Here are my findings regarding bitrates and other 3ivx modes:

'Single Pass - Average Bitrate'

Very similar results to the 'constant bitrate' mode that I discussed
discussed previously.

'Single Pass - Constant Quality'

3ivx itself warns that this mode can cause unpredictable filesizes, as
it adjusts bitrate as needed for complex scenes. Bitrate settings seem
to be ignored, so framerate, resolution and the Quantizer Parameter
setting are what you have to mess with to get desired bitrate in this

Dual Pass mode on Tiger has broken bitrate control, as we know
already. Im sure by trying various different settings and resolutions
it is possible to get different bitrates, and hence filesizes, out of
dual-pass mode. But the bitrate control is quite important for this
mode, so this bug is still a problem. Right now with Tiger, I assume
that even if you find the right combination of settings in dual-pass
to get just the right sized video, you'l get a differnt size with the
next video you try to encode, because the entire point of dual-pass is
so it can analyse the contents of the video to see where bits are
needed most.

Short version: Andrews settings work, use single-pass till the bug is
fixed if you are on Tiger. If you get larger files than you want then
change the number in the bitrate box to 600 or 500 or smaller,
otherwise just leave it at the default 6400.


Steve of Elbows

--- In, "Steve Watkins" <[EMAIL PROTECTED]> wrote:
> OK it sstarting to make more sense to me now. Ive done some tests on
> Tiger with 3ivx.
> I started off by using the detailed settings andrew provided. I then
> encoded the same footage at different resolutions and framerates, and
> with the quality slider on different values.
> Findings:
> In "Single Pass - Constant Bitrate" mode, the bitrate you specify is
> just an absolute maximum its allowed to use, not the bitrate thats
> actually used. The actual bitrate is decided by 3ivx, and it changes
> depending on resolution and framerate. The quality slider didnt seem
> to change the bitrate.
> So even when i put 6000 in the box, I got a file that was more like
> 600 kbits. It effectively ignored the 6000, because its such a high
> bitrate that no part of the video was in danger of 3ivx trying to
> encode it at a rate higher than 6000 anyway. 
> When I put a really low value in the bitrate box, 100, it used that as
> a maximum bitrate and of course the footage looked awful.
> Some examples of what bitrate 3ivx footage ended up in during my tests:
> 960x540 25fps = 3800 kbits/sec
> 480x270 25fps = 1265 kbits/sec
> 320x240 25fps = 846 kbits/sec
> 320x240 15fps = 602 kbits/sec
> Hope that makes some sense, I will test other 3ivx modes later.
> Steve of Elbows

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