How to Know Exact Bitrate when Converting AVI > DVD ?

[Somebla]

Hey, i'm looking for a way/guide to convert multiple avis (Divx, Xvid) and also mpegs to a DVD format (m2v if i'm correct).
I know how to do so with TMPGENc Xpress but my probelm is when I get to the bitrate.
for example, I could take a simple avi\mpg that runs for 30min and is 300MB and give it a max bitrate of 9200 kbit/sec which would blow the size to aprox 2000MB which is just a waste of MBs.

So what I would like to know is how do I know how much kbit I should put in the bitrate for each file - not to low to not harm to quality and not to hige to not waste MBs.
Is there a program that could give me the exact bitrate to convert from avi\mpg to DVD ?

Thanks.

[suppafreak]

have you tried bitrate calculators. There are couple of them in the Tools sections. Just search for bitrate calculator.

[mats.hogberg]

Generally, a regular DivX/XviD AVI requires about 4 times the AVI bitrate when encoded to mpg to make it full justice.

/Mats

[jagabo]

Or forget the bitrate and use Constant Quality encoding. The encoder will only as much bitrate as is required to get the specified picture quality. And it only takes one pass.

[mats.hogberg]

...and you have no idea how big the end result is going to be.

/Mats

[Somebla]

I only found 1 bitrate calculator, the VideoHelp Calculator and it dosent really help, because like I said i'm looking for a way to know the exact bitrate for convreting to DVD without lossing quality and wasting space.
That calculator just maxes the bitrate to full the CD\DVD.

mats.hogberg, isnt there an equation or something ?

jagabo, is that option available in TMPGEnc Xpress ?
and what does 'one pass' mean ?

last thing, for mpgs\mpegs I dont need to convert to DVD ? and if I do is it ok to use the same bitrate there at now ?

Thanks all.

[mats.hogberg]

You can set any size in the calc (advanced mode IIRC)
You'll always lose quality when reencoding. The higher bitrate the less, but always some. What's a waste of space or not, is entirely up to your own two (?) eyes. Noone else can tell you what's acceptable or not.
1 pass or mutipass differs, in that in mutipass, the encoder first takes a look at the whole movie, to determin where a high bitrate must be used, and where good quality can be maintained at a lower quality. You tell the encoder what avarage bitrate to use, how high it may go, and how low it may go. It then churns away, deciding how to distribute this. At a fixed file size, this is more efficient than fixed 1 pass bitrate, where the same amount of bits is used all the time, regardless of it's needed or not.
mpg's don't have to be authored to DVD, no. But for computer playback only, you're mostly better off with AVI anyways...

/Mats

[jagabo]

Sombela,

There is no simple equation that will tell you how much bitrate is needed for any particular video. It will vary from video to video. Bright, high action, high detail video will require more bitrate than a dark, static, low detail video.

Using Constant Quality you know what the output quality will be but you don't know the final file size. Conversely, specifying bitrate, (constant or variable) you know how big the file will turn out but you don't know the quality.

When I work with 30 minute episodes (which are usually more like 22 minutes) I don't care how big the files are. I pick a quality level I can live with then encode a bunch of files. I then put as many as will fit on a DVD. That usually means there's a little space left over but with DVDs a cheap as they are now I don't care.

I don't know about TMPGEnc Express -- I use TMPGEnc Plus. I rarely use 2-pass VBR or single pass CBR.