What's more important? Compressibilty or Bitrate?

[yosemite]

hi,

an example for that question:

Think about u have a movie with a tested compressibility of 60%, but the video-bitrate is just 960kbps on 1 CD!

Well, 60% are really good for me, but 960kbps seems to be a little bit less, doesnt it?

what do u think:

What's more important? Compressibilty or Bitrate?

[Swede]

Well, it seems that you haven't understood what the comp.test is telling you.... :confused:
If you imagine a movie that's *completely* BLACK... Nothing else.. Then it would compress *very* good... It would look the same at 1 bit/sec as it would at 1000 bits/sec.. Now, not every movie is completely black, or white, or whatever. Every movie is different, that's why you get different results from the comp.test. It gives you an estimation of how well *this* movie compresses, hence the compression test is of more importance than the bitrate.

[theReal]

For Divx5 with b-frames, 960 isn't low at all (I guess this movie is around 90 minutes? That's not really long either.

The last movie I did with Divx5 and Gknot had a bitrate of ~690 and the compressibility was 59% with b-frames enabled, resolution 608xnnn (can't remember exactly right now and it's not on HD anymore).

If you change the bitrate, your film won't fit on the CD, while the compressibility is an inherent feature of the movie.

[jonny]

What's more important? Compressibilty or Bitrate?


Note one thing: one of the factor that influence the compressibility value is the bitrate, example: increasing the bitrate increase compressibility of the movie.
Anyway sure, compressibility is more important.

[Acaila]

increasing the bitrate increases compressibility of the movie.
Decreases :D

(yes, the comp.check increases, but that's another thing than the compressibility of a movie.)

[jonny]

one of the factor that influence the compressibility value is the bitrate


As you can see i've written "compressibility value".



Decreases :D


Why?



(yes, the comp.check increases, but that's another thing than the compressibility of a movie.)


What is the compressibility of a movie for you?
If you mean "compressibility of a movie" as general concept, i can tell you that no one have set a mathematical definition of this (sorry but i like to play with numbers :D)

The only thing that exists now is the "compressibility value" that take care of:

- the movie
- length of the movie
- bitrate
- resolution
- filters
- parameters used for encode

If you want i can propose you a mathematical method to calculate a "general" compressibility value that take care of the movie only (but this value is USELESS for encode).

[Acaila]

No, you misunderstood me.

I meant:
The compressibility of a movie is the amount it has to be reduced by to achieve the desired size. Which is the opposite of the compressibility test, because that gives the percentage the desired size is of the original.

High compressibility = Low filesize
Low compressibility = High filesize

So:
Increase bitrate = Bigger file = lower compressibility

And:
Increase bitrate = Bigger file = higher compressibility value.

I was speaking in abstract terms.

[jonny]

The compressibility of a movie is the amount it has to be reduced by to achieve the desired size.


If you give this definition what you say is ok.


Increase bitrate = Bigger file = lower compressibility


But don't you think is better to say:

Increase bitrate = lower compression
Increase bitrate = higher compressibility

We are saying the same things... i'm only making a teorical discussion about the correct terminology to use ;).