jparnold: CBR vs. VBR (apologies for my mistake)

sjj1805 · Post by **sjj1805** » Tue Mar 04, 2008 8:13 pm

Sorry to disagree but if you look "inside" many Hollywood DVD's you will find that they contain more than one copy of the SAME film.
Never understood why they approach things the way some (not all) do where they provide a film in English and the same film in French.
Instead of simply using 2 audio tracks and one video track quite often they have two complete versions of the film.

Many of the films that have been put together more correctly with one video track and several audio and subtitle tracks - as you say contain a lot of fluff.
Sometimes this "fluff" can be as long as the film itself.

Devil · Post by **Devil** » Wed Mar 05, 2008 8:54 am

Have you ever looked at one with a bitrate viewer?

skier-hughes · Post by **skier-hughes** » Wed Mar 05, 2008 11:38 am

I looked at The Matrix,
VBR, 0 - 6,800

2Dogs · Post by **2Dogs** » Thu Mar 06, 2008 12:57 am

Devil wrote:Have you ever looked at one with a bitrate viewer?

Thanks for the suggestion! I downloaded a bitrate viewer, with very interesting results.

You were right of course!

(though I would put the range of typical average video bitrates at 4 - 5.5 Mbps.)

But surely the bitrate calculator could not be wrong?

I would have liked to have had a look at The Matrix, that Graham mentioned, since that is exactly the kind of movie you might expect to use as high a bitrate as possible. Unfortunately, I don't have access to it, so I chose to look at Spiderman 2 instead. It's perhaps similar, in that it uses lots of FX.

The dual layer disc contains 7.25GB of data - so even with previews and fluff, there's some spare capacity.

When I took out all the audio and sub picture streams, it reduced to 5.58GB.

Using the bitrate viewer, the average video bitrate shows as 4950 to 5530 kbps for the five main VOB files. The peak video bitrate was 9450 kbps.

So it's clear that with the audio and subs, the combined peak data rate would be right up to the maximum 10080 kbps allowed by the DVD standard.

Therefore the only way that more disc space could have been taken up would have been by increasing the average bitrate without increasing the peak value. I can only assume that the reason Hollywood doesn't do that is that it would offer no benefit in picture quality.