Is there any way to LOCK xvid bitrate! ?

[birdy]

I would love to be able to lock the bitrate at a desiered value!
Lets say for example at 1600kbps.

Now I would like to know if there is anyway to set MAX or MIN value!
For example for some capturing I do not want to bitrate to fall under 1600kbps even if there is not any movement during a long scene.
And for other I would not want the value to go any higher then 1600 even if there is way lot of motion!

Ofcours same question goes for Divx as I use the ver 4.12 only, but would like to know if bitrate could be locked on it or not!

I don't know if this is possible but incase its not, then this would be something real great to add to the codec!

[Zarxrax]

I don't think its possible to lock the bitrate, but I'm just curious what that would be good for?

[Topaz]

I suppose he could use Constant BitRate but why would anyone whant to use that ;)

[ProfDrMorph]

There's no real constant bitrate encoding in modern MPEG4 encoders. CBR could be useful for streaming but I can't think of other advantages.

[nexus]

How about Max bitrate in the Alt. Curve tab???

--
nexus

[The People's Elbow]

I don't see the point in locking the bitrate anyway, but I guess you could do that if you place the desired bitrate in the 1pass cbr mode and set the cbr values in the debug tab pretty high.
I didn't test it, but it should work i guess.

greetz, Elbow!

[birdy]

well I am prety surprised that non of you guys see any reason for locking bitrate to specific value!
So let me explain why!
what I do is: I capture my movies (direct from digital satelite receiver) to XVID @768X576 with iuvcr. (i know many gonna say its better capturing to mjpeg then comprees) I do that for my important data. But I use my pc as vcr and get amazing excellent quality capturing encoded to xvid in real time.

Now when I use 1 pass mode and set the bitrate to 1600 kbps when I hit capture I get sometimes a movie with arround 21 MB/s with great quality (included pcm 48.000khz 16 bit stereo) and after I compress the sound to mp3 and I get a movie almost as big as VCD but real great quality (not comparable to vcd)

The problem is sometimes the files become 40MB/min, sometimes even more! What I want is to avoid the capture to go higher then a wanted value.
Is this real stupid desire?

Also don't forget I am new to all this, so please if you know better way or have any advice please do not hesitate to let me know and learn, as after all this is all what this forum is about if i'm not mistaken!


@The People's Elbow: (or anyone who knows)
Can you guys please explain to me the 3 values in the debug tab?

Recording delay Factor:
Averaging Period:
Smoother:
Would like to know what dose each one exactly do.

[The People's Elbow]

1st:
Also don't forget I am new to all this, so please if you know better way or have any advice please do not hesitate to let me know and learn, as after all this is all what this forum is about if i'm not mistaken!
- lol, I couldn't find the part in the forum rules which stated that the members have to let "birdy" know and learn stuff ;-) ...by the way: reading the forum rules before talking about them might be cool!

2nd: read the "xvid options explained" guide - the three values might be described there or try to imagine what they do, it's not that hard as their names speak for their function.

3rd: plz tell what you are recording and what you want to do with it (backup on cd/dvd, temp. storage) pure cbr doesnt't make any sense if it's not streaming related. I think a constant quality level is what fits your situation best, but I'm waiting for further informations before I make my final statement.

greetz, Elbow!

[birdy]

Ok as I said before what I really do is Capturing and encoding to xvid in real time from a very good quality source (digital sat).

I really don't care about great compression (filesize).
What I want is to get the best quality and fit about 45 to 50 minutes on one 700MB cd (I mean get a movie on 2 cd's)

And With the price of cd's these days I guess I would prefere to keep high quality and not care about size.

Now the problem I am facing is I never know what is going to happen!
With the same settings I use I hit capture On One Video clip and it becomes 24MB minute (this is with 48khz 16 bit stereo wave) so after converting sound to MP3 I get exactly what I need in size.

But then with the same settings I capture another clip and the size becomes 45MB minute ! This is too Much! I said I wanted quality but not at this size.

So in one word I want to be able to limite my file sizes to arround 24MB/m (including the 48khz wave).

For your info my actual settings are:
1 Pass CBR
Bitrate 1600kbps
Min I frame:2
Max I frame:4
Min P frame:2
Max P frame:4

I also have another question:
I was thinking maybe newer releases and builds of xvid try to make it do better compression! As I don't care that much for size (don't want to fit like most guys a movie on 1 cd) so is there a best build choice for my case?

