question about tv series and bitrates

[mrcleeo]

im currently backing out my csi miami seasons and ive come across a weird situation


season 1's discs are an average of 7.1 gigs and season 2 averages 7.3 gigs per disc

when i did season 2 the avg bitrate was 2990
when i did season 1 (note the smaller disc) the avg bitrate was 2300-2500 depending on the disc

it seemed odd to me to have a lower bitrate with a smaller disc so i put it in "the big 3" and the bitrate came out to 2992

i had blanked everything on the discs including the warnings and directors comments. Basically there was movie/menu. Did i do something wrong in dvdrb? This is the 1st time in many discs that ive backed up that ive come across this problem.

[Boulder]

What are the sizes of the menus? Does DVD Shrink show any differences between the two seasons?

[mrcleeo]

menu size is 23 megs (came like that on dvd) season 1
season 2 is 64 megs i think (came like that on dvd)

[jdobbs]

The bitrate involves two variables -- size and framecount. A lower bitrate probably just indicates the framecount is higher.

[mrcleeo]

why are the bitrates different in big 3 than dvdrb?


and are you saying the outcome will look the same?

[jdobbs]

I can only assure you that DVD-RB will give you the highest bitrate that will fit in the target size. I can't speak for what other packages may tell you.

You have to be careful with stated bitrates... for example, if it is an NTSC disc, many of DVD-RB's "encoding" bitrates are based upon a 23.976fps rate common denominator (which is required for support of hybrid sources). In those cases the actually bitrate for the resulting 29.97fps output would be 25% higher.

[mrcleeo]

im trying to understand :)

so you're saying if the csi dvd has 29fps the dvdrb bitrate is based on 23fps but in actuality the outcome is really 25% higher than the bitrate rb stated?

[jdobbs]

Yes -- assuming we are talking about NTSC.

For example, suppose you have a 3000 frame segment that being encoded at 23.976fps. If the calculated bitrate is 2300Kbs at 23.976, the same 3000 frames would have a bitrate of 2875Kbs when set back to 29.97fps because the framerate is 25% faster.

The method is a little complicated -- but it is the only way to reliably reproduce a hybrid input stream correctly. Methods that use "force frame" for example will almost always result in stuttering problems with a hybrid stream.

[mrcleeo]

yeah im doing NTSC

so im assuming, say the big 3 method says 2990 and dvdrb is saying 2500, it is gonna have the same visual output look.

thanks for your help man!

looking forward to more goodies to come in dvdrb

[jdobbs]

DVD Rebuilder sets the bitrate for each segment based upon the demand and information it collects when it scans the original stream. So every segment won't be encoded with the same bitrate... but the overall average bitrate should be approximately the same as Big 3 (assuming the same things are being encoded).

The bottom line is that given the same output size, the same number of frames, and the same frame rate -- all methods and all encoders have to end up with the same average bitrate. So if you use the same encoder and settings the output is going to be approximately the same as well.