Comments

vonhosen wrote on 7/8/2002, 7:27 PM
If your file is 60mins long you could get away with using 8Mbs for video only (& add PCM audio at 1600Kbs) it will all fit on your DVD-R.

Your file size for 6Mbs & 60 mins will be 2.16Gb (or 2.01Gb for binary system)

In simple terms if you want to know what bitrate you can use just think of 600 & it will give you a rough idea.

Divide 600 by the minutes in your video & you will get what bitrate you can use for video & audio combined upto a maximum of 9.8Mbs.

i.e 600/74 = 8.1Mbs

If you are using PCM audio you will have to take out 1600Kbs from that 8.1Mbs to show you what is available for video
If you are using AC-3 or MPEG audio you would have to take out say 224Kbs from it.
MH_Stevens wrote on 5/23/2006, 11:45 AM
But if size is no problem which is best and why? With VBR what factors influence the rate VBR chooses?
johnmeyer wrote on 5/23/2006, 12:31 PM
You can use this bitrate calculator:

Bitrate Calculator

to get exact estimates (oxymoron: "exact estimate") of how large the project will be for any given bitrate. More important, you can tell the calculator how long your project is, and it will tell you what bitrate (either CBR or the AVERAGE for the VBR setting, it doesn't matter) to use. Try to stay above 6,500,000 for good encoding. This will give you at least 80 minutes on a single sided/layer DVD.
DGates wrote on 5/23/2006, 1:41 PM
I only use CBR nowadays. When I used VBR, there were areas that would get pixelated, especially in fades to black. When possible, I'll set the CBR rate to about 8 to 8.5.
Laurence wrote on 5/23/2006, 2:11 PM
I also only use CBR. VBR sucks during transitions and dark spots. I'd rather have a consistant quality all the way through than the patchy look VBR gives me.
MH_Stevens wrote on 5/23/2006, 3:00 PM
Why does Vegas specify VBR in its HD default templates and most others?
riredale wrote on 5/23/2006, 3:43 PM
Gosh, I don't know; I don't use the MainConcept encoder that comes with Vegas. I use CBR for short stuff, though VBR would even then be useful (keep average high, but set the max at 9Kb/sec). I can't imagine that a company as large as MainConcept would make an encoder that blew up on VBR, but I just have no experience with it.

The whole point of VBR, of course, is to carefully allocate bits to where they are needed, since some scenes need a huge bit budget and others practically nothing. In all the projects I've done with CinemaCraft I've never seen any of the "pixelation" that others are mentioning in this thread.
farss wrote on 5/23/2006, 4:20 PM
Needless to say to get the most out of VBR you need two pass encoding. Even more passes is better although just how much better I haven't a clue.

Bob.
johnmeyer wrote on 5/23/2006, 9:57 PM
I agree with Bob. VBR without 2-pass is not really VBR. Not much point to it. The only way the encoder can budget the bits is if it has complete knowledge about the motion in every frame in the entire project.

Of course to do a REALLY good job, there needs to be a way to manually override the encoder decisions, but this is only found on seriously expensive encoders, and requires time, patience, money, and skill -- something in short supply in these parts.

riredale wrote on 5/23/2006, 10:40 PM
An encoder can do VBR with just one pass, but it needs to guess as to how complex the frames are. The encoder programmers can guess based on typical video footage, but this means that your finished video might be +/- 20% of what you really wanted in terms of size.

By contrast, a 2-pass method means the encoder can look at every frame, and then allocate bits precisely so that the final product is exactly the size you specified.

I was lucky to find a copy of CinemaCraft on eBay. With it, you can do up to 10 passes (though more than 3 is not very useful) and you can also go in and override bitrates for portions as small as a GOP. Say for example that you did a render at a very low bitrate, and everything looks remarkably good EXCEPT for a single fadein, which is all pixelated. You can go into the GOPs making up that fadein and goose the bitrate up as high as needed in order to eliminate the pixelation. The net effect on the entire project is very small, because you're only increasing the bitrate for a very small portion of the whole project.