copying DVD,s

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Dave Watterson
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Re: copying DVD,s

Post by Dave Watterson »

Back to confusion!

Tom and Col: if most DVD players cannot cope with more than 8mbps, surely a VBR system will not let any part of the coding exceed 8mbps.
All it will do is reduce the rate for secenes with less change in them.

Does it not follow that a Constant rate of 8mbps (or just below) is going to match the best bits of Variable and beat the rest of it?

Since extra passes are only intended to work out the variation scheme, what benefit are they for films of "our" length?
tom hardwick
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Re: copying DVD,s

Post by tom hardwick »

I'm with you on this one Dave.
Last edited by tom hardwick on Fri Dec 21, 2012 8:54 pm, edited 1 time in total.
tom hardwick
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Re: copying DVD,s

Post by tom hardwick »

I'm with you on this one Dave. If you have a film of up to an hour then 8 mbps will give you the best picture quality you can expect because of the limitations of domestic DVD players. CBR and VBR will give you exactly the same result because both will be CBR effectively.

Multiple passes and single passes will all come to the same conclusion: use 8 mbps

If your film is over the hour and needs to have a VBR encode, then a multiple pass will give you better picture quality than a single pass.

Tom.
col lamb
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Re: copying DVD,s

Post by col lamb »

Dave

......Tom and Col: if most DVD players cannot cope with more than 8mbps, surely a VBR system will not let any part of the coding exceed 8mbps.
All it will do is reduce the rate for secenes with less change in them.

Yes and No, new Blu ray players should have no problem, newish DVD players should have no problem with discs encoded above 9mbps, older players may have problems

......Does it not follow that a Constant rate of 8mbps (or just below) is going to match the best bits of Variable and beat the rest of it?

No, it just means that (a) very, very fast motion will result in artifacts (b) it will encode at a rate that is not necessary

......Since extra passes are only intended to work out the variation scheme, what benefit are they for films of "our" length?

For one movie on a disc = no benefit due to the movie duration

For a lot of movies on one disc + extensive menus = VBR probably required to enable optimum settings to get all movies on the disc

My own tests show that in most cases 5-6 mbps is more than enough but fast moving scenes may show some artifacts, so 8mbs will give an overkill situation but the highest quality, it will ensure maximum compatibility and also it is easy to remember

Hope I have not added to the confusion but I will say it again, try encoding a short selection of clips at different data rates and see the results
Col Lamb
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Lee Prescott
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Re: copying DVD,s

Post by Lee Prescott »

:? Hi Technocrats:

Baffled I am, indeed I am, re this DVD burning and abbreviations like VRB CRB single, multi passes etc. etc. Perhaps some knowledgeable person can post a simple explanation and perhaps stop using all the abbreviated jargon?

For instance: my Casablanca S-6000 simply burns to DVD or Blue Ray when I tell it to do so. No puzzling questions asked, just does it!

Then afterwards with the multi stack burner IT makes faultless copies X 10 at a time. IT does not ask any questions either - just does as it's told when it's told!

Subsequently having used minus R (-R) printable discs, not one single DVD et al has ever failed to play for anyone! (All of whom are more clueless on this one than I am)! All they want to watch and hear clearly - is The Video!

Hope you all enjoyed a Good Christmas - don't forget, there's a 13 in the coming year!!!

:( Cheers, Lee. (Corporate member of The Baffleodeon!
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Dave Watterson
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Re: copying DVD,s

Post by Dave Watterson »

Hi Lee

We are prone to abbreviations! I try to spell them out the first time I use them in a thread, but that is not the same as explaining them.

The bitrate of a DVD is the amount of information that each second of playing time will reproduce.
For a DVD this is usually between 3Megabits and 9.5Megabits.
The more bits the better the quality of the picture that can be got off the DVD.
But at a higher rate/high quality you cannot store as long a movie as you can at a lower rate/low quality.

CBR=Constant Bit Rate - as the name suggests you tell the burner to store xMbits per second and it will process the entire movie at that quality.
VBR=Variable Bit Rate - here the system stores xMbits per second for scenes where the picture does not change much (such as a talking head) and at yMbits per second for scenes where the picture changes a lot (such as a car chase). In this case y will be towards the top of the acceptable speed range - usually about 8Mb/s while x will be a lower rate such as 5Mb/s. The clever software which does all this uses two passes: first time it looks at all the scenes and decides which ones need the best quality and which will be acceptable at a lower quality. On the second pass it does the rendering and burns the film to disc.

VBR allows a good compromise between overall quality of picture and length of film on the disc.

The Casablanca principle is to hide such technicalities from the user, which is why they are easy to use. In Arabesk (the Casablanca DVD burner program) you will find settings "Three levels are available: Normal, High, and Maximum. Picture quality is determined by the data transfer rate (compression factor). The higher the picture quality, the more storage space is required." Behind the scenes this means the software will use a low bitrate, medium bitrate or high bitrate.

I do not know if the Cassie system uses CBR or VBR.

IF YOU GET THE QUALITY YOU WANT FROM YOUR DVD THAT IS ALL THAT MATTERS

Some editing programs for PCs and Macs do not have default bitrates that seem sensible for film makers. That is why their users need to delve a bit into more technicalities to get that desired quality.

I hope this helps.

Dave
Lee Prescott
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Re: copying DVD,s

Post by Lee Prescott »

:? = still!

Thanks Dave for the in depth explanation.

Of course you are quite correct: Casablanca does present 3 things in regard to this as you state i.e. Normal / High / Maximum.

What happens is IF making a choice it's "engineered" in effect by the length of the video - in other words at Maximum it states it will not fit so of course one drops down to High &c. All to do with quality - I've never had to use "Normal"! In any case but with regard to Casablanca, "experiments" indicate that no one can tell the difference although it's there. The lad next door coming up to 17 years doesn't notice and neither does the 92 years old woman along the road that "Her Ladyship" visits! ....

As is said about "Beauty" - "it's all in the eye of the beholder"!

Anyway: May I wish you all the best for your VRBs CRBs or whatever. I guess
I'll just be at peace and choose to remain "Baffled"!!!

:roll: Cheers.....Lee.
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