How to figure out best bitrate for a given space based on...

[Jason A]

An AVI file (or any other for that matter)..

I have my wedding which was all done in DVCAM format...I now have it all edited and ready in Premiere, ready to frameserver out to Tmpeg for mpeg2 encoding for DVD...

Using 4.7gig General discs, I can have my mpg file no bigger then 4.3gigs...

but the movie is 68minutes long....

At 5000cbr, I can only get 60 minutes max....

but in the beggining, where there is almost NO camera movment for 12 minutes, 3900 looks fine, but in the dance hall, with 120+ people acting like fools doing the twister, 6300/sec is about what it takes........

I'm running a 2.3ghz P4a but when starting to encode in Tmpeg, 2 pass-vbr with a filter, I'm getting 32 hours to encode !!!!

I'd hate to encode that long and find my file is over the 4.3gb limit...

so...is there a program that will first look at the file, analyze it, then report back around what the final size will be ???

With CBR is easy, but I need VBR in this case..

Thanks guys,
Jason

[adam]

Follow the guides on this site they cover all this. All you need is a bitrate calculator. It will tell you what avg bitrate to use to fit x amount of time onto x amount of disks, in this case 1 dvd-r. Look in the tools section for a bitrate calculator.

[Jason A]

Hey Adam,

Thanks for the reply, but for some reason, I have a hard time believing that a 68 min file can be 8750 in cbr mode !!!!

According to Tmpeg, it's about 6000/sec....

So who's right ??? Who's not ???

Jason

[adam]

I'm not sure where you're getting your figures. If you use TMPGenc's wizard it has a specific setting for 65mins at cbr 8000kbits to fit on 1 dvd-r.

Both TMPGenc and the bitrate calculator (I assume you used the vcdhelp java one) are correct. It doesnt matter whether you're using CBR or VBR, the avg needs to be 8750kbits to fit 68 mins onto 1 DVD-R exactly. Of course you should lower this avg a little just to be safe.

[bugster]

adam, perfectly correct. WOuld just like to pint out that some DVD authoring proggys (Mydvd, Dvdit, Dazzle DVD complete to name but 3) will at least warn you or even reject mpeg files with a max bitrate above 8000 as they assume you need the remaining bitrate for audio.
Just something to be aware of!