As for example the best divx codec I found that suits my wanted quality is 4.12! and not the 5.02 or other!

I thank you in advance for your help.
And sorry if I am asking too much! :)

[tripnotik]

Why did you put a max quantizer so low? Try setting at least the max quantizer for P-frames to something higher than 4 and you probably won't get oversized files anymore.

[Zhnujm]

i use the cbr setting a lot and it comes VERY close to the calculated size.
have you tried the default settings ? never used other settings (for cbr encoding)

[Bandung]

A constant bit rate encoding would be ideal for ecncodes done for PDA`s like Pocket PC, etc. Given the limitation on the PDA`s processor`s ability to handle too many bits for video plus audio decoding, constant bitrate would help to prevent spurious frame loss.

[birdy]

well you see, as I said I am not that much into making the file small in size.
What I am looking for is best setting to get MAX possible quality and still not bypassing the 12 to 14 MB/minute (with mp3 audio) size wich is arround 24MB/m with non compressed sound.

I am subscribed to pay per view sat tv and get great movies and just want to archive them for myself each movie on 2 cd's.

[bb]

Originally posted by birdy
For your info my actual settings are:
1 Pass CBR
Bitrate 1600kbps
Min I frame:2
Max I frame:4
Min P frame:2
Max P frame:4

tripnotik gave the correct answer to your question: You need to use higher max quantizers. File size predictability increases if you give the codec more flexibility in quantizers.

E.g. if you set your max quants to 20, the codec will be able to hold the desired 1600 kbps much better than with your value of 4.

bb

[ProfDrMorph]

The best solution to your problem would be something like encoding at "constant quality" ( 80+ % ) and in addition to that define a maximum bitrate. But this isn't possible in XviD ( yet? ).

As for know I suggest you use "CBR" ( which is ABR in fact ) and set all of the CBR options ( Advanced Options -> Debug ) to 0 or 1. IIRC those values represent how the codec smoothes the bitrate curve over time. If you tell the codec to only look at very short intervals and react very fast ( = low values ) it will try to make the bitrate constant. I can't garuantee for anything but it's worth a try! BTW: you shouldn't restrict quantizers too much ( 2 to 6/7/8 should be fine ) because otherwise XviD can't always remove all the details it has to to reach the bitrate you want.

[sam_b]

Would have to disagree with you there. Neglecting streaming, there is little little advantage to be gained in averaging the bitrate over such a small timeframe with a modern codec. Birdy just wants around 1300mb at the end and doesn't care about any instantaneous bitrate. A long averaging time makes the less predictable, you're right, but does nothing for quality. A long averaging time with a 100mb or so headroom should give better quality over the whole film. This should give results slightly similar to a constant quality encode.

All this said, I have not used the CBR option much, and it may simply be broken as I suspect it doesn't get used much by anyone, and your suggested settings may provide a usable workaround.

[birdy]

@ProfDrMorph,

Apparently your solution workes the best for me.
I just tried it leaving my settings exactly the way it was before
and as you said I set all values in debug tab (Reaction delay factor, Averaging period, and Smoother) to "1"

I tried On MTV captured 5 different clips (one of them was very low motion and one VERY high motion) and I was getting an almost perfect CBR @24MB/m (exactly what I wanted) And the quality is very good.

The Datarate would go a little Up and Down, But in the end the Avreg bitrate was stablized and I was no more getting Big values like 45MB/m.

So let me thank you for the valuable advice.
Now I would really Love to know what EXACTLY each of these values do!
Reaction delay factor, Averaging period, and Smoother) they are briefly explained in the codec itself but not enough for me to Understand it correctly.

I also understand that my demands are not the usual demands as almost evryone tries to get better compression (totaly undersandable for internet file sharing and streaming etc) but mine is to get best possible quality.

Guys I LOVE Xvid as with my cd's watched on tv all my friends that see them for the first time think that its DVD ! :)

And only codec that allow me to capture at 768X576 with not single frame drop even in most hogh motion clips is XVID!
It seems to be the less CPU demanding codec!
With divx 4.12 I can go up to 640X480 max.