questions about making DVDs

slambubba wrote on 8/11/2003, 11:36 PM

i have a couple of projects done in vegas and i'm finalizing the DVD layouts. i've been doing some prototype burns using dvd+rw. i have a few questions.

1. do you use DVD-A or nero for your final burn? if you use nero, what format and settings do you use? i've tried DVD-Video and it complains about reallocation, but it seems to work on my dvd players. i think someone mentioned use UDF somewhere.

2. what's the lowest average bitrate you would recommend before the quality degrades noticebly? i think the default average bitrate of 6,000,000 will allow around 90 mintues of video.

3. if the bitrate is too high, is it better to adjust it during render using Vegas as apposed to having DVD-A rerender it? if video is like a JPEG, each save loses quality.

4. do you prefer +r or -r media for your final render? i'm looking for best compatibility with home players, not computer.

thanks for you help. vegas has been a lot of fun learning and this forum is a great community.

Comments

BillyBoy wrote on 8/11/2003, 11:50 PM

I see a lot of people ask about bitrates. I have NEVER changed the defaults. There really isn't a good reason to UNLESS you have special needs. Kind of one of those questions if you have to ask, it isn't for you. The defaults work fine 99% of the time. The two exceptions would be dropping the bitrate a little IF you need to squeeze a few minutues more on the DVD that you simply can't bring yourself to edit out. Go higher ONLY if you have very high action and you already burned at the default and think the results could have been better. Then using a constant birtate is probably a mistake. You'll need to fiddle with the average and high values of the variable rate to see what does best. Be aware many DVD set top players stumble at the upper end of the bitrate range.

As far as degrading so you'd notice it again depends on the quality of the video. Garbage in, garbage out. If you start will less than great source material then we're talking something else. For example if you downloaded something off the Web chances are it already had the #$# compressed out of it before it was uploaded, then rendering at a high bitrate is rather pointless because its getting compressed all over again. Kind of silly to even put on a DVD except for the size of the video, otherwise dump on a CD.

farss wrote on 8/12/2003, 12:04 AM

This is only what I do:
1. DVDA, if you've got it why not use it?
2. To fit the maximum amount of video encode audio to AC3. The rest of your question is very subjective and depends on many variables.
3. If you want to let DVDA adjust the bitrate so your video will fit bring in AVI files then there will be only one encoding pass involved. There's no harm in doing it the other way though, it does give you a little more flexibility and DVDA seems to calculate based on PCM audio whereas you can fit more video using AC3.
4. I started out as a DVD+R fan but am now leaning towards DVD-R as it does seem more compatible. Be aware however that the type of media is only one factor effecting compatibility. This area is a can of worms with no guaranteed way to get 100% compatibility.

starixiom wrote on 8/12/2003, 12:25 AM

Yeah, i noticed a lot of questions about changing the bitrate when authoring a dvd. I always just leave it at default and have never had a problem. I think that a lot of people assume that if you adjust this variable somehow its going to be the difference between Hollywood and Home Video quality. Its not.

Anecdotal: I wanted to finally own Gattaca on Dvd. They have two versions. A "normal" DVD with all the extras and a Superbit version with only the movie because of the higher bit rate. I bought the normal version for like $10 less and had a friend come over and we compared the two. To me there was absolutely no difference. The story was the same, the shots were the same, and the overall feel felt the same. He was trying to point out to me various scenes that appeared different, but I think it was more psychological than an actual difference.

So keep your settings at default and worry more about your source material.

slambubba wrote on 8/12/2003, 9:01 AM

thanks for the replies. i wasn't going to raise the bitrate thinking it would look better. i have a vacation video that is almost 100 minutes, and the default average bitrate of 6,000,000 is a bit too much to fit on a single dvd, even using the ac-3 encoder. so, i lowered it to 5,500,000 and didn't see a visible difference, and now it fits. i was mainly wondering with good source clips, at what average bitrate does the quality look noticebly worse. sounds like it might just be trial and error.

riredale wrote on 8/12/2003, 9:56 AM

Here's the formula: 600 / number of minutes = total bitrate.

For your example, 600 / 100 = 6Mb/sec. Since you are using AC-3 for audio compression, the audio portion of the total bitrate is about 0.2Mb/sec, leaving 5.8Mb/sec for the maximum average bitrate that can be used.

If your source video is very clean, it will compress nicely even at 4 to 5Mb/sec. If the source is noisy, the MPEG2 encoder will go nuts, and even a bitrate of 8Mb/sec will probably show artifacts.

Jsnkc wrote on 8/12/2003, 9:59 AM

One other thing to remember about bitrates that we run into a LOT. IF your DVD is going to be played back on primarily laptops you should try and keep your bitrates around 5MBs or less if possible. We have found that laptop drives have real problems playing back dvd's with high bitrates, usually 6MBs or above. We get people all the time that call and say, the DVD plays fine on their set top player, but when I try to play it in my laptop the video and audio is really jerky.

JumboTech wrote on 8/12/2003, 11:07 AM

If you have relatively little movement, you can get away with a low bitrate. If there are a lot of dissolves and complex visuals like when you shoot moving water, then you'll probably need a higher bitrate. I used to make SVCDs at about 2.5 Mbits/sec so anything above that can be considered a bonus. Of course, DVDs are 720x480 as opposed to 480x480 for SVCDs so they need a bit more anyway (no pun intended). It can be helpful to take the same footage and encode it at different rates to see if you can tell the difference. Just alter the average.

Regards...

Al