CBR or VBR for MPEG2 master backups?

[waldi]

When I capture my DVs into PC, I only cut out the pieces I don't like, encode them into MPEG2 and save them on DVDs for editting later on.

I know that for the master backup, the best would be to keep the original tape or a DV file before encoding, but the files are too big and I'm recycling the tapes for my new recordings.

So my question is:

Should I always encode in CBR mode with the highest possible setting of 9800? (this is acceptable to me since the files are at least compressed with about 3:1 ratio, big files but managable)

or

Is it a waste of space and I should always encode in VBR mode?

Keep in mind that my home movies don't have to be more than 1 hour long so I don't have to worry about fitting it on 1 DVD.

I'm just not sure if CBR is a waste of space in this case, and if the quality will be noticeably better than let's say VBR min=3000, avg=6000, max=9800

[Jonas_Vedder]

Hey!
Well, i suggest you should read this page:

http://www.mediachance.com/dvdlab/tutorial/bitrate.html

It says there that in a certain point it's not necessary to increase the video bitrate because it wom't bring any more quality to the video..you need to analyse the graphic in that page and see what suites you more!

[monzie]

Hey!
Well, i suggest you should read this page:

http://www.mediachance.com/dvdlab/tutorial/bitrate.html

It says there that in a certain point it's not necessary to increase the video bitrate because it wom't bring any more quality to the video..you need to analyse the graphic in that page and see what suites you more!

At f*cking last!!
I've been going on for MONTHS that for 99% of all encodes you do no need MAX bitrates..ever...EVER...but no-one ever listens.........because your all stupid and obsessed with BIG NUMBERS.

Merry Christmas and a Happy New Year

[canadateck]

your all stupid and obsessed with BIG NUMBERS.

Merry Christmas and a Happy New Year

A bit Harsh..

[lordsmurf]

What's funny is that pretty much rips off the info I've had here for 6 months or more:
http://www.digitalfaq.com/capture/avivsmpeg.htm

They just added a bunch of techie-speak to make it longer and sound fancier, and then added some pretty colors.

But that's fine. Spread the knowledge. The more people that know this stuff, the better.

[vhelp]

I say "hogwash"

If your plan is what you say it is, in your first post, then you better be using
CBR at highest bitrates (for later re-encode etc)
.
In fact, I would raise it from its 9.8k value you have, to 12k or 15k instead.

Since storing AVI (DV avi's) are way too large, and MPEG-2 is your final
option, I would definately use the highest bitrate (for archival purposes)
Becuase, once you encode to VBR type mode, and your given scene(s) are
not enough to cover the cost, you'll pay for it later, when you no longer have
the masters (tapes, AVI etc) to try again with.

Your whole purpose is to use them as final masters, to edit/re-encode at a
more reasonable later date. Using VBR in this case is definately not the
appropriate one to use.

In fact, if your plan is to push your DV tapes onto DVD disks, in a more
MPEG-2 mannor, such as VOBs, changes are, most DVD Authroing apps
will not comply with those higher bitrate that I mention above - 12k to 15k
Instead, I would use ifoEdit for those higher bitrate, because it won't stall
your authoring and you can make your vobs. Then, later on you can rip them
to your hd w/ smartripper for instance, and work with them, when your process
skills, techniques have improved.
.
By useing CBRs at 12k or 15k (I would use 15k) you are in effect, making close
to AVI quality. Don't worry about low motion scenes being waisted on high
bitrates here. Cause if you did, you'd sort of be contridicting yourself if
the source was AVI (think abuot the high bitrate it is for every frame) but
you have maximum quality, in every frame.

That's the goal.

Good luck and cheers.

From the video workstation of,
-vhelp

[waldi]

The reason I thought about maxing at 9800 is that I've read that this way I could use smart rendering feature offered by Mainconcept, and I've heard that in order to use it you need to encode with the same settings.

This way my backups can be smaller, but at the end after re-encoding the file again (assuming smart rendering works), I will hopefully get the same results.

Let me know your thoughts on this. Have anyone tried smart rendering feature in MC or MC pro plugin for Premiere?

[monzie]

your all stupid and obsessed with BIG NUMBERS.

Merry Christmas and a Happy New Year

A bit Harsh..

It was Christmas Day...and I was rather tipsy...OK hands up, it a fair cop guv, I was 100% smashed on wine/port/sherry/beer/lager...and a few spirits. :P

[jimmalenko]

Well, the first thing I'll say is that AFAIK, the 9800 bitrate "limit" is only if you want the DVD playable on a settop DVD player, and as such, this is why a lot of authoring softwares complain about it. For archival purposes, you could go well in advance of this if standalone playback isn't required, since you're just storing it as a data file and not as a full-blown, authored, settop-playable DVD. From the two links I've just read though, it would seem that there's no need to go above about 9000kbps:


(I trust LS here )

Now IMO, the main issue comes when we talk about audio. I would assume that since you're going to edit, we're looking at PCM ?

I did a rough calc of 1 hour of video w/ PCM audio and got this:


As for VBR vs CBR, it's a no-brainer IMO. As you can see from the images above, 1 hour of footage can be encoded at 8200kbps with PCM audio and *still* fit on 1 DVD. As vhelp said, any quality you cut due to VBR is gone and forgotten, and CBR 8200 should be suitable for just about any footage from the get-go. Then there's the time saving with CBR too.

So it would seem IMO that CBR 8200 w/ 1536 PCM, or CBR 9000 w/ 448 AC3/MP2 would be the two options that are the most efficient from a number of different perspectives.

[waldi]

What about CQ mode in Procoder? I've encoded the same DV twice. Once using 9000 max CBR and then using 9000 max CQ. The quality seems to be the same when I play it back, but the file size for CQ was almost half of the CBR. Is CBR mode wasting the bits or like Vhelp said that these bits will be useful if you edit and re-encode again?

[DJRumpy]

CQ is a valid option. If you set it to 1:1, the encoder will supply whatever bitrate is required to encode each frame while following whatever limits you impose. If you impose a 9800 kbps max and encode with a CQ 1:1 encode, you end up with an mpeg equivelent to 9800 CBR, only smaller, since not all parts of the mpeg require that much bitrate. This is the option I would suggest you use, rather than blindly throwing bitrate at a source that doesn't need it. Just be sure you know how CQ is implemented on the encoder you use.

[State Of Mind]

I love this thread. You guys are the Triple B (Big Bitrate Boys).