Easy Question for You pros CBR/VBR ??

Hi all,
Ok, I need a little help here. It's late so bear with me...

If I calculate the bitrate to be 6000 for a particular AVI I want to encode to mpeg2 but want to use VBR, not CBR; what do I put for the Max/Avg/Min? 6000 across the board? That doesn't sound logical, but I don't want to "waste" space. By that I mean, if I set the bitrate to 8000 Max/ 6000 Avg / 4000 Min, will that "fill" the DVD or come in at like 2GB? Conversly, I don't want a 5GB file either. I know using CBR the calculator is going to give me the correct bit rate to get me close to 4.37GB everytime. Basically, if you were in the situation described above, what would your settings be and why?

I searched for this topic (honest I did) and didn't come up with any answers. Forgive me if I looked in the wrong place...

Thanks in advance....

Originally Posted by lordsmurf

Use the bitrate calculator on this site.

I do use the calc on this site. Pls show me where it tells you what to put in for the Max/min values...

I question the logic or rationale of it for VBR. I guess if you set the Avg to what you calculate the bitrate to be, the max and min will have no effect on the file size? Obviously setting the Max to more than 6000 and the min to less than 6000, from the 1st example...is that correct?

@ Lordsmurf
I know you know your video stuff like the back of your hand and I obviously would never question your expertise, but when I posted this I was hoping not to get a smug response from you. I'm not sure if you realise it or not, or even care, but people who look to this site for help will do so less frequently if they know they will be made to feel less than smart when they post. I mean really, how much help do you think your answer would give me considering what I asked?

Thank you both for the knowledge transfer I was looking for. BTW I use AC-3, not PCM.

As far as me needing to take a grain of salt, I stand by what I said in my first response. Even if I was a complete noob, the first answer I got wouldn't help anyone. I was just letting LS know that sometimes his posts come across as condescending. Whether he meant it as such, I don't know.

Again, I thank you guys for the help.

Different encoders will respond differently.

Numerous tests showed me that CCE, for instance, will consistantly undershoot the AVG value unless a fairly high MAX value was applied. It seemed to smooth out the spikes in bitrate.

TMPGenc seemed to need a somewhat lower MAX value, it would get more extreme in the spikes and consistently overshoot the desired AVG.

MMC seems to work best when the MIN-MAX-AVG range was very narrow, 500-1000 for each gap. MMC tended to have severe bitrate "valleys" resulting in pixelation.

Originally Posted by lordsmurf

For Half D1, 1000 is almost getting to be too high.

For Half-D1, why VBR anyway? CQ does the job excellently. Crisp & clear!

Thanks guys, I appreciate the insight!

Originally Posted by NamPla

Originally Posted by lordsmurf

For Half D1, 1000 is almost getting to be too high.

For Half-D1, why VBR anyway? CQ does the job excellently. Crisp & clear!

CQ IS VBR. Its just one pass VBR with no way of guaranteeing the final file size.

Don't get me wrong, Tmpgenc's CQ mode produces excellent quality results (IMHO) but has a big drawback of not being able to know the final filesize in advance. So when trying to squeeze max play time onto a disk, irrespective of your resolution, it can be hit and miss.

I would set it to D1 8000kbps CBR to encode,author to DVD files then use DVDShrink to transcode.
I use this method all the time with excellent results.

@daamon

Great insight, I GET IT NOW!!!
Yahoo!
Thanks again guys...

LOL....I just did my 1st VBR conversion! Here is a comparison...please tell me it's "worth it"...

A 2.5 hr AVI, if done with CBR = 3 hrs
VBR 2 pass = 12.5 hrs!!

Holy frijoles!!!

Well...I am using Vegas 5....have been for over a year. I have converted about 20 Steeler games to DVD, each one about 2-2.5 hrs in time and CBR takes about 2.5-3 hrs.

I use the DVD architect template (no audio) and plugged in the VBR values...I did change the size to half D1. Maybe thats why it's taking so long. But I started it last night and it ran overnight, took a little over 12 hrs.

Ahhh, I see. I figured it was that. Thanks again to everyone for the comments and help.

What Capmaster said above is so true, and I agree with him on them

These days, I prefer CBR at 9000 bitrates. I'm refining my process
still. But, CQ offers a lot as well, to those that don't want CBR
in their process.

Some encodes work better w/ different MODE settings than others.
For instance, CBR does better on Interlace-only sources (such as CAM
footage) vs. VBR. Because (IMHO) VBR does not help enough
when the scene is very fast. And, I've come to beleive that as long
as you think in tirms of 60 minutes to a DVD (home footage) that's
the goal. And, CBR at 9000 seems to closely make it. (I'm having
trouble hitting that mark - fitting 60 min on a DVD disk w/ CBR, but
I suspect I'll figure it out) .. plus, w/ CBR (and home footage) you
will not have to wait those long hours.
.
One more point about footage (even though it was not mentioned above)
If we all used a tripod in our video footaging, we'd have less worrys
w/ Bitrate settings ..The only reason why CAM footage is soo
probablem matic, is because many still take footage by hand.. instead
of a tripod. ..END OT.

* jimmalenko wrote:

As bugster said, if hitting a target size is important (and it is to me ) then CQ is not really appropriate.

Not so. (read below for in-depth) ...

In short.. a one hour program (be it TV or CAM footage) and CQ, WILL
fit on a DVD disk Really !!!
What is needed at the moment, if a fine-tuned CQ recepie
Because CQ is not CBR, there is a *greater* chance of fitting a 1 hour
tv program/CAM footage on a single DVD disk. Yes. Anyways.

