Different Bitrates for two CD's

[shrekkie]

Hey everyone,
I seem to be having a problem when encoding with xvid. Whenever i rip a 2 CD movie using GKnot, say the average bitrate for the whole movie was 1400 kbps, there's a huge difference between the two cd's after the encoding is done. CD1 ends up with like 1033 kbps and CD2 ends up with 1700 kbps. Any ideas why? I have been getting a lot of movies of late and every rip is turning out to be like this. Any ideas will be appreciated.
Cheers
Shrekkie

[Schlumpf]

More action sequences in the second part?

[Animaniac]

It's VBR for a reason... Some parts require more bits. As you said the average bitrate for the entire stream is what you wanted.

[shrekkie]

yeah i suppose you are right, but how come 2 CD xvid movies my friend backed up have hardly noticeable difference in bitrate, i.e. 1415 kbps for the first one, and 1403 kbps for the second one? I want my movies to be like that? Is that not possible?

[Teegedeck]

NO talk about warez or moviez of any kind, do you hear!?!

[superdump]

One question: does your encode look consistently good? If it does then the codec is doing its job and it doesn't matter.

[mf]

Originally posted by Teegedeck
NO talk about warez or moviez of any kind, do you hear!?!
I think with:
Originally posted by shrekkie
I have been getting a lot of movies of late and every rip is turning out to be like this.
he means that he's been getting DVDs and every rip he made (for personal uses, of course :D) has come out like this.

[shrekkie]

One question: does your encode look consistently good? If it does then the codec is doing its job and it doesn't matter.

Hmm it does look consistently good, the codec is doing it's job, but there's a considerable quality difference between the first and second cd :( so i hope you understand what i mean


he means that he's been getting DVDs and every rip he made (for personal uses, of course ) has come out like this.

Yeah exactly! Thanx a lot for that man!
Cheers
Shrekkie

[Imperial Llama]

Originally posted by shrekkie
Hmm it does look consistently good, the codec is doing it's job, but there's a considerable quality difference between the first and second cd :( so i hope you understand what i mean

That doesn't make any sense. Either the quality is consistent (i.e. both CDs look equally good) or there is a 'considerable quality difference' between the two CDs, in which case the quality is not consistent. :confused:

[Tuning]

CD1 ends up with like 1033 kbps and CD2 ends up with 1700 kbps.
@ this bitrate (>1Mbps) the video needs to be of similar quality except if differs in high motion scenes.

[zulu]

@mf
I think teegedeck was referring to this one:

..but how come 2 CD xvid movies i download have hardly noticeable difference in bitrate..

[Teegedeck]

Exactly. Shrekkie, do me a favour and let this be your first and last offense, OK?

[mf]

Originally posted by zulu
@mf
I think teegedeck was referring to this one:
Ah. Didn't notice that one. Still, even that could be movies he downloaded of DVDs he has to compare his versions against other ones :D. I know I'm fetching far now :rolleyes:.

[yingx2]

Originally posted by mf
that could be movies he downloaded of DVDs he has to compare his versions against other ones :D.

I do that a lot :)

[shrekkie]

this is turning more into an argument of what i posted, i didn't mean to say anything about warez, downloading movies could just be from a friend of mine...and the DVD was owned by both of us of course. Once again, mf thanx a lot for your support in this regard.

And back to the problem, hmm..well i wish i could explain more clearly, but i think it's probably because of the B-Frames? i have enabled it in xvid setup. The movies my friend ripped, had real close bitrates for both CD's, which we were both comparing. I will try a rip sometime with B-Frames disabled and then i will post the results here!

[Teegedeck]

Has anyone mentioned yet that there's absolutely no point in doing this? The second half of the movie, which seems to be more demanding, will look worse than it could. What you're trying to do certainly is 'against the book'. But well, if that's what you want:

If you want to have the same bitrate for both CDs, just encode the movie as two separated halfs, split after half the duration/no. of frames of the movie. Use the 'trim'-function for that, just encode the first half of frames first (two passes, aiming for one CD), then go for the second one. If you don't want to strain your head about the audio, just merge the two halfs temporarily for the muxing, then cut them in two pieces afterwards.

[JimiK]

hey Tee,
why so complicated. The simplest thing is to encode the whole movie using constant bitrate. Then mux the audio and split at the half. Of course the 2nd CD wouldn't turn out so good, but shrekkie had two CD's with the same bitrate for whatever reason it should be this way.
Best regards,
JimiK

[Teegedeck]

... CBR is inherently worse than 2-pass; and this goes especially for XviD's still very simple CBR-algo. Not recommended.

[JimiK]

Of course I know it is? So why is 2-pass better? Because it spends bits exactly where they're needed (at least that's the idea :) ) So it's happening often that the second part of movie needs more bits than the first part (first the roles get introduced a lot of chit chat and blabla. then the real action with running and shooting ;) ) 2-pass can't help the different distribution of bits if it wants to do it's job good. So if you don't want that, you musn't use 2-pass. That's what I wanted to say. And that nobody gets me wrong, my recommendation: if you're not really short of time, you should go with 2-pass and just don't care if there are 70mins on the first CD and 50mins on the second.
Sincerely,
JimiK

[Teegedeck]

I suspected you implied that. ;)

[jonny]

There is a related thread here:

http://forum.doom9.org/showthread.php?s=&threadid=40838

It starts with compressibility but near to the end the discussion goes in a direction similar to this thread (in page 3, last posts, N_F give some interesting data).