i'm importing the disc images written to DVD via my DVD recorder which i've been told are in native mpeg format and therefore are written out as such when imported.