File size vs. Video Quality

burchis wrote on 10/28/2003, 10:53 AM

Vegas Gurus,

Is there anyway to determine the file size before rendering for various bit rates that are available?

I have two hours of A/V that I want to fit on to a single DVD. What bit rate must I chose to allow this to fit? I hope that I'm not overlooking something simple in the render tap.

Comments

vonhosen wrote on 10/28/2003, 11:21 AM

600/total number of minutes = AVERAGE bitrate for video & audio combined.

ie

600/120mins = AVERAGE bitrate avaiable for both video & audio of 5.0Mbs

If your audio is AC3 stereo at 192kbs you can encode your video at
4.8Mbs CBR
OR
VBR with say Min 2.0Mbs . AVG 4.8Mbs , Max 9.0Mbs.

That is assuming your total is 120Mins & doesn';t have motion menus. If you have motion menus you will have to include the total length of menu in minutes , add this to your 120mins & recalculate.

Jay Gladwell wrote on 10/28/2003, 11:28 AM

You might want to try this bitrate calculator, too:
http://www.dvdrhelp.com/calc.htm

burchis wrote on 10/29/2003, 2:18 PM

Thanks for these factors. Is this common knowledge or your personal experience from previous projects?

vonhosen wrote on 10/29/2003, 2:43 PM

This is just the math (& it has never failed me)

A 4.7Gb disc has 37,600 Megabits available.
When I first started authoring DVDs I read that I should allow 4% for overheads (navigation data, still menus etc)

Take 4% from that & you have 36,096 (Make it a nice easy round number without losing too much & you have 36,000)

So we have 36,000 Megabits to divide equally amongst all the seconds in our movies that are to be included in our project. That would give us the average bitrate for all our movies (video & audio)

Because we are working in seconds (& that's a lot of numbers) we can make it easier so instead of working on 36,000/number of seconds if we divide both sides of the equation by 60 we get

600/number of minutes = average bitrate.

(But remember still menus are included in the equation , motion menus must be counted as video for the purposes of the equation)

Softcorps wrote on 10/29/2003, 2:56 PM

DVD bitrate calculator

burchis wrote on 10/29/2003, 4:59 PM

Okay,

I'm glad that I posted this question. The replies that I have received has really educated me in this arena. Thanks very much for the bit-rate calculator. The break-down of the math help put everything in perspective too.

Does anyone, on the consumer level, record their DVD's on SS/DL or better format? How much do these DVD's cost, and I'm assuming the average DVD burner won't get the job done, so what would this cost?

vonhosen wrote on 10/30/2003, 12:35 AM

SS/DL ?

Are you talking Single Sided Dual Layer DVD-9 discs ?

If so you can't burn to these. Commercial discs are not the same as recordable media. Commercial discs have foil layers that have the data stamped on them & then sandwiched/pressed between two discs. These are made at a replicating house & minimum runs will depend on the replicating house but you are looking at say 1,000+

Recordable media use a dye not foil.

That said manufacturers of +R & -R drives have made press releases recently that they are developing/testing dual layer burners/media........so maybe in the future but not yet.