Cannot choose a bitrate in QuEnc

[aldaco12]

Hi. I'm having a serious trouble here and I would appreciate a lot some hint.
I'm adding a subtitle to a PAL SVCD MPEG-2 (480x576) with VirtualDub-MPEG2 (a nice VirtualDub's modification which can load MPEG-2 files). After a run, I have my 480x576 AVI file which, to be played in my DVD player, must be converted back to MPEG-2.
I have read this guide, but I cannot find how I can fix a itrate such the QuEnc's output size is about 830 MB (so it fits in a 80' CD-R).
More, it seems that QuEnc cannot keep a definite average bitrate.

This is my detail experience:
I start with a 54' 44" movie (half movie in a SVCD), which turns into a huge (probably I could frameserve it, as well, but I wanted to keep the AVI file to avoid losing extra encoding time to make my checks, in the case the AVI --> MPEG-2 conversion fails) AVI file after using VirtualDub-MPEG2.
I encode it with QuEnc and I use, just for checking it, 2450 kbps in the first page. No advanced option is fixed, except ' 4:3 aspect ratio' .
Auto Max Bitrate is lest selected, as default.
The result is: a 1,252,917,204 bytes file.

I try again. Now I choose: bitrate = 830/1252 * 2450 kbps, and the result gives me 1624 kbps.
I run again QuEnc and now I get a 1,007,249,000 bytes MPEG-2!
Therefore, reducing by 830/1252 = 66% the bitrate I get an output
which is only 1007/1252 = 80% of the previous encode!

What is happening? Am I doing something wrong and I can fix betterQuEnc's seting or, as I read, it hardly keeps the desired average bitrate and, therefore, I'll have to quit trying using it?
I know it's not a common question, often people like to make AVI -> DVD, but I don't have a DVD burner and I prefere to use CD-Rs...
Thanks for your cooperation..

[Mug Funky]

hmm. max rate for SVCD should be something around 2500 kbps (if your DVD player can read faster, you can go higher), and average bitrate to hit 700 megs is 1370 kbps. encode with those settings and you should be right (i'm allowing for 224kbps audio as well).

[aldaco12]

OK, I understand.
I only have couple of problems.

The first, is that the bitrate should correspond also to a movie's length. For example, a 40' movie could fit into a CD with a certain bitrate, say B (and, since a bitrate too low is unacceptable, often ovies are spluit on 2 or 3 CDs, but this is another problem).
The problem is that if the previous sentence is correct (40' @ B fits in a CD-R), a 60' movie, to fit into a CD, should have a minor bitrate, say B' = 2/3 * B (60/40 = 3/2). Therefore the phrase 'the average bitrate to hit 700 megs is 1370 kbps' is incomplete, because if 1370 kbps should be applied to make a 1h movie fit a CD-R, a lesser bitrate should be used, for a 90' movie.

The second is that I canot find a way to fix correcly a bitrate in QuEnc when I encode a SVCD MPEG-2. That is, I see, on the main screen, the box 'bitrate' , which I assume to correspond to the average bitrate. The on 'advanced options' screen I left all as default (expecially 'auto choose max bitrate', because the average should have been just fixed). The results are the following, and surprised me: I encoded a 54' 44" AVI file with QuEnc, leaving, in the main screen Bitrate = 2450 kbps (). The output MPEG-2 was 1,252,917,204 bytes.
I tried again, and I put 1624 kbps (1624=830/1252*2450) and I obtained 1,007,249,288 bytes (meaningless: the ratio of the two bitrates does not correspond to the ratio of the two final sizes).
Third try: I choose 1776 kbps both in the main ('average') screen and this time, in 'advenced options' Max Bitrate: (I unchecked 'auto select bitrate').
The result is again absurd: 390,889,124 bytes. Since I go on using the same movie, the way QuEnc chooses a bitrate goes on being absurd and un-understandable...

I read on some web page that QuEnc has problems fizing an average bitrate. I wondered if someone ad a similar problem and found a posible solution..

[dragongodz]

get yourself a bitrate calculater and save yourself some time. something like fitcd
http://www.sysh.de/

now with your calculations are you factoring in that the audio bitrate is not scaling so the end file size does not scale the same ?

I see, on the main screen, the box 'bitrate' , which I assume to correspond to the average bitrate.
correct.

I left all as default (expecially 'auto choose max bitrate', because the average should have been just fixed)
another case that shows auto max bitrate should be removed. still people using it without knowing what it does.

I read on some web page that QuEnc has problems fizing an average bitrate.
the main problem is undersizing. if you bother to read the main QuEnc thread here you would know that.

[shirohamada]

its the magic of trellis, try switching it off and your undersize problem will go away, well most of the time.
for low bitrate encodes i like trellis on, though it might be slower.

i would say you should cap max bitrate, depends on the player. mine can play up to ~6000kbps pretty well, and the other player i have can barely handle bitrate spikes, for vcd/svcd.