overall bitrate/high-low-typical/preview/edit window bitrate ?

[spydymn]

Hi when i backup my movies i try to keep my bitrate around 3500 & i normally use the overall bitrate number i get after prepare stage to judge that.i just started using the preview edit window & noticed that that gives a diffrent bitrate number as well.my question is what should i use to judge my bitrate
overall or high low typical or in preview edit window.I did 2 tests 1 test full backup movie/extras & no space stole from extras the other test the exact same but with 33% stole from extras,test 2 didnt show any diffrence in overall bitrate or high/low/typical or space for video even tho i stole 33% from extras,why didnt it show a diffrence on overall bitrate.the preview edit window is the only place it showed a diffrent number after the 33% stole from extras. here is a clip of my 2 tests any help or info on this would be great so i can understand it more & determine what number i should use to judge my bitrate. spydymn:)


- Reduction Level for DVD-5: 43.2%
- Overall Bitrate : 2,511/2,008Kbs
- Space for Video : 2,824,166KB
- HIGH/LOW/TYPICAL Bitrates: 8,424/600/2,008 Kbs
[08:43:09] Phase I, PREPARATION completed in 30 minutes.


-- Feature bitrate 2,335kbs in preview/edit window with 0% steal space from extra's.

-------------End test 1 -----------------------.


- Reduction Level for DVD-5: 43.2%
- Overall Bitrate : 2,511/2,008Kbs
- Space for Video : 2,824,166KB
- Movie improvement from extra reduction = 27.2%
- HIGH/LOW/TYPICAL Bitrates: 8,424/600/2,008 Kbs
[09:24:41] Phase I, PREPARATION completed in 29 minutes.


--Feature bitrate 2,971Kbs in preview window with 33% steal space for extra's.

------------End test 2-------------------.

[hallway]

The "overall" numbers are for the entire DVD (I believe). When you look at an individual piece of the DVD in the preview window, that bitrate is for just that piece.

Your feature bitrate numbers before and after stealing from extras makes sense too. Well, showing more available after stealing does, but the math doesn't add up exactly. 2335/2971 works out to closer to 22%, not 33%. I'm very sure there's much more to it than that though! I did just notice that DVD-RB reports a 27% potential improvement by stealing 33% from the extras. Between 22% and 33%, 27% is pretty close to the middle.... :)

Somewhat off-topic: What does HIGH/LOW/TYPICAL refer to ?? The original movie or the projected after-encoding numbers ??

[jdobbs]

Hmm... multiply 2335 times 1.272 (a 27.2% improvement) and see what you get (considering rounding)?

Remember that the extras and the feature are not the same size. So a 33% reduction in one could very easily represent a 27% increase in the other.

The overall bitrate doesn't change just because you've shifted from one part to another... it is determined by the output target size.

[spydymn]

thank you jdobbs, i see by multiplying those numbers as you said works out & i understand that the overall wont change unless i cut out all extras & just do main movie & menu only. so does - Overall Bitrate : 2,511/2,008Kbs mean
main movie 2,511 kbs & extras 2,008 kbs or am i completely wrong there,i know these are all prefrencies what might suit me might not suit someone else.
so to reach my goal to keep movie at 3500 i would use the preview/edit bitrate number as this is for main movie only or am i wrong there as well :).& forget about overall bitrate # if i dont mind the xtras being lower qaulity

[jdobbs]

No. That means the 29.976 rate is 2511Kbs... and the 23.976 encoded rate is 2008Kbs... it depends upon whether telecining is in use or not. It's related to the way DVD-RB handles encoding using a common denominator framerate on NTSC sources. (it does it so it can properly handle streams that are hybrids). The first number the the important one.

[spydymn]

Thank you again jdobbs for your quick reply,I am starting to understad it more now & have some more reading to do :) so do you recomened using the preview/edit bitrate # to determine the bitrate for main feature then

[spydymn]

Anyone ! Am i correct to use the preview/edit bitrate # to determine my bitrate for movie so i can keep my backups around 3,000 kbs or higher

[jdobbs]

Yes. That will give you the correct average bitrate for the VTS containing the main feature.

[spydymn]

Thank you jdobbs for your quick reply & all your help :)

[potatoe]

I got a question about the preview bitrate.

Assuming menus and extras are stripped, most of the time the reported feature bitrate in the preview window is equal to the Typical bitrate or the 2nd Overall bitrate reported in the status log.

However, sometimes the preview bitrate is equal to 1.25 x Typical bitrate or the 1st Overall bitrate in the status log. Why is that?

[jdobbs]

Because on NTSC sources DVD-RB uses a common denominator bitrate to encode of 23.976fps. It does that to handle hybrid sources (that are a mixture of 23.976fps and 29.97fps). The encoded output is then corrected to the proper bitrate during REBUILD.

29.97 / 23.976 = 1.25.

Please note, also, that no frames are lost. Only the rate is changed.

[Incognitoid]

along this same line of questioning, i recently had to re-encode a feature manually with cce (long story). It was a FILM source I telecined to 29.97 fps with 3:2 pulldown. I ran the vobs through the prepare stage in rebuilder first to get an idea what bitrate to use for cce. I used the FILM bitrate first and got an 'undersized' output, then used the VIDEO bitrate on the next pass and the output was pretty much dead on for target size.

I suppose my question is why did i need to use the VIDEO bitrate?

[Fishman0919]

- Reduction Level for DVD-5: 43.2%
- Overall Bitrate : 2,511/2,008Kbs
- Space for Video : 2,824,166KB
- HIGH/LOW/TYPICAL Bitrates: 8,424/600/2,008 Kbs
[08:43:09] Phase I, PREPARATION completed in 30 minutes.


-- Feature bitrate 2,335kbs in preview/edit window with 0% steal space from extra's.

-------------End test 1 -----------------------.


- Reduction Level for DVD-5: 43.2%
- Overall Bitrate : 2,511/2,008Kbs
- Space for Video : 2,824,166KB
- Movie improvement from extra reduction = 27.2%
- HIGH/LOW/TYPICAL Bitrates: 8,424/600/2,008 Kbs
[09:24:41] Phase I, PREPARATION completed in 29 minutes.

wow, that's a real.... long time for the that