And, absolutely NO FILTERING is needed ! ! ! !

Here's another great reason/advantage to using CQ (TMPG)
in your DVD projects.. (assuming that is your final goal) ...

* Speed
* Quality

Ok. Lets say, you have a 90 ~ 120 min movie, but you don't want to wait
the hours of multi-pass encode (tipically 2 pass) and need the speed (as
we all do) and *quality* thereof..
.
You could do it w/ 2-pass (w/ semi gaurantee of quality) *or* you could
go the CQ route, and go for broke.. because your final destination is DVD
..but half the time. CQ offers that.
.
You don't have to worry about space, fitting on a DVD disk, because the
chances of a 2 hour movie (using CQ) not fitting on a single dvd disk is
almost nil. And, if your movie is 60 minutes, you have a MUCH greater
chance that you'll come out winning no matter what. Even if you have plenty
of dvd disk space left over. (next time, calculate your bitrate / CQ values
better w/ a little extra nudge) Before you know it, you'll do winging it
w/ a blind-fold over your eyes

If you use VBR (2-pass) you're gonna be waiting. Plain and simple. Quality ?
Well, I believe that there is just too much hype w/ multi-pass encodes.
CQ offers very good quality. It suffers one draw back. And that is, knowing
that final outcome. That is, if your source is greater than 90 or minutes,
and you want specific numbers in your final projects.

With CQ, you can gain speed and have quality at the same time, and w/ a little
practice, be able to juggle the CQ values needed for a good DVD encode project.

Ok. Scerio.. something to think about ...

Lets say, you want to capture and encode a 60 minute movie. You might get away
with it using CBR and 9000 as your bitrate (though I have doubts that it will
succeed and fit on a single DVD) .. However, lets continue..
.
So you capture this 60 minute program, and you choose a CQ mode as your encode.
I like quality, so I"ll set my params as:

* min: 4000 ~ 6000
* max: 9000
* CQ: 74

*note, I've never had a problem with this, but there is always a first. But
as I said (as a hint/nudge above) you learn these things as you go, and get
better at it, till you can do w/ blind-folds on.
.
The above is not etched in stone. It's something I was working (though I stopped,
due to other events and things)
.
Lets continue..
.
Now the encode is complete. You find that your 60 minute tv programs' encode
had left you with plenty of space left over. Well, thats something for you
to work with later, in your next CQ Encode project .. but,
The first thing you *could* do, is verify the level of quality.

* Was it good ?
* Was it poor ?
* Did you conclude you could have raised the CQ value a bit, (or bitrates) ??

These are things you can play with, and gain the necessary knowlege (next time)
till you become better at it.
.
But, so what.. you had plenty more space left over on your DVD disk. Your
goal was fitting a 60 minute program on a DVD disk. You succeeded. You can
play a little w/ the settings and get better at filling the disk (if thats
at all important to you) but its not necessary, if A) the quality is there,
and B) you met your goal (that being, that you didn't go over-board of your
disk space)
.
There are all kinds of scenarios w/ CQ encodes. The above was *just one*
example. But, think about it for a moment. What do you really want ?
.
My point above, w/ respect to CQ, is that if you are growing tired of the long
waits for multi-pass encodes, and (after factoring "dvd" specifics) your goal
is DVD, then it might not be such a bad idea to learn this mode of encoding
that TMPG has to offer. Actually, it's CQ mode is very good. You just have
to *spend* the time to learn and feel for it. But, that's only if you are
willing to learn something new.. Otherwise, you're best to just stick with
multi-pass VBR and wait, and wait, and wait, and wait (well, you get the idea)

So, again I ask... think about it for a moment. What do you really want ?
CQ offers as much as VBR, but w/ one missing advantage. And, I just explained
above, why even that limitation is nil. Anyways.

Don't forget, I'm speaking for TMPGenc w/ regards to CQ and the above cents
worth.

The above was my many cents worth,
-vhelp

Originally Posted by vhelp

* jimmalenko wrote:
As bugster said, if hitting a target size is important (and it is to me ) then CQ is not really appropriate.

Not so. (read below for in-depth) ...

In short.. a one hour program (be it TV or CAM footage) and CQ, WILL
fit on a DVD disk Really !!!

Of course it fits. It is physically impossible to make a 1 hr compliant DVD that won't fit on a DVD5. Max out the video bitrate and max out the audio bitrate and there will still be room on the disk. This is not evidence that CQ is viable where target size prediction is necessary, it is simply evidence that the DVD standard was intended to be used for more then just 1 hr of content per disk.

If you've only got 1hr of content it really doesn't matter whether you use CQ, CBR, or VBR because the efficiency of bitrate allocation is pointless when filesize is of no concern. I don't see any reason to use anything other then CBR in this case.

But when encoding enough footage that bitrate allocation is a concern, multi pass VBR is the safe bet. You can be sure that you will hit your target size exactly, and you can generally be assured that the quality should reach the point of diminishing returns at that bitrate with that encoder. With 1-pass VBR, you can also reach this same point of diminishing returns, and in a much shorter period of time. However it requires some pre-encode quality tests and there is the risk that you will stray enough from either your target size or target quantization level that you will have to go back and do a second pass. Personally, I'd rather just set it to do 2 passes from the start and leave it alone. Yes it takes longer but it requires less micromanagement and ultimatley less of my time. If you've got a slower pc your priorities will be different but personally I find 1 pass encoding useless unless you've got an undecided amount of content to encode. Then you can just shoot for the maximum Q (higher Q=lower quality) you can live with and fit as much content as you